Bell & Howell Filmosound 385 Amp Conversion for Guitar Use, Part 1
HTML-код
- Опубликовано: 9 сен 2024
- This compact amp was built into Bell & Howell movie projectors in the late 1950's and is one of the favorites for conversion to guitar use. Its tone is said to mimic that of early Fender tweed amps. In this video series, we will discuss the step-by-step conversion of this amp into a guitar-friendly version and experiment with its tone capabilities. The Part 1 video will include 1.) A detailed look, inside and out, of an original unmolested amp. 2.) the conversion into a basic guitar amp and the difficulties associated with the process 3.) A baseline sound test for comparison with the results of circuit modification.
If you enjoy our videos, please subscribe and read the notice below:
Since maintaining this YT channel and our FB page has become a "full time job", and in response to the suggestions of several viewers......Rusty, Jack, and I have signed up for a site on Patreon, named "Uncle Doug and Rusty". If you like our videos and (hopefully) helpful advice, then please consider becoming a patron. Thanks :) Here is a link to our site: www.patreon.co...
![Megan Thee Stallion - Neva Play (feat. RM) [Official Video]](http://i.ytimg.com/vi/TpYTyAaTRts/mqdefault.jpg)
You make everything seem so easy and matter of fact. It's because you are a tube amp Jedi.
You are such an inspiration. Jack and Rusty have no idea that they live in the shadow of a giant!
Wow, thanks so much, JZ. I will relay this information to Rusty and Jack.....maybe it will inspire them to behave better :)
I second that.
Thanks, W4 :)
Actually Jack and Rusty are ware of their situation. It's just that they pretend in order to keep the easy food coming.
Excellent video. You describe the process very well and provide a good basic conversion. So many tech guys don’t have the awareness to step it out clearly for beginners.
Thanks, R&R. I'm glad you enjoyed the video.
The smaller speaker jacks were needed to prevent the school's "expert" from connecting the school's only microphone to the speaker output. That mike might never be replaced during that school year. Yes. I was my school's "expert". Fortunately I had some knowledge of sound equipment from my dad, and knew better than to make that mistake. Later on, though, as the A/V repair tech for my county's school system, I developed a fond appreciation for B&H's wisdom.
Thanks for that insight, Bill. It makes good sense.
Uncle Doug, you rock. Rusty is a good catcher and jack is very stealth-like. Waiting for part 2.
Wow, three out of three.....this must be a good video :) Thanks, Dave :)
Brother Doug (I'm too old to call you uncle...), you teach me ALLOT about being a better teacher, as well as almost watching myself puttering in my lab and shop. If i traded my old diesel 4x4 for a jeep and dyed my old lazy dog "rusty" things might get kinda twlight zonish. I teach kids in Mexico music, guitar and amp repair as well as building custom amps and guitars for amigos. If you ever get to the Puerto Vallarta area, i just moved, after 20 yrs near PV, to the beautiful pine covered mountans about 2 hrs from the PV airport. Mi casa tu casa. Anyone who gives of their time and knowledge like you do is a brother indeed....Come film a video in my lab. I have a huge pile of "project" amps and you'd like the tools and parts to complete almost anything. Or just chill, and pick a little classic rock. Thanks for all of the inspiration. ..Brother "RIFFIN"
Wow, that's a tempting offer, MM. It sounds like you have a great lifestyle....I too am partial to mountains and pine forests, but I've spent the vast majority of my life in the desert Southwest. Maybe someday Rusty and I will come visit :)
We too lived near Pecos NM for years back in the 80's. We have plenty of cactus and desert type critters to keep us from getting too nostalgic. C'mon down. Rusty and Chucha would no doubt get along fine. Later amigo...mi casa tu casa.
Again, a tempting offer. Thanks so much :)
Videos like these make RUclips so awesome :) Great work, informative, and well explained.
Thanks so much, Jeff :)
Just wanted to share that as my first ever tube amp conversion project I got my hands on a B&H Filmosound 156 amp. Unfortunately it was in a flood and all of the wiring and other components were completely rotten and covered in mold. Surprisingly, all tubes tested perfect. So instead of trying to repair, I ended up re-wiring it as a Valco/Supro Supreme 510-1B amp. The tube compliment is almost identical with exception of 6SC7 in Valco and 6SL7 in B&H. With some minor adjustments to component values I was able to get it done, although cramming all of it in such a small chassis was not fun :).
Anyways, it sounds amazing and looks great!!
Good heavens, Artom, you certainly started off with a challenging first project. I am impressed that you were able to successfully convert it to a completely different circuit......especially in such a cramped chassis.
