Congratulations Doug, you just crossed 100+ patrons. Glad Jack is now getting top-shelf nip and we're get more vintage amps with mini-concerts. www.patreon.com/uncledougsvintageamps/overview.
Thanks, Craig. It's a milestone we're proud of.....but mostly we are very appreciative of the 102 individuals (at this point) in RUclips Land who stepped up to make Patreon pledges of support. We are also appreciative of the viewers who have made generous donations through PayPal. Due to their generosity, we have avoided the temptation to allow advertising in our videos, and we have been working and investing to produce more and better videos. Viewers who would like to help, please see links in the video description. Thanks !!!!
Tube amps and hotrods... Lord have mercy... I can tell you been practicing your licks Doug... This vid's a classic... After I complete my chemo I plan on becoming a patron. This vid really pulled me through heavy day. Thanks Uncle Doug!
That is amazing, @10:23 I haven't seen a 6L6 like that since I was in the Military back in the 1980s! Out of all my amplifiers my 1947 Magnatone is one of my favorites. Those old amplifiers had the absolute minimum components, pure tone and reliable as heck. This video is great, thank you.
@@UncleDoug I fired up my old Magnatone Troubadour M192-5-S, she is also very quiet. This amplifier was a gift to me from one of my Father's closest friends Bud Brown. Bud is a HAM Radio guy and a great Drummer, he told me he'd had this amplifier since the 1950s (that explains the great shape it's in for an amp being built back in 1947). My goal is to keep it in all original condition and pass it on to my Son. Thank You Again for a great video.
I used to fix some neighborhood cars tube radios, can't remember the tube # but on Chevys we called it the Power tube. We probably were way off on the type. It was a common fault. $1.25 and it works. Everyone thought I was a genius. Dad and I well mainly dad fixed radios we previously picked from trash cans. We gave them away free. Great lesson to me that I could fix anything. Dad's own words to his boys was "Son if you put your mind to it there's nothing you can't fix"
I was actually thinking of making an offer on that exact amp. Was disappointed when ebay emailed me saying it was no longer available. At least it went to someone that will cherish it! Love the videos.
I just finished watching the rest of the video. The car show at the end was awesome. I really appreciate the old cars and the workmanship that goes into the creation of them but I am more of sports car guy so I have a 1986 944 Turbo Porsche (951 in Porsche parlance) Cars and Coffee is one of my favorite things!! Love your videos!!
That is quite a find Doug. Fantastic ! I know quite a bit has been said about the killer bees making their way up into Norrh America; with no solution insight to their restraint. But I never hear a word about the white speckled anomaly that has infested the finish on every vintage radio, TV, phono, and amplifier in North America. The "where is Jack" spot should be a popular segment. Our beagle spent many an hour under her bed, not in it. Very cool find. And yes, it's always the number that is obscured; the rest of the component is usually museum quality. Take care.
Wow, another great video. I've been designing and building amps for many years and the pentode input (EF86) is kind of my trademark. You are the first person I've run across that has described the application of the SG bypass cap in this voltage regulator role. Nobody connects it this way, from the heyday of VOX until present. It makes sense and I'm going to revise my current project to try it. Thanks for the tip Doug.
You're welcome, John. I think the cathode connection makes better sense, since you are referencing the screen to the cathode......not ground, but I have not experimented with it in both positions, to see if there is much difference. If you do, please let us know what you find out.
I tried connecting the cap to the cathode and to ground. The differences were very subtle. It would appear that when you really push the tube it doesn't distort as soon when using it connected to the cathode. Since the tube I'm using (EF86) is also wired with the cathode and suppressor grid connected together, connecting to the cathode connects it to the screen and suppressor grid. I'm going to need to up my intake of smart pills to really understand the difference. The cathode voltage was not affected in any way.
I haven't been seeing Rusty lately I hope he's ok I don't want you to loose your main circuit expert Don't give up on amp videos I consider you a national resource What's make me superior is that I have three cat scans to your one for my electronic projects
Wow Doug,,, what a really neat find on that amp. Never heard of them but the steeles were never a main interest with me. The explanation of that screen cap was very interesting. One of those, " oh it's there but I don't know why, " deals. Nice car show. the 40 Fords always steal my heart. Can't tell you how many models of those I built as a kid. Thanks for sharing pal.
Thanks, Carl. Glad you enjoyed the screen bypass segment. I was not aware of this use of a cap either, until I started studying pentode pre-amp circuits. Many more cars to come in the near future.
Haha, I lost a tooth almost the same way, tied to a doorknob. Also had a wart "treated" by rubbing it with a dirty dishrag which was then buried under the house. Keep the videos coming, they're great.
What a beauty! Many lap-steel makers used a similar pearloid material on their products.. even Fender. I love the look of it. I have a very old lap steel that belonged to Freddie Tavares, who gave it to one of his friends...who in turn gave it to me before he died. The pearloid has unglued from the base wood underneath. Its going to be a big restoration job.
Amp and Guitar sounded great! I didn’t know what a field coil speaker was until you showed me. Man... sure would be nice to have a Roadster to drive around in, while picking up all the Hot Car Show Chicks! 💃🏻⚙️🔩🔧🛢🚘👯♀️👸🏻👩🏻🔧😍🤪
Uncle Doug, is pin 1 (the case) of the 6SJ7 connected to the cathode and if so why? I would think pin 1 would be grounded for electromagnetic shielding. BTW, great explanation of the screen grid bypass capacitor!
Good catch, Don. You're exactly right. In the original schematic 1, 3, and 5 are all grounded. I wired the socket properly, leaving the 1 pin grounded to shield the 6SJ7, but forgot to alter the schematic. I will now do so. Thanks !!
What a joy to watch and the final few Kinks chords really got me (excuse the pun) when you played the intro to All day and All of the Night. The irony is that Ray Davis lives not far from me and I've met him a few times when I've done a few jobs at his Konk studio in Crouch End London England. His brother who originally played those chords I believe lives in Cornwall. That rift is legendary as are all of them by Dave Davis. Currently, I'm working on a 60s Valve (Tube) radio model Bush VHF 81 and following your hints and tips for as good result as I can get. The speaker is in good shape and is an Alnico type and I made a cap discharge wand especially for the job using a 10 watt 470 Ohm w/w resistor! Thanks for your videos and of course your cat-scan Jack!
always like your comments, but i'm most impressed, with your talent !, i've learned a lot, we used to grab old tube amp stereos, on the side of the road!! good stuff!!!!
Just when I thought you were done you bring me right back in!!!!!!!!!!! The contact cement on the speaker did wonders! Also sorry to hear about your Pearloid. I hope my holds out.
That's great to hear, Bill. Due to my difficulty playing any more (due to arthritis in my hands), I have come to almost dread the demo phase of each video, for fear of letting the amp and viewers down. Nice comments like yours put my mind at ease.
I would, but the people I know who are really good musicians are generally involved with other things. Don't worry, I still have a few miles left on the old joints :)
Uncle Doug In any case mate, don't feel you have to put yourself out if the old joints are really playing up some days. The demos are a privilege, not a requirement.
Every new video brings smile to my face :) As for the dental practises, they don't seem to make dads and caps as they used to! ;) Somehow they still seem to fail often :)
That's great to hear, Delatsch. Yes, what was viewed as common sense in the old days would be seen as a felony today......in our sissified, dumbed-down, nanny-culture :)
This is absolutely remarkable. That speaker was in better condition than my thousand-dollar Yuri 809 s after 20 years. The sound is very interesting. I was waiting for you to break into the lead part in The "Walk Don't Run" song. Really cool vibe
I have a dead ringer for this amp, but under the Little Leilani name. Same death cap, same layout, same death cap and cathode bypass cap. It's in even better cosmetic condition, but it had been a home for mice and had much of the internal caps and one of the resistors chewed on. IIRC the main connection to the volume pot was hanging by a thread too. Mine also came with a metal 6L6, and a 6SK7 (though the SJ is more likely original). Whoever originally fixed up the amp got a couple of the components reversed (orange drops) so I had to fix that. Also, you'll get a LOT more volume if you add a screen bypass cap to the 6SJ7, which seems common on schematics but not this amp. FWIW, and great video!
Ah, I just finished through the video. It looks like the screen bypass cap was missing from this one as well? The one in mine was missing or removed. My filter cap can had atrocious ESRs, so it had to go. I also switched to a 5V4GA rectifier which gave slightly more volume and headroom. You know, for my stadium gigs...
No, it had the screen bypass cap, but it's value had deteriorate with age, so I replaced it with a new one. Indeed, the function of the SBC was a major point of emphasis in the video.....I'm surprised that this was not evident during your viewing. Good luck with Wembley.....the groupie situation can get out of hand :)
Dear Uncle Doug, thank you for the videos. I would like to point out that it is good practice to connect the live wall cable to the end point of the fuse holder, never the top outermost sleeve section of the fuse holder. This is for safety as you may accidentally touch the sleeve when replacing a fuse. Thanks
Thank you for your helpful suggestion, Ideal. I would recommend, as even better practice, not to change fuses with the amp turned on......it's like playing Russian Roulette no matter which end is energized, since both ends are hot if the fuse is good.
On a 1960s amp that I converted into a guitar combo amp the electrolytic can cap had good ESR readings like you found. However, the caps had higher than normal leakage current when used at the normal operating voltage. The can actually got hot as the amp was used. So I recommend that old electrolytic get replaced even if the ESR value is acceptable.
Another winner... thanx. Loved the rods as well. Slowly but surely I'm absorbing some tube amp theory thanx to you Uncle Doug. So two questions: What's the biggest most badass electrodynamically equipped amp you've ever seen or know of and have you ever seen an amp with two or more electrodynamic speakers(?). Thanx in advance. the hot rod segment makes me pine away for my long lost '55 Chevy 2 door Bel Air 'post' (283 w/ 4bbl & dragstrip ready 2 speed Slush-A-Matic) in Concours de Elegance (sp?) primer red... Hello to Double '0' Seven Jack and cheers
Thanks, Jonny. That's good to hear. Some very high-dollar vintage radios had electrodynamic 18" speakers, often with their own power supplies. The speakers alone are now worth thousands of dollars to radio restorers. Check Ebay and you may see some.
Hi Uncle Doug. I liked your explanation of the screen bypass cap. This configuration essentially turns this single tube stage into a cascode amplifier, in case your readers want to do further investigation. BTW, I am a bit confused about the connection to the field coil of the electrodynamic speaker. It was my understanding that the field coil is typically placed upstream of the connection to the output stage, so it sees the full current drawn from the B+ supply. Your drawing seemed to indicate that it was connected after the output stage, which would mean that the field coil received very little current.
Thanks, Roiderien. If you check the schematics of virtually every Fender amp from the Deluxe Reverb upward, the B+ goes past the first filter cap, then directly to the center-tap of the OPT. Then the remaining B+ goes through the filter choke and to the remaining tube plates. Apparently, FC smoothing is not needed for the output tubes and this pathway avoids any resistance to the flow of current to the output tubes.
Thanks, Doug. My comment only concerned the connection of the field coil of the electrodynamic speaker. I would expect this coil to be connected upstream of the connection of the B+ to the output stage. If connected after the output stage, the only current running through the field coil would be the preamp current, which would be pretty small. I was motivated to ask this question because the sound from this amp seemed a bit grungy and distorted, and I wondered if this sound quality could be related to the speaker. The other very old amps you have restored have sounded remarkably clean.
I was focusing on the filter choke aspect of the ED coil, Roiderien, but do see your point. I think the fuzzy tone was partially due to the age of the speaker and partially due to the pentode being overdriven by both cathode and screen bypass caps. It sounded like clipping to me. When time permits (I had worked on this amp for four days and wanted to complete the video) I will experiment by reducing or eliminating the bypass capacitance. I will also double check the circuit to be sure the schematic is accurate. Thanks again for your very knowledgeable input.
I double checked the circuit, and you were correct, Roiderien. I had not altered the schematic properly. In reality, the B+ passes by one 20uf cap and then goes directly to the field coil of the speaker......as you suggested. I have amended the schematic to reflect this. Thanks so much for your help in this matter.
Hi Uncle Doug, I hope I 'm not out of line, would you be so kind to Bless me with the titles of the songs you play when making a test run on your restorations. Ever since you Blessed everyone with this latest of many restorations I have been listing to 1950's-1960's music from my past. I have even asked the Surfing Gods of the day to find one of your songs. Thank you from a long time subscriber and thank you for sharing your wisdom with us!
Greetings, F1. Much of my noodling is simply various chords strung together to demonstrate high, mid, and low frequency tones from the amp. The recognizable tunes from this demo would include Tequila (Champs), Walk Don't Run (Ventures), You Really Got Me (Kinks), and a Johnny Cash riff from Folsom Prison Blues.
Hiya Uncle Doug! I thoroughly enjoy watching your videos. I really appreciate your sense of humor. Your teaching style is just great as well. I have one of these little MOTS amps with the "Oahu" name applied to it. I have the matching little lap steel as well. But it's the amp I am contacting you about. Mine has no controls what-so-ever. Not even an "On/Off switch. No volume or tone either. Just an input jack and power cord to plug it into the wall with. I have yet to pull the chassis out (I have mobility issues and do what I can on better days, and sit the rest of the time) to see what's going on there but I'm assuming at this point it's all original. I won't plug it in until I can do it safely. Oh, and it has the Triad Transformer and 6SJ7 pre-amp tube but the power tube is a 6F6. The speaker is a little 6" electrodynamic speaker. So my question is, do you know of a schematic for this little critter? I have scoured the internet and the Magnatone site and found schematics for very similar amps, but never quite hit the bullseye with a schematic that shows no power switch or volume control or one with a 6F6 tube. So if you can point me to any other sources or if you should somehow magically be in possession of one that fits I would appreciate it very much if you would let me know. Please and thanks Dale {8^)
The real early steel guitar amps were built as inexpensively as possible to sell to students, and many were made with no controls whatsoever, just like yours. If it's an Oahu, then it was probably built by Valco, not Magnatone, and an accurate schematic most likely does not exist......however, all simple amps like this follow the same basic floorplan. What do you want to do to it? Do you really need a schematic? In most overhauls involving cap and resistor replacement, a schematic is really not necessary.....jut replace the old components with proper-value new ones.
@@UncleDoug Thanks, Uncle Doug! I really appreciate the reply. Y'know you're right. I probably don't need one. I was mainly thinking about the voltages being written right in there. But if I print a TDS for that 6F6 I can probably figure from there what I need on the plate and grid and so forth. I'm not an expert at this stuff. Not by a long shot. I've always been a really fast learner and handy with my hands and with tools. So when I saw my first Champ kit on the web, I decided to give it try. It looked simple enough and when you get right down to it, with the chassis drilled and labeled for you, and eyelet board, and a layout sheet PLUS a schematic, it's not much harder than a paint by numbers set. If you've had a little experience with soldering, it's not any harder at all. So I've built several now but never really tried to shoot trouble on one yet. I've watched so many of your videos, and some several times, that I feel like I have though. I'm disabled now, with mobility issues mostly. Stamina is a problem too. So I haven't plugged 'er in yet but I will in the next day or so. I keep looking at my stash of parts and think to myself I should send them off to you and Jack. If a mystery care package of goodies is something you might be interested in, shoot me an email at dedwardrice@gmail.com and we can swap contact inf. I'll send you a couple of pics of the little amp. A portrait and gut-shot if you will. {8^) Thanks again!!
6F6's run a max plate voltage of 375VDC, DE, and the maximum plate dissipation is 11W. In a single-ended circuit, the usual PV is about 250VDC. I will contact you by e-mail with a shipping address for the "mystery care package"......which I really appreciate. Thanks so much !!