Great project!
So just scored one of these little bad boys!!! Soooooooo stoked!
Congratulations, YT. Let us know how it turns out.
@@UncleDoug unfortunately i missed this comment Uncle Doug :( Its been sitting waiting for its time to shine. I also have a 15" rola speaker i would love to make a combo out of it 😀
@@YeeThirty Good luck with the project :)
Reminds me of my first guitar amplifier. I used the alt. inputs on a 1970ish sears and Roebuck stereo console.
I remember those Alt Inputs well, Mr. S. Sort of a poor man's Silvertone guitar amp :)
WOW !! That's virtually a frenzied activity level for Rusty - smile !!
He gets pretty wild at night around feeding time :)
God how i love this show and the cast this season cant be beat. The daytime emmys are going to be a sweep this year!
Rusty won a daytime Emmy last year for best supporting actor (sometimes) on four legs.....ironically, it was presented by Bob Barker :)
hahahahahahhah whoo hiyooo
Another video of great interest! This amplifier design was pretty common for 16mm film projectors. The octal socket that is located to the right of the output transformer is for the Photo Cell (photo tube) it is used for picking up the light pulses on the optical sound track. There also should be another connector on the chassis for powering the exciter lamp which supplies the source of light to penetrate the optical track. I would leave the 5Y3GT as the rectifier. installing solid state diodes will certainly elevate the B+ and more so since the amplifier is rated at 117VAC, and today's line voltages are anywhere between 120-127 VAC...something to ponder :) I've worked on quite a few of these for schools and churches. Ampro was another popular projector with similar amplifier designs. Sadly, film isn't as popular these days. Looking forward to seeing/hearing the results to follow. :)
Thanks for the info, Frank. I intend to keep the 5Y3. I'm too much of a tube junky to change to SS.
Just picked up an old flimosound 302 tube amp and am planning on converting it. Loved your video.
Thanks, Alex. Good luck with your project.
Welcome and thank you
Great thanks and regards to Jack and Rusty. Nice thinking about a tremolo section. Thanks for sharing.
You're welcome, WK :)
A timely project as I have two of these needing conversion. I was thinking a lunch box head. Can't wait to see what you come up with. Thanks !
You're welcome, VW. I guess these are even more popular than I thought :)
Jack is really awesome! I have a little black cat. She seem to like helping when I work on my studio and guitar gear. Rusty is also super cool!
Thanks, Grady. There is nothing like having a furry companion to help in the workshop.....and in life. Rusty and Jack both say "Thanks" for your nice comments.
Great video Doug, many thanks. Jack and Rusty have excelled themselves.
You're welcome, SS. Glad you enjoyed it.
another good one,, cheers Rusty Jack And Doug
Thanks, Paul....from the gang at Rusty's Garage :)
Hi Uncle Doug. Thank you.
All the best.
B
You're welcome, Bobby. Our best to you.
Thanks for your videos uncle Doug.
You're welcome, KT :)
good catch, Rusty!
Arf !! ;)
Doug, happy trails. I had a second chassis with all the goodies. Replaced all the caps and readied for guitar work. Boom, nice and loud, little hum and great tone.... and I have not messed with thew NFB yet. Not anemic at all. It's M-2 BTW. Maybe its the tubes or fresh caps. This amp rocks right out of the box. Now for the Uncle Doug trem trick.
Greetings, Angelo. Glad to hear that the B&H amp worked out OK. Good luck with the tremolo addition.
Uncle Doug, I'd never question your expertise. Wondering why you didn't drill out the old speaker jacks in place? Keep 'em coming. You, Rusty and Jack are the best!
Thanks so much, WJ. I guess I could have done that, but the idea didn't occur to me until after I had removed the jack from the chassis. Also, I use a drill press for work like this, and it's hard to set up an amp chassis in a milling vise :)
+Uncle Doug A belated Thank You!
You're welcome, WJ.
Great video subject, Doug. I'll be watching! Thanks!
You're welcome, Bart.
Can't wait to hear what it will sound like. Great video!!!
Thanks, Chris :)
Another very promising project! I can't wait to see the next part!
Thanks, PoB :)
Greetings from Chile, well I'm in USA...nice job I just wanted to say thanks for sharing you knowledge with us.
You're welcome, Cristian.....glad you enjoyed it :)
I've got a one or two very old Film O Sound amps removed from projectors.
Amazing stuff Doug!
Thanks, Amo.
Has usual Douglas, I’m intrigued. I’ll definitely be captivated with the progression of your latest amplifier conversion project.