The speaker was definitely holding it back. I would think it would do really great through a really efficient speaker like a Jensen C12N. I really cool mod would be to find a way to install an external speaker jack using that output transformer....maybe a switching jack that disconnects the internal speaker for the external when you plug it in. Sneak it in back somewhere where it's not seen.
That amp has some nice breakup. Never seen an exterior like that. I remember my grandfather had a 53 Chevy pickup like that. I helped him brush paint it gray to use on his farm. Lol
It is shown at the beginning of the Shock Hazards video, Brad. It's a 1980 Matsumoku Vantage V-695 "Performer" Model with MMK-45 humbucker pickups. I get all sorts of inquiries about the guitar, and I'm never sure if it's because people like the sound it produces.......or want to be sure to never buy one like it :):):)
Doug, Thanks for this and all the other great videos! I have a virtually identical amp (1947-guy climbing a coconut tee on grill cloth) with the absence of the pilot light. It also came with an 8417 power tube instead of the 6V6. It was a northern california 1980's yard sale find my wife picked up, along with the lap steel, for $35. I plan to use it primarily as a harp amp. Unfortunately, it has a very wimpy, somewhat distorted output. I was wondering if I could pick you brain on some possible solutions. Here are some Specs/Repairs/tests: 1. Replaced all the caps and tubes (6SJ7, replaced 8417 with a 6V6 , 5Y3). 2. Voltage on the tube plates: 6SJ7-188v, 6V6-294v; Cathode: 6V6 -15v. 3. It has an 8” electrodynamic speaker with an output transformer mounted to the speaker. 4. Field Coil - measures ~500 ohms 5. Output Transformer primary - 218 ohms 6. Electromagnet does not seem to be “working” 7. 6V6 Bias test, based on your video instructions, original specs showed about 16W plate dissipation, with 500 ohm resistor it was about 12W. (same wimpy volume with either bias setup) 7. Connected the output transformer to a Weber AlNiiCo speaker (speaker field coil still connected) and it sounded great. Unless you have a better idea, I was thinking of replacing the ED speaker with a similar AlNiCo. Few questions on this: 1. If I do this, should I follow the M-197-3-V schematic's 1K and 10K resistors in place of the field coil and the .01uf cap in parallel with OT? 2. Should I replace the OT? 3. What impedance speaker should I use? 4. Are there any other enhancement mods I could make so the amp would be more harp friendly? BTW, there were some, I'm assuming minor, discrepancies between the video schematic and the download schematic: 1. The video had a .05 coupling cap and the download had a .02 coupling cap. 2. The video showed an OT connection before the field coil and the download showed it after the OT connection. Should any of these discrepancies have a significant impact on amp performance? Best Regards to you and Jack and the ferals, Jay McDonald Agat, Guam
If the B+ is going to the speaker field coil, which measures 500 Ohms (so it does have continuity), it should have a strong magnetic field. Without the field coil working, the residual magnetism will allow the speaker to work, but with very low volume.....as yours is. Measure the voltage drop across the field coil to see if any current is flowing through it. If not, figure out why.
@@UncleDoug, Thanks for your reply. Voltage drop is is 32.24 volts, remeasured coil = 530 ohms. I'm assuming this equates to about 61 milliamps. Not sure if this is the appropriate current since I can't find any info online for this Permafllux speaker circa 1947. I checked the speaker again: 1. The line level signal from the signal generator on my iPad amplifies just fine but guitar signal is weak. 2. I checked for coil magnetism again. Instead of touching the coil with my screwdriver a touched the housing and there was indeed some weak "attraction", about 1/4 to 1/3 what I get from a PM speaker. Unless you have any other ideas, I will trace/dissect the signal path and the coil to look for faults.
It sounds like plenty of current is flowing through the field coil, Jay. There must be something wrong with the original EM speaker's voice coil, if a new Alnico speaker sounds great. I suggest replacing the field coil with a standard Fender filter choke, and installing a permanent magnet speaker. Good luck.
Measure your speaker's field coil, assuming that it is intact, to see. They vary from speaker to speaker. If it give a weird reading, then go with 8 ohms.
Hey By George, errr Mr. Uncle Doug rather.... another very cool informative video. I am glad you have had the time to come back from your sabbatical and give us some more of your excellent tube amp documentaries. Forgive my ignorance, but do you happen to offer any of your "Jack Approved" vintage amps for retail sale? You do such a nice job going through them and I would absolutely love to have one of your little practice amps.. should you ever get the urge to let one go.... Thanks!
Thanks, Scott. Glad you enjoyed the video. Yes, I do sell both homebuilt and vintage amps from my collection, mostly to make room (and money) for more :) Pick out a couple and I'll give you the details. If you're looking for a bargain, I still have the J.W. Davis head from this video: ruclips.net/video/RMb17u1GRmo/видео.html and the Newcomb Pathfinder from this video: ruclips.net/video/cwX-KjfCxbI/видео.html
scott@miamivalleyabatement.com The Pathfinder would be a neat addition to my collection as our births are separated by just a few short months. Both examples above would satisfy my intrigue however. Feel free to send pricing on other available models as well. Thanks UD
The pearloid material that covered many of the Aloha and Oahu lap steel amplifiers is a devil of product to try and find currently. Even if one found the stuff I think you'd have to do some very serious head scratchin' to figure out how to install it. I believe it was originally applied with a combination of that purple glue or cement that you mention in the video, and heat shrinking. I've searched long and hard for the stuff and the closest thing I was able to come up with was something called "Drum Wrap" which makes sense since you see many more drums finished in the stuff than amps. FWIW all sorts of colors and widths are available on eBay and elsewhere. If you had an amp that was missing a large swath of the stuff and had to put it right to be able to sleeps nights, you might be able to find a match color-wise. You'd need to have Uncle Doug's considerable snake-eyed concentration ala the J. Geils amp repair to make it work though.
Greetings, DE. I read an explanation of how the pearloid was applied. It was soaked in an acetone-based solvent until the sheets were very soft and pliable, then wrapped on the cabinet with overlapping edges folded around the end grain and sometimes stapled to the interior surfaces. After it dried and hardened, it was how we see it now. I would imagine that the livers of the work crew suffered an early demise from all the toxic solvents.
@@UncleDoug Yikes! I'll bet you're right. Some of that stuff will get into your bloodstream right through the skin and in those days people weren't as aware of that stuff as we are now. Hmmm, now that I've read your explanation of how it was done, I do recall seeing these with staples through the edges inside of the cabinets I on the bottoms. I never considered softening it up that way. All I could see in my mind's eye was the way they shrink-wrap boats for winter storage up here in the north. Yeah, no wonder you can't get the stuff anymore. I've been binging on Uncle Doug videos during the pandemic. That explains my commenting on years-old videos. I hope it's not annoying. {8^)
Thanks, Satch. I will see him in the next few days and will relay your appreciation of his car. He is not at all conceited and will appreciate your comment.
I would love to have seen a demo of the screen-grid bypass cap. I assume since the cap resists changes in voltage that the the screen-grid voltage is the cathode voltage + a certain DC offset?
Awesome video as always Uncle Doug! Really interesting about that Screen grid bypass cap. Would this be more beneficial in a hifi setup than a guitar amp? It would be cool to see an amp rigged up to a spectrum analyser with and without the cap.
Thanks, Harry. Yes, it acts like a mini-ultralinear OPT tap, which would improve fidelity. I wish I had a spectrum analyzer to perform the comparison you suggest. It would be most interesting.
Not to me, but some people would argue that the "outside foil" lead should always go toward the previous tube's plate, effectively shielding the signal sent to the next tube's grid.
Love the old school jokes too many political correct tools out there how are easily offended but was the way thing were when I grew up just love your work and I learn so much your an inspiration for me Thanks for keeping me smiling .
The engine is brand new and the oil is kept scrupulously clean. He drives it almost daily and it recently made a round trip to Austin, TX........about 1200 miles.
Hey Doug I really enjoy your videos thank you very much!! I like so many of our brethren have more projects than time! I have a beautiful 1974 Champ in really great condition that hums and needs fresh Filter caps. I’ve watched your stand alone reverb videos and I’d love to build one as a companion to the champ. Have you seen or thought of adding a tremolo to the reverb? Yea I know didn’t come that way but what an addition tube spring reverb and tremolo all in one. Do you have schematics for such a beast? And where might you buy the transformers?? Thanks in advance. Side questions are you in El Paso? .- .-. -.-
Reverb is the tough part, Jake. Once you have it, addition of tremolo would be relatively easy. If I were designing such a circuit, I'd check some schematics of combo amp tremolos I like and then incorporate the trem circuit into the stand-alone reverb. The power transformer for the reverb might have to be bolstered a bit to cope with the added current draw from the trem circuit.
Nice work on the amp, and great sound. The cigarette burns and paint spots are the perfect touch. :)) Jack was well hidden, almost. :)) Do you think the guy with the white '32 would trade for an '03 Focus? I was starting to get excited about the T bucket when the video stopped. Thanks again for taking time to show your work and tech tips.
Thanks, Andrew. Jack is truly a master of concealment :) I guess that, like an ostrich, since he can't see us.....we can't see him. I'll ask him about the trade, but I imagine he will insist on paying you some difference :) Don't worry, there are about 50 more cars to see.....including several T-Buckets, one of which will knock your eyes out.
Thanks for the video Doug. BTW: Did Jack catscan the amp for any tubers? ;-) PS: What's your opinion on the cost/benefit of using a filter choke in the power supply?
Yes, his scan is rather expensive, but all inclusive :) I like filter chokes. I'm not sure if they affect tone all that much, but they do help create a zero-hum, responsive amp.
Thanks for the video on the cool little amp. I have a question...may be stupid. Can those speakers be reconed? I have Philco radio that once the dust was cleared seems to bem jn surprisingly great shape, except the cone is gone! It looks just like your Aloha speaker with the transformer on it. Thanks for any help!
Yes, you can re-cone electrodynamic speakers in just the same way that permanent magnet speakers are re-coned. Check the video description in my Re-Coning video for a source of all the supplies you would need.
What a coincidence. Jack must have read the same book, because he hides continually......sometimes quite well, and sometimes not so well (as in video).
I love your terminologies say to me that you're like that all the time, take it in the shorts lol I was hoping to see a bit more of the car show you cut it a bit short😔. What did you think of the flying Jimmy I left you last time you interested in one now I bet you haven't tried that coconut oil yet! Do you know any good websites where I can download schematics service manuals free preferably
Thanks, John. I videoed about 60 different hot rods at the show and will include several at the end of each future video, until they run out. This video seemed a bit long to me, so I only used seven. Re the service manuals, you'll have to do searches for them. Generally they are available for a fee, not free.
I have a 12 inch guitar speaker no name only numbers, 6920058, 137-7102, 8 OHMS . Can you tell me what the wattage is? It has a big magnet and a very solid frame. Help !
It's a CTS speaker, Eugene, but unless you can trace the part number (692.....) there is no way of knowing. Generally, the power handling capability is reflected in the voice coil diameter......the greater the diameter, the greater the power capability, but it's only an estimate. My advice is to simply wire it up and blast away. It will either work or not, but either way you're no worse off.
Congratulations Doug, you just crossed 100+ patrons. Glad Jack is now getting top-shelf nip and we're get more vintage amps with mini-concerts. www.patreon.com/uncledougsvintageamps/overview.
Thanks, Craig. It's a milestone we're proud of.....but mostly we are very appreciative of the 102 individuals (at this point) in RUclips Land who stepped up to make Patreon pledges of support. We are also appreciative of the viewers who have made generous donations through PayPal. Due to their generosity, we have avoided the temptation to allow advertising in our videos, and we have been working and investing to produce more and better videos. Viewers who would like to help, please see links in the video description. Thanks !!!!
Glad to see you back, Unc...YT wasn't the same without ya...
Thanks, C7. It's good to be back :)
Tube amps and hotrods... Lord have mercy... I can tell you been practicing your licks Doug... This vid's a classic... After I complete my chemo I plan on becoming a patron. This vid really pulled me through heavy day. Thanks Uncle Doug!
You're welcome, Micheal. Glad you enjoyed it. Best wishes for a full recovery.
always a treat to see one of your videos
Thanks, StG :)
I come for Jack and stay for the insightful amp repair and witty humor of Uncle Doug. Keep up the great work you two! :D
Thanks, Ryan. You are always welcome at Chez Jack :)
Vintage amps with expert technical tutelage capped off with a video of some great hotrods. You've raised the bar again Doug.
We demurely accept your kind accolades, Sluggo :) Thanks !!!!
That is amazing, @10:23 I haven't seen a 6L6 like that since I was in the Military back in the 1980s!
Out of all my amplifiers my 1947 Magnatone is one of my favorites. Those old amplifiers had the absolute minimum components, pure tone and reliable as heck.
This video is great, thank you.
Glad you enjoyed it, HK. You're welcome.
@@UncleDoug I fired up my old Magnatone Troubadour M192-5-S, she is also very quiet. This amplifier was a gift to me from one of my Father's closest friends Bud Brown. Bud is a HAM Radio guy and a great Drummer, he told me he'd had this amplifier since the 1950s (that explains the great shape it's in for an amp being built back in 1947). My goal is to keep it in all original condition and pass it on to my Son. Thank You Again for a great video.
I used to fix some neighborhood cars tube radios, can't remember the tube # but on Chevys we called it the Power tube. We probably were way off on the type. It was a common fault. $1.25 and it works. Everyone thought I was a genius. Dad and I well mainly dad fixed radios we previously picked from trash cans. We gave them away free. Great lesson to me that I could fix anything. Dad's own words to his boys was "Son if you put your mind to it there's nothing you can't fix"
Your father was a wise man, Marlo. I hope you are continuing in his footsteps.
What a perfect amp for recording surf music. Totally lives up to it's name.
Thanks, Jeff. Surf's up !!!
You find the coolest amps! I wouldn't be surprised if Dan Auerbach was a regular viewer.
Thanks, B5. If he is, I wish he would speak up. I am an admirer of his playing style and his equipment.
Uncle Doug - maybe he needs an amp guy.
I was actually thinking of making an offer on that exact amp. Was disappointed when ebay emailed me saying it was no longer available. At least it went to someone that will cherish it! Love the videos.
Thanks, Shawn. It's a small world among us ampoholics :)
I just finished watching the rest of the video. The car show at the end was awesome. I really appreciate the old cars and the workmanship that goes into the creation of them but I am more of sports car guy so I have a 1986 944 Turbo Porsche (951 in Porsche parlance) Cars and Coffee is one of my favorite things!! Love your videos!!
Thanks, Jack. I'm glad you enjoyed it :)
That is quite a find Doug. Fantastic !
I know quite a bit has been said about the killer bees making their way up into Norrh America; with no solution insight to their restraint. But I never hear a word about the white speckled anomaly that has infested the finish on every vintage radio, TV, phono, and amplifier in North America.
The "where is Jack" spot should be a popular segment. Our beagle spent many an hour under her bed, not in it.
Very cool find. And yes, it's always the number that is obscured; the rest of the component is usually museum quality. Take care.
Thanks, James. Glad you liked Jack's segment......he's such a ham :)
What a jewel of an amp. Great brightness in the tone. As always a great video.
Thanks so much, Jim :)
Stumbled upon your channel recently and what a goldmine! Love your videos! Very entertaining and educational. Looking forward to watching more!
Welcome aboard, SB. Thanks !!!
Wow, another great video. I've been designing and building amps for many years and the pentode input (EF86) is kind of my trademark. You are the first person I've run across that has described the application of the SG bypass cap in this voltage regulator role. Nobody connects it this way, from the heyday of VOX until present. It makes sense and I'm going to revise my current project to try it. Thanks for the tip Doug.