Bell & Howell - with the advent (and later demise) of the Philips N1500, and 2000 systems, Sony’s Beta, and JVC’s VHS; and now we have mp4, we don’t hear about, or see, many of their projectors like we once did.
Occasionally, a customer, to whom we may have repaired their TV, or radiogram, requested us to take a look at their defective home projector. Though I personally have never worked on home cine-projection equipment, I have very vague memories of looking over the shoulder of a fellow service tech and seeing him working on a Bell & Howell amplifier that incorporated the following valve complement: EZ80, EF86, and EL84.
If I’m not mistaken, I’m now starting to think as to whether that amplifier was, or was a rendition of, the Mullard 3-3 amplifier.
I also have vague memories of seeing a projection amplifier - as to whether it was a Bell & Howell, I’m unable to say - with a lead connection that plugged into a separate audio unit that was most certainly a Mullard 5-10 amplifier. Have you ever encountered either of those types of Mullard amplifier?
From the depths of my memory, I’m vaguely recalling reading about Bell & Howell now operating, amongst other business ventures, within the world of corporate finance???
73 Phil.
Greetings, Phil, and thanks for your interest in this latest project. This is the only projector amp I have ever worked on, and it is quite challenging due to the compactness and high component density. I would expect any product of Mullard to be of high quality, however, and would love to get the opportunity to work on one.
Wow really cool amp Uncle D, I wish I could find one, looks like a great way for a conversion. Good to see Rusty agian, thx bud. looking forward to part2.
Thanks, Tony. I think they are generally available on Ebay. You could do a search. Good luck.
I want one!!! Great job! Keep up the good work.
They're often available on Ebay, Mike. Thanks for your nice comments.
Good to see Rusty has still Got It! I' m in the beginning stages of repurposing my shop and will be delayed on the '57 5E3 refurb. This video is right up my ally, and will give me more info on how to make that little amp sing like it should. I think Jack was trying to play hide and seek! Thanks again for another JEWEL! Thankz
You're welcome, ATL. If I can ever get the numerous filter caps replaced, the fun should commence :)
I love the way you put together your videos Doug :)
Thanks, Hydro. This one went pretty smoothly, without a lot of editing.
That is a good thing, saves loads of time in the end.
WONDERFUL! Thank you.
this is fantastic brother. much appreciated!
You're welcome, SG :)
I just saw another video where a guy played a guitar through a stock one of these. It sounded beautiful !!
So naturally, I looked up some for sale on the web. 1500 and 2500 dollars canadain. Woah.. I'll be sticking to gutting old radios. But.tyat is a great.little amp. I'll have to look up that builder !
I should have bought a bunch of them back when they were $250 to $300 apiece :)
That loooks like more fun than a person is allowed to haha! I just can't do much about this right now but some day soon-ish I just gotta finally come around to learn this, if nothing else for proper amplification for my funeral. And no, I'm not that old but with the speed my electronics plans are proceeding I might as well start in time haha!
Awesome job on the video. Love the black cat.
Thanks, Charles.......from both of us :)
BTW Doug, a big thanks for the HD versions you post. I have been able to select screen grabs at hi-rez, which are very helpful. My own 385 has run into a snag, my PT is blown. I am looking at the Classics Deluxe PT as a replacement and should be back on track soon.
You're welcome, Angelo. Glad you like the HD. Best of luck with your 385 repairs :)
I remember the 16mm projectors and the suitcase size amplifiers projector built into suitcase halves, in the schools in the late 50s.
The tone and speaker (the other half of the suitase) was quite decent. These 16mm film units went around to the public schools in my area of Canada on an infrequent basis and the large film cannisters were produce by the NFB (National Film Board of Canada) and were for information purposes approved by the school boards.
Occasionally, the picture framing and the sound got out of sync as the sprocket holes were at the end of each frame and if
the threaded film loop was not set right, the drive sprocket could easily skip a hole, and the movie had to be stopped to rethread the sprockets on the projector. Talk about wow and flutter! The sound track was a variable width optical sound track.
"For half a century cinema sound systems were licensed to either RCA or Western Electric, and motion picture producers elected to license one or the other, or even both
The sound on the 16mm was variable width optical track to represent the amplitude of the audio signal. Because of it's
low frequency response and low noise threshold, there would have to be a optical to sound signal conversion done
The extra tube (6V6) oscillator was an early switched mode power regulator (I guess) to provide the 4.75 volts required
by the exciter lamp. In those days, they didn't have all the sold state regulators that we can use today to provide 5.0 Volts
DC.