You're welcome, John. I think the cathode connection makes better sense, since you are referencing the screen to the cathode......not ground, but I have not experimented with it in both positions, to see if there is much difference. If you do, please let us know what you find out.
I tried connecting the cap to the cathode and to ground. The differences were very subtle. It would appear that when you really push the tube it doesn't distort as soon when using it connected to the cathode. Since the tube I'm using (EF86) is also wired with the cathode and suppressor grid connected together, connecting to the cathode connects it to the screen and suppressor grid. I'm going to need to up my intake of smart pills to really understand the difference. The cathode voltage was not affected in any way.
Thanks for the input, John.
Thanks U.D. 30mins of good vibes.
You're welcome, DB4. Thanks for joining us for the ride :)
I haven't been seeing Rusty lately I hope he's ok I don't want you to loose your main circuit expert Don't give up on amp videos
I consider you a national resource What's make me superior is that I have three cat scans to your one for my electronic projects
Rusty passed away several months ago, Geo. Jack is filling in for him on our new videos.
That's too bad but I know Jack will do a good job
That lil old amp sounds great! Besides the flilter caps i think its good for another 70 years. wow.
Thanks, Lee. I only wish I could last as long as it does :)
Wow Doug,,, what a really neat find on that amp. Never heard of them but the steeles were never a main interest with me. The explanation of that screen cap was very interesting. One of those, " oh it's there but I don't know why, " deals. Nice car show. the 40 Fords always steal my heart. Can't tell you how many models of those I built as a kid. Thanks for sharing pal.
Thanks, Carl. Glad you enjoyed the screen bypass segment. I was not aware of this use of a cap either, until I started studying pentode pre-amp circuits. Many more cars to come in the near future.
Haha, I lost a tooth almost the same way, tied to a doorknob. Also had a wart "treated" by rubbing it with a dirty dishrag which was then buried under the house. Keep the videos coming, they're great.
Thanks, Bobby. We will :)
Another great amp Doug, it's got some volume for a little rig. The car show was a sweet bonus, thanks!
You're welcome, PC. Thanks.....there are about 50 more cars to come.
Brilliantly explained as always, Doug.
Thanks, John :)
What a beauty! Many lap-steel makers used a similar pearloid material on their products.. even Fender. I love the look of it. I have a very old lap steel that belonged to Freddie Tavares, who gave it to one of his friends...who in turn gave it to me before he died. The pearloid has unglued from the base wood underneath. Its going to be a big restoration job.
Thanks, Jennifer. Best of luck with your restoration project.
You would probably get better results by completely replacing the original pearloid with new one. Accordion repair shops can do this service.
So glad youre back doug
Me too, Phil. I missed you guys.
Screen Grid Bypass cap. Great segment!!!
Glad you liked it, Arch :)
A new video from Uncle Doug....NICE!
Thanks, Peder :)
That sounds great! The contact cement seems to have really worked on the speaker.
Glad you liked it, 49 :)
Awesome work uncle doug! Thanks for sharing it with the rest of the world
You're welcome, Damian. Thanks !!!
You're coming up with some true relics....
I've been focusing entirely on amps from the 30's and 40's, Steven. They are really interesting pieces of history and I love working on them.
Amp and Guitar sounded great! I didn’t know what a field coil speaker was until you showed me. Man... sure would be nice to have a Roadster to drive around in, while picking up all the Hot Car Show Chicks! 💃🏻⚙️🔩🔧🛢🚘👯♀️👸🏻👩🏻🔧😍🤪
Thanks, BC. This gathering was about 95% male, but regardless, it would have been nice to have a roadster. It was a beautiful day.
Another great video and...Wow!! What an awesome display at that car show!!
Thanks, T2 :)
Great video as usual, thanks. And always glad you include Jack
Thanks, Demag
I have seen several in Aspen Pittman's (Groove Tubes) collection. Nice! Love your satirical comments, french & the autos.
Thanks so much, Don :)
Uncle Doug, is pin 1 (the case) of the 6SJ7 connected to the cathode and if so why? I would think pin 1 would be grounded for electromagnetic shielding. BTW, great explanation of the screen grid bypass capacitor!
Good catch, Don. You're exactly right. In the original schematic 1, 3, and 5 are all grounded. I wired the socket properly, leaving the 1 pin grounded to shield the 6SJ7, but forgot to alter the schematic. I will now do so. Thanks !!
You are welcome! The polarity of the interstage coupling capacitor is incorrect also.
And the preamp cathode bypass has no polarity.
hay Doug, good job, takes me back to 1970, I use to build and repair guitar amps. I also have the same cat.
Welcome, Sandy. Thanks so much for joining us :)
HI Doug thanks for the interesting amp and quick look at the snazzy cars. Colin
You're welcome, Colin. There are about 50 more cars to see, so stay tuned................
What a joy to watch and the final few Kinks chords really got me (excuse the pun) when you played the intro to All day and All of the Night. The irony is that Ray Davis lives not far from me and I've met him a few times when I've done a few jobs at his Konk studio in Crouch End London England. His brother who originally played those chords I believe lives in Cornwall. That rift is legendary as are all of them by Dave Davis. Currently, I'm working on a 60s Valve (Tube) radio model Bush VHF 81 and following your hints and tips for as good result as I can get. The speaker is in good shape and is an Alnico type and I made a cap discharge wand especially for the job using a 10 watt 470 Ohm w/w resistor! Thanks for your videos and of course your cat-scan Jack!
Thanks so much, Ian, for your interesting input. Good luck with your project.
always like your comments, but i'm most impressed, with your talent !, i've learned a lot, we used to grab old tube amp stereos, on the side of the road!! good stuff!!!!
Thanks, Gene :)
Just when I thought you were done you bring me right back in!!!!!!!!!!! The contact cement on the speaker did wonders!
Also sorry to hear about your Pearloid. I hope my holds out.
Thanks, Justin. It's rare to get a before and after demo, but the contact cement really does pep up the old limp suspensions......and Pearloid :)
Loved the demo tunes in this one Doug!
That's great to hear, Bill. Due to my difficulty playing any more (due to arthritis in my hands), I have come to almost dread the demo phase of each video, for fear of letting the amp and viewers down. Nice comments like yours put my mind at ease.
Uncle Doug Don't put yourself out Doug, maybe bring a friend to do the demos for you?
I would, but the people I know who are really good musicians are generally involved with other things. Don't worry, I still have a few miles left on the old joints :)
Uncle Doug In any case mate, don't feel you have to put yourself out if the old joints are really playing up some days. The demos are a privilege, not a requirement.
Yet another great and fun video! Please keep them coming!
Thanks, Benj. We will :)
Every new video brings smile to my face :) As for the dental practises, they don't seem to make dads and caps as they used to! ;) Somehow they still seem to fail often :)
That's great to hear, Delatsch. Yes, what was viewed as common sense in the old days would be seen as a felony today......in our sissified, dumbed-down, nanny-culture :)
This is absolutely remarkable. That speaker was in better condition than my thousand-dollar Yuri 809 s after 20 years. The sound is very interesting. I was waiting for you to break into the lead part in The "Walk Don't Run" song. Really cool vibe
Thanks, Tim. I would have, like in some previous videos, but the old fingers are a little balky lately.
Great episode, Doug! Thanks!
You're welcome, AQ
great video uncle doug and jack beautiful sound job well done
Thanks so much, Jeff :)
Thanks for sharing your knowledge with us !
You're welcome, Sam.
I have a dead ringer for this amp, but under the Little Leilani name. Same death cap, same layout, same death cap and cathode bypass cap. It's in even better cosmetic condition, but it had been a home for mice and had much of the internal caps and one of the resistors chewed on. IIRC the main connection to the volume pot was hanging by a thread too. Mine also came with a metal 6L6, and a 6SK7 (though the SJ is more likely original). Whoever originally fixed up the amp got a couple of the components reversed (orange drops) so I had to fix that. Also, you'll get a LOT more volume if you add a screen bypass cap to the 6SJ7, which seems common on schematics but not this amp. FWIW, and great video!
Ah, I just finished through the video. It looks like the screen bypass cap was missing from this one as well? The one in mine was missing or removed. My filter cap can had atrocious ESRs, so it had to go. I also switched to a 5V4GA rectifier which gave slightly more volume and headroom. You know, for my stadium gigs...
No, it had the screen bypass cap, but it's value had deteriorate with age, so I replaced it with a new one. Indeed, the function of the SBC was a major point of emphasis in the video.....I'm surprised that this was not evident during your viewing. Good luck with Wembley.....the groupie situation can get out of hand :)
That's what I get for making my first comment during the first few minutes. :o|
Thanks for the lesson and the car show too. 👏🏾
You're welcome, Dominic :)
I guess I'll put a little umbrella in my beer for this one.
.....and maybe put on a nice grass skirt :):)
Dear Uncle Doug, thank you for the videos. I would like to point out that it is good practice to connect the live wall cable to the end point of the fuse holder, never the top outermost sleeve section of the fuse holder. This is for safety as you may accidentally touch the sleeve when replacing a fuse. Thanks
Thank you for your helpful suggestion, Ideal. I would recommend, as even better practice, not to change fuses with the amp turned on......it's like playing Russian Roulette no matter which end is energized, since both ends are hot if the fuse is good.
On a 1960s amp that I converted into a guitar combo amp the electrolytic can cap had good ESR readings like you found. However, the caps had higher than normal leakage current when used at the normal operating voltage. The can actually got hot as the amp was used. So I recommend that old electrolytic get replaced even if the ESR value is acceptable.
Thanks for your input, Stanley.
Great tone for an old amp.
Thanks, Richard. I was pleasantly surprised, especially with the rather small, very old speaker.
The oold aloha amp. Sounds Great
Thanks, Dwight.
Awesome video as always doug! Cant wait to see another or a car video either
Thanks, ET
Another winner... thanx. Loved the rods as well. Slowly but surely I'm absorbing some tube amp theory thanx to you Uncle Doug. So two questions: What's the biggest most badass electrodynamically equipped amp you've ever seen or know of and have you ever seen an amp with two or more electrodynamic speakers(?).
Thanx in advance. the hot rod segment makes me pine away for my long lost '55 Chevy 2 door Bel Air 'post' (283 w/ 4bbl & dragstrip ready 2 speed Slush-A-Matic) in Concours de Elegance (sp?) primer red...
Hello to Double '0' Seven Jack and cheers
Thanks, Jonny. That's good to hear. Some very high-dollar vintage radios had electrodynamic 18" speakers, often with their own power supplies. The speakers alone are now worth thousands of dollars to radio restorers. Check Ebay and you may see some.
some of the best guitar work to date! Oh ya! Nice amp too!
Wow, thanks so much, Greg :):)
Hi Uncle Doug. I liked your explanation of the screen bypass cap. This configuration essentially turns this single tube stage into a cascode amplifier, in case your readers want to do further investigation. BTW, I am a bit confused about the connection to the field coil of the electrodynamic speaker. It was my understanding that the field coil is typically placed upstream of the connection to the output stage, so it sees the full current drawn from the B+ supply. Your drawing seemed to indicate that it was connected after the output stage, which would mean that the field coil received very little current.
Thanks, Roiderien. If you check the schematics of virtually every Fender amp from the Deluxe Reverb upward, the B+ goes past the first filter cap, then directly to the center-tap of the OPT. Then the remaining B+ goes through the filter choke and to the remaining tube plates. Apparently, FC smoothing is not needed for the output tubes and this pathway avoids any resistance to the flow of current to the output tubes.
Thanks, Doug. My comment only concerned the connection of the field coil of the electrodynamic speaker. I would expect this coil to be connected upstream of the connection of the B+ to the output stage. If connected after the output stage, the only current running through the field coil would be the preamp current, which would be pretty small. I was motivated to ask this question because the sound from this amp seemed a bit grungy and distorted, and I wondered if this sound quality could be related to the speaker. The other very old amps you have restored have sounded remarkably clean.
I was focusing on the filter choke aspect of the ED coil, Roiderien, but do see your point. I think the fuzzy tone was partially due to the age of the speaker and partially due to the pentode being overdriven by both cathode and screen bypass caps. It sounded like clipping to me. When time permits (I had worked on this amp for four days and wanted to complete the video) I will experiment by reducing or eliminating the bypass capacitance. I will also double check the circuit to be sure the schematic is accurate. Thanks again for your very knowledgeable input.
I double checked the circuit, and you were correct, Roiderien. I had not altered the schematic properly. In reality, the B+ passes by one 20uf cap and then goes directly to the field coil of the speaker......as you suggested. I have amended the schematic to reflect this. Thanks so much for your help in this matter.
Hi Uncle Doug, I hope I 'm not out of line, would you be so kind to Bless me with the titles of the songs you play when making a test run on your restorations. Ever since you Blessed everyone with this latest of many restorations I have been listing to 1950's-1960's music from my past. I have even asked the Surfing Gods of the day to find one of your songs. Thank you from a long time subscriber and thank you for sharing your wisdom with us!
Greetings, F1. Much of my noodling is simply various chords strung together to demonstrate high, mid, and low frequency tones from the amp. The recognizable tunes from this demo would include Tequila (Champs), Walk Don't Run (Ventures), You Really Got Me (Kinks), and a Johnny Cash riff from Folsom Prison Blues.
Bless you Uncle Doug, the "Walk Don't Run (Ventures)" was the one!!! Thanks again keep it up, you make us feel young again!
You're welcome, F1 :)
Another great video!
Thanks !
You're welcome, Amo.
Hey Uncle Doug, here's an idea: use car parts for the chassis and/or the cabinet of a future amp build. Now THAT would be a good mix of both hobbies!
Thanks, BC. I'll keep that in mind for the future :)
Great work as usual. Keep em' coming!
Thanks, T. We will :)
Hiya Uncle Doug!
I thoroughly enjoy watching your videos. I really appreciate your sense of humor. Your teaching style is just great as well. I have one of these little MOTS amps with the "Oahu" name applied to it. I have the matching little lap steel as well. But it's the amp I am contacting you about. Mine has no controls what-so-ever. Not even an "On/Off switch. No volume or tone either. Just an input jack and power cord to plug it into the wall with. I have yet to pull the chassis out (I have mobility issues and do what I can on better days, and sit the rest of the time) to see what's going on there but I'm assuming at this point it's all original. I won't plug it in until I can do it safely. Oh, and it has the Triad Transformer and 6SJ7 pre-amp tube but the power tube is a 6F6. The speaker is a little 6" electrodynamic speaker. So my question is, do you know of a schematic for this little critter? I have scoured the internet and the Magnatone site and found schematics for very similar amps, but never quite hit the bullseye with a schematic that shows no power switch or volume control or one with a 6F6 tube. So if you can point me to any other sources or if you should somehow magically be in possession of one that fits I would appreciate it very much if you would let me know. Please and thanks
Dale {8^)
The real early steel guitar amps were built as inexpensively as possible to sell to students, and many were made with no controls whatsoever, just like yours. If it's an Oahu, then it was probably built by Valco, not Magnatone, and an accurate schematic most likely does not exist......however, all simple amps like this follow the same basic floorplan. What do you want to do to it? Do you really need a schematic? In most overhauls involving cap and resistor replacement, a schematic is really not necessary.....jut replace the old components with proper-value new ones.
@@UncleDoug Thanks, Uncle Doug!