The 6v6/5y3 with black plates were characteristic of the tubes made by RCA in those days.
Lol! Jack is a "riot. " he forgets about the long tail that always sticks out giving him away.
Wow, thanks for the very informative review of projector amps, SC. We really appreciate it. I believe most cats, including Jack, learned their concealment techniques at the Ostrich Institute. Their mantra: "If you can't see them....then they can't see you".
Interesting so far, looking forward to part 2. Good to see Rusty inspired by the 50's movie projectors, reminds him of his childhood maybe? ;)
Thanks, FB. Yes, as a pup, he was quite a fan of the cinema, particularly Lassie, Rin Tin Tin, and Old Yeller.....but we still both cry during the last one :)
Uncle Doug, this is a really great video. About 7 years ago I purchased a At Mars Amps 15 watt head. The amp was a Bell & Howell conversion. The tube compliment is pretty much the same as your 385, minus the 5879 pentode tube. I played the head through a 2X10 Dr. Z cab, usually with a Telecaster. What a glorious sound! Regrettably, I sold the amp. If you get a chance, check out the At Mars Amps site. Aesthetically and sound-wise, the amps are way cool. Keep up the good work!
Thanks, Bruce......I will check them out.
Just some info here, That one 6v6 oscillator usually runs at 40 kc and the output of it feeds the exciter lamp that supplies the light that goes through the sound track on the film, that 40KC is at about 3 volts or so. The tube socket labeled PEC is for the Photo Electric Cell tube that takes the varying light and changes it to a varying electrical output, that output goes to the 5879 tube for preamp and filtering circuits to filter out the 40 KC bias signal and I believe that the sound was emphasized at recording and DE emphasized in this amp. Also the amp output transformer impedance is either 16 ohm (1 speaker) or 32 ohm (2 speaker) And yes these amps are physically difficult to work on due to compactness of amp design like you said. I believe that later models MAY have an 8 ohm impedance output transformer. ------ John A Bellas KC2UVN
Thanks for the interesting info, John.
Actually, the dual speaker output is 8 ohms. It carried over an amp design from the 40s that was nearly identical but with a bigger pair of transformers (and different speaker connectors). The 12AX7s functions were handled by 6SL7s and the 5879 function was done with a 6J7 tube. If you think the 385/399 amp is crowded you should see the one used in the 179, 185, or 285 (although most of those came with a different series tube amp, the 14 watt amp being an option.)
The dual speakers were wired in parallel. The standard speaker was 16 ohms, either a 12" in a separate case or a 5x7" in the projector proper (next to the lens opening) or a 6" on a removable door.
Something to watch for: There was also a model 384 which looks almost exactly like a 385. The amp looks the same but has lower output. You can tell these apart by looking at the projector mechanism. The 384 lacks the forward/reverse switch.
Be Aware!: The 385/399 amplifier used a lighter power transformer that was somewhat prone to failure, especially compared to the one in the earlier models. In fact, B&H ran out of them for replacement in only a few years. To repair a 385/399 amp we were forced to fit the power transformer from the earlier models which was still in plentiful supply, not an easy task. The 385/399 original was smaller and stood on spacers. The other transformer had to fit lower into the chassis and it was really work to get it in there.
If you find a good 385/399 amp and remove the oscillator tube and photocell it should lower the failure rate but you must change out those electrolytics.
Awesome! Can't wait for part 2
Thanks, TK.
Great stuff Uncle Doug, the only suggestion I have is when you install power cords, I always take the hot side (Black wire) from the AC cord to the fuse first. This way the whole device is protected even if there is a power switch problem. Fusing on the Hot side is also recommended since the Neutral (incoming AC white wire) is the same potential as the incoming AC ground, a fuse on the neutral side would not protect against a hot to ground issue. Just my 2 cents.
Thanks for your input, Rex. I base my wiring preference, with the power switch first, then the fuse, both in the hot lead, so that he fuse is not energized when the power is off, which can prevent a shock hazard when changing fuses. I have never seen or heard of a power switch causing a short circuit. If I gave the impression, in the video, that I prefer the fuse in the Neutral wire, then I apologize for the confusion. In every other video and at every opportunity, I have advocated placing the fuse in the black "hot" lead, after the power switch.
Thank you very much !
You're welcome, OB :)
so cool. there is a shop here in victoria bc ive recently had the pleasure of patronizing. the owner showed me an old projecter project the customer was determined to use for guitar. . i just think thats beyond cool.. kemper is awesome and the epitomy of tone reproduction. but i STILL prefer oldschool. its how it feels as much as it sounds for me as a player.
Thanks, Scott. I am certain that the majority of subscribers and viewers would agree with you.....there is no substitute for tube tone.
Hey folks! If you mod these try using sozo coupling caps. .02 or Jupiter. the change in tone can be heard and sounds great.
15k NFB. Resistor is what I've seen on Austen hooks. But the adjustable pot you put on yours is very smart.
Btw I've experienced different voltage level through them. I like 375 - it should end up at 375 once you move the projector portions of the circuit because it pulls about 20 to 30 volts even when not being used. Pull them! The bump in voltage 350 to 375 made a huge difference. More headroom, more full tone, a little more punchy. (The video on my page is a 350v filmosound. It has been changed a lot since then
Thanks for the tips, Steve.
Larry Urbanski of Urbanski Film sells the correct Switchcraft # S-250 speaker plug to fit those jacks.
Thanks, Ken.
This is really cool. Cant wait to see the pt. 2
Thanks, HA. We haven't heard from you in a while. Welcome back :)
This one is really going to be a cool one. Im interested how difficult the cap job will be. Also how you get the right tone out of it looks challenging.
Thanks, H. Yes, the cap job is a real nightmare.....taking about 10 times longer than with regular amps. Tone mods will follow once I get it working again.
Its going to be fun to watch.
The amplifiers in the model 285 and 179 projectors were sometimes shipped with "hot chassis" (AC/DC) amplifiers and some had regular power transformer amplifiers.
I have seen and heard of the "transformerless" models, Ken. I guess they were buried inside the projector and theoretically untouchable.....so not a huge shock hazard......but definitely a problem when they are extracted and converted to guitar use.
Hallo .
Uncle Dog nice project i like that
Bertus
I'm glad, Bertus. Thanks :)
Neat project.
I prefer to see the power cord go to the fuse first, so that everything else is protected.
I'd remove the old power socket and out a switch in there for impedance selection.
Thanks, Tim. There are those who prefer that the fuse is not energized when the amp is turned off, for safety while checking or changing fuses. Also, I have never seen a power switch that required protection. We all have our own preferences, however, and I appreciate your sharing them with us.
My reasoning is that the switch is more likely to be broken than the fuse post, so the fuse should protect the switch. For safety, make sure that the power cord goes to the rear terminal of the fuse post.
Even if the black "hot" wire is connected to the bottom terminal of the fuse holder, the upper end of the fuse will still be energized if the fuse filament is intact. People will get a false sense of security by simply switching off the power and can still get a nasty shock from the energized fuse. Also, in 40 years of repairing amps, I have never encountered a power switch that caused a short circuit or could deliver a shock.....i.e. needed protection.
That's interesting. I just saw another video with that amp, and the tone and volume knobs were in the opposite order.
That's the beauty of building your own amp, Guy.
All right Rusty,, good boy,,,,, Hey Doug, this looks like a real nice project. I have a Wollensak that I am going to amp convert in the future so I will definitely be paying attention for tips and tricks. Thanks.
Carl
You're welcome, Carl, and best of luck with your conversion project.
FYI, although not a secret, it is not generally recognized that prominent manufacturers have their own three-digit 'manufacture's code.' 188 on a tube shows that it was made by GE. 274 on a tube shows that it was made by RCA. 312 on a tube shows that it was made by Sylvania. I do not remember all of them, but I'm confident that the RMA code is available elsewhere on the web.
Very helpful information, James. Thanks for providing it :)
Very cool project Uncle Doug! This got my immediate attention because up until 2002 I was employed by the Postal Systems Inc division of B&H at their original location on Pratt Ave. on the north side of Chicago as an engineer. While they got out of the camera and projector business as technologies changed, there was all kinds of legacy products and information at the old facility. Unfortunately long gone now. It was torn down and turned into a shopping center. Looking forward to the progress on this project.
Thanks, JC. It would be nice to have found a whole warehouse full of these jewels back then.....but now we have to hunt them down, one at a time, on Ebay.
+Uncle Doug I understand. I have a friend who worked on the camera and projector products before my tenure. He did design work on projector products. Haven't talked to him in a long time but I will send him an email at the last address I had for him about your project. He would find this repurposing project very interesting. Unfortunately, the facility only had examples of the legacy products B&H made, no stock per say.
If he responds, please let us know what he thinks, JC. It would be very interesting to hear from one of the original designers of these products.
+Uncle Doug his email address failed, but I will see if I can look him up through my network. The dating of this product predates both his and my tenure at B&H. He worked on some of the last projector products produced then did much of the microfiche work finally moving into postal automation where we met. It is always interesting