I really appreciate the reply. Y'know you're right. I probably don't need one. I was mainly thinking about the voltages being written right in there. But if I print a TDS for that 6F6 I can probably figure from there what I need on the plate and grid and so forth. I'm not an expert at this stuff. Not by a long shot. I've always been a really fast learner and handy with my hands and with tools. So when I saw my first Champ kit on the web, I decided to give it try. It looked simple enough and when you get right down to it, with the chassis drilled and labeled for you, and eyelet board, and a layout sheet PLUS a schematic, it's not much harder than a paint by numbers set. If you've had a little experience with soldering, it's not any harder at all. So I've built several now but never really tried to shoot trouble on one yet. I've watched so many of your videos, and some several times, that I feel like I have though. I'm disabled now, with mobility issues mostly. Stamina is a problem too. So I haven't plugged 'er in yet but I will in the next day or so. I keep looking at my stash of parts and think to myself I should send them off to you and Jack. If a mystery care package of goodies is something you might be interested in, shoot me an email at dedwardrice@gmail.com and we can swap contact inf. I'll send you a couple of pics of the little amp. A portrait and gut-shot if you will. {8^)
Thanks again!!
6F6's run a max plate voltage of 375VDC, DE, and the maximum plate dissipation is 11W. In a single-ended circuit, the usual PV is about 250VDC. I will contact you by e-mail with a shipping address for the "mystery care package"......which I really appreciate. Thanks so much !!
Jack has great tail action!
Indeed......he has the most expressive tail in all of catdom.
Thanks l'll keep checking.
You're welcome, Eugene.
The speaker was definitely holding it back. I would think it would do really great through a really efficient speaker like a Jensen C12N. I really cool mod would be to find a way to install an external speaker jack using that output transformer....maybe a switching jack that disconnects the internal speaker for the external when you plug it in. Sneak it in back somewhere where it's not seen.
That amp has some nice breakup. Never seen an exterior like that. I remember my grandfather had a 53 Chevy pickup like that. I helped him brush paint it gray to use on his farm. Lol
Thanks, MW. Welcome to the world of Mother of Toilet Seat (MOTS) :)
"This volume pot was stiffer than the proverbial wedding dick..." That cracked me up!! So glad you're back!
Thanks, Dave. It really was ;)
Seems i am developing a second passion, awesome cars! Thanks for sharing :)
You're welcome, Sebastiaan. Be careful, it's an expensive hobby/obsession.
"Stiffer than the proverbial wedding dick . . ." That's a classic. I laughed out loud at that. You ought to take your show on the road.
Thanks, TM. It seemed appropriate at the time :)
One of these days can you show the guitar you're using in the demo portion of the videos? Just curious. Don't recall having seen it before.
It is shown at the beginning of the Shock Hazards video, Brad. It's a 1980 Matsumoku Vantage V-695 "Performer" Model with MMK-45 humbucker pickups. I get all sorts of inquiries about the guitar, and I'm never sure if it's because people like the sound it produces.......or want to be sure to never buy one like it :):):)
Nice! Not too fussy about the sound though. Nice rides!!
Thanks, Robert :)
Doug,
Thanks for this and all the other great videos!
I have a virtually identical amp (1947-guy climbing a coconut tee on grill cloth) with the absence of the pilot light. It also came with an 8417 power tube instead of the 6V6. It was a northern california 1980's yard sale find my wife picked up, along with the lap steel, for $35. I plan to use it primarily as a harp amp.
Unfortunately, it has a very wimpy, somewhat distorted output. I was wondering if I could pick you brain on some possible solutions.
Here are some Specs/Repairs/tests:
1. Replaced all the caps and tubes (6SJ7, replaced 8417 with a 6V6 , 5Y3).
2. Voltage on the tube plates: 6SJ7-188v, 6V6-294v; Cathode: 6V6 -15v.
3. It has an 8” electrodynamic speaker with an output transformer mounted to the speaker.
4. Field Coil - measures ~500 ohms
5. Output Transformer primary - 218 ohms
6. Electromagnet does not seem to be “working”
7. 6V6 Bias test, based on your video instructions, original specs showed about 16W plate dissipation, with 500 ohm resistor it was about 12W. (same wimpy volume with either bias setup)
7. Connected the output transformer to a Weber AlNiiCo speaker (speaker field coil still connected) and it sounded great.
Unless you have a better idea, I was thinking of replacing the ED speaker with a similar AlNiCo.
Few questions on this:
1. If I do this, should I follow the M-197-3-V schematic's 1K and 10K resistors in place of the field coil and the .01uf cap in parallel with OT?
2. Should I replace the OT?
3. What impedance speaker should I use?
4. Are there any other enhancement mods I could make so the amp would be more harp friendly?
BTW, there were some, I'm assuming minor, discrepancies between the video schematic and the download schematic:
1. The video had a .05 coupling cap and the download had a .02 coupling cap.
2. The video showed an OT connection before the field coil and the download showed it after the OT connection.
Should any of these discrepancies have a significant impact on amp performance?
Best Regards to you and Jack and the ferals,
Jay McDonald
Agat, Guam
If the B+ is going to the speaker field coil, which measures 500 Ohms (so it does have continuity), it should have a strong magnetic field. Without the field coil working, the residual magnetism will allow the speaker to work, but with very low volume.....as yours is. Measure the voltage drop across the field coil to see if any current is flowing through it. If not, figure out why.
@@UncleDoug,
Thanks for your reply. Voltage drop is is 32.24 volts, remeasured coil = 530 ohms. I'm assuming this equates to about 61 milliamps. Not sure if this is the appropriate current since I can't find any info online for this Permafllux speaker circa 1947. I checked the speaker again:
1. The line level signal from the signal generator on my iPad amplifies just fine but guitar signal is weak.
2. I checked for coil magnetism again. Instead of touching the coil with my screwdriver a touched the housing and there was indeed some weak "attraction", about 1/4 to 1/3 what I get from a PM speaker.
Unless you have any other ideas, I will trace/dissect the signal path and the coil to look for faults.
It sounds like plenty of current is flowing through the field coil, Jay. There must be something wrong with the original EM speaker's voice coil, if a new Alnico speaker sounds great. I suggest replacing the field coil with a standard Fender filter choke, and installing a permanent magnet speaker. Good luck.
@@UncleDoug Sounds like a plan. Thanks for the advice. BTW, What impedance speaker should I use, 4 ohm or 8 ohm?
Measure your speaker's field coil, assuming that it is intact, to see. They vary from speaker to speaker. If it give a weird reading, then go with 8 ohms.
Hey By George, errr Mr. Uncle Doug rather.... another very cool informative video. I am glad you have had the time to come back from your sabbatical and give us some more of your excellent tube amp documentaries. Forgive my ignorance, but do you happen to offer any of your "Jack Approved" vintage amps for retail sale? You do such a nice job going through them and I would absolutely love to have one of your little practice amps.. should you ever get the urge to let one go.... Thanks!
Thanks, Scott. Glad you enjoyed the video. Yes, I do sell both homebuilt and vintage amps from my collection, mostly to make room (and money) for more :) Pick out a couple and I'll give you the details. If you're looking for a bargain, I still have the J.W. Davis head from this video: ruclips.net/video/RMb17u1GRmo/видео.html and the Newcomb Pathfinder from this video: ruclips.net/video/cwX-KjfCxbI/видео.html
scott@miamivalleyabatement.com The Pathfinder would be a neat addition to my collection as our births are separated by just a few short months. Both examples above would satisfy my intrigue however. Feel free to send pricing on other available models as well. Thanks UD
I will respond by e-mail, Scott.
The pearloid material that covered many of the Aloha and Oahu lap steel amplifiers is a devil of product to try and find currently. Even if one found the stuff I think you'd have to do some very serious head scratchin' to figure out how to install it. I believe it was originally applied with a combination of that purple glue or cement that you mention in the video, and heat shrinking. I've searched long and hard for the stuff and the closest thing I was able to come up with was something called "Drum Wrap" which makes sense since you see many more drums finished in the stuff than amps. FWIW all sorts of colors and widths are available on eBay and elsewhere. If you had an amp that was missing a large swath of the stuff and had to put it right to be able to sleeps nights, you might be able to find a match color-wise. You'd need to have Uncle Doug's considerable snake-eyed concentration ala the J. Geils amp repair to make it work though.
Greetings, DE. I read an explanation of how the pearloid was applied. It was soaked in an acetone-based solvent until the sheets were very soft and pliable, then wrapped on the cabinet with overlapping edges folded around the end grain and sometimes stapled to the interior surfaces. After it dried and hardened, it was how we see it now. I would imagine that the livers of the work crew suffered an early demise from all the toxic solvents.
@@UncleDoug Yikes! I'll bet you're right. Some of that stuff will get into your bloodstream right through the skin and in those days people weren't as aware of that stuff as we are now. Hmmm, now that I've read your explanation of how it was done, I do recall seeing these with staples through the edges inside of the cabinets I on the bottoms. I never considered softening it up that way. All I could see in my mind's eye was the way they shrink-wrap boats for winter storage up here in the north. Yeah, no wonder you can't get the stuff anymore. I've been binging on Uncle Doug videos during the pandemic. That explains my commenting on years-old videos. I hope it's not annoying. {8^)
@@dale1956ties Not at all, DE. We appreciate your time and interest.
Enjoy your videos
That's good to hear, CW :)
Spastic Octopus safely removed : ) U R the Best
He was tamed, with the help of some solder and an iron !! Thanks, Rob :)
Congratulations on your Patreon. Also, tell your friend his white Ford looks awesome (he probably already knows this)
Thanks, Satch. I will see him in the next few days and will relay your appreciation of his car. He is not at all conceited and will appreciate your comment.
Uncle Doug. How much would you take for Jack. I need a friend here in my shop. My dog wont visit more than a few minutes.
Jack's rental fees, while astronomical in amount, are actually quite reasonable when compared to the GNP of Europe.
I would love to have seen a demo of the screen-grid bypass cap. I assume since the cap resists changes in voltage that the the screen-grid voltage is the cathode voltage + a certain DC offset?
I'm not sure how it could be demonstrated, David.....perhaps a with and without comparison? I think your understanding is correct.
Great amp! Can't believe it's that old. Many thanks that you let us participate your autophobia as well!!!
Thanks, MO. You are always welcome on our excursions :)
Awesome video as always Uncle Doug! Really interesting about that Screen grid bypass cap. Would this be more beneficial in a hifi setup than a guitar amp? It would be cool to see an amp rigged up to a spectrum analyser with and without the cap.
Thanks, Harry. Yes, it acts like a mini-ultralinear OPT tap, which would improve fidelity. I wish I had a spectrum analyzer to perform the comparison you suggest. It would be most interesting.
Hi the coupling capacitor show the polarity is that matter at all. Thank you.
Not to me, but some people would argue that the "outside foil" lead should always go toward the previous tube's plate, effectively shielding the signal sent to the next tube's grid.
Love the old school jokes too many political correct tools out there how are easily offended but was the way thing were when I grew up just love your work and I learn so much your an inspiration for me Thanks for keeping me smiling .
You're welcome, Bee. Thanks for your nice comments.
Kind of surprised that 32 gets drove. Clear valve covers are neat, till they get dirty. The stud girdles and rockers, all clean also.
The engine is brand new and the oil is kept scrupulously clean. He drives it almost daily and it recently made a round trip to Austin, TX........about 1200 miles.
Hey Doug I really enjoy your videos thank you very much!! I like so many of our brethren have more projects than time! I have a beautiful 1974 Champ in really great condition that hums and needs fresh Filter caps. I’ve watched your stand alone reverb videos and I’d love to build one as a companion to the champ. Have you seen or thought of adding a tremolo to the reverb? Yea I know didn’t come that way but what an addition tube spring reverb and tremolo all in one. Do you have schematics for such a beast? And where might you buy the transformers?? Thanks in advance. Side questions are you in El Paso? .- .-. -.-
Reverb is the tough part, Jake. Once you have it, addition of tremolo would be relatively easy. If I were designing such a circuit, I'd check some schematics of combo amp tremolos I like and then incorporate the trem circuit into the stand-alone reverb. The power transformer for the reverb might have to be bolstered a bit to cope with the added current draw from the trem circuit.
I guess the logic was the larger the volume knob the louder the amp would go!
Yes, and as stiff as the pot was, you really needed the extra leverage.
Nice work on the amp, and great sound. The cigarette burns and paint spots are the perfect touch. :)) Jack was well hidden, almost. :))
Do you think the guy with the white '32 would trade for an '03 Focus? I was starting to get excited about the T bucket when the video stopped. Thanks again for taking time to show your work and tech tips.
Thanks, Andrew. Jack is truly a master of concealment :) I guess that, like an ostrich, since he can't see us.....we can't see him. I'll ask him about the trade, but I imagine he will insist on paying you some difference :) Don't worry, there are about 50 more cars to see.....including several T-Buckets, one of which will knock your eyes out.
Thanks for the video Doug. BTW: Did Jack catscan the amp for any tubers? ;-)
PS: What's your opinion on the cost/benefit of using a filter choke in the power supply?
Yes, his scan is rather expensive, but all inclusive :) I like filter chokes. I'm not sure if they affect tone all that much, but they do help create a zero-hum, responsive amp.
Very cool.
Thanks, Bart.
Hey Uncle Doug, I was wondering if you knew how the watt reduction knobs and switches work on Orange amps
I don't, LD. They are a bit too "modern" for me. Perhaps another viewer can help.
Thats me Doug. The beginner who wants to build an amp.
Well then here's a nice schematic for you to follow, Hack. With a fresh 10" speaker, this circuit would sing like an angel :)
Nice playin"!!
Thanks, Robert :)
ooowow!!
Thanks, Malcolm :)
Nice eBay snag! The only thing that tipped me off was the lump in the carpet, it could've been that lost sock that jumped out of the dryer.
Thanks, Jeff. I didn't notice the lump or the tail.....but I guess that's why he doesn't feel the need to hide very well :)
Another award winning episode and the title card at the end takes the cake. haahha
Thanks, Blue :)
Thanks for the video on the cool little amp. I have a question...may be stupid. Can those speakers be reconed? I have Philco radio that once the dust was cleared seems to bem jn surprisingly great shape, except the cone is gone! It looks just like your Aloha speaker with the transformer on it. Thanks for any help!
Yes, you can re-cone electrodynamic speakers in just the same way that permanent magnet speakers are re-coned. Check the video description in my Re-Coning video for a source of all the supplies you would need.
Uncle Doug thanks so much! Appreciate it!☺
uncle doug dear sir, would i be at all right in guessing those valves in cases could have been army surplus at that time the amp was made.?
It's a possibility, Ralph, but there were no markings on them to indicate it.
When my son was little I would read him a book called "Finding Jack", all about finding a cat called Jack who was somewhere in the house.
What a coincidence. Jack must have read the same book, because he hides continually......sometimes quite well, and sometimes not so well (as in video).
I love your terminologies say to me that you're like that all the time, take it in the shorts lol
I was hoping to see a bit more of the car show you cut it a bit short😔. What did you think of the flying Jimmy I left you last time you interested in one now
I bet you haven't tried that coconut oil yet!
Do you know any good websites where I can download schematics service manuals free preferably
Thanks, John. I videoed about 60 different hot rods at the show and will include several at the end of each future video, until they run out. This video seemed a bit long to me, so I only used seven. Re the service manuals, you'll have to do searches for them. Generally they are available for a fee, not free.
I have a 12 inch guitar speaker no name only numbers, 6920058, 137-7102, 8 OHMS . Can you tell me what the wattage is? It has a big magnet and a very solid frame. Help !
It's a CTS speaker, Eugene, but unless you can trace the part number (692.....) there is no way of knowing. Generally, the power handling capability is reflected in the voice coil diameter......the greater the diameter, the greater the power capability, but it's only an estimate. My advice is to simply wire it up and blast away. It will either work or not, but either way you're no worse off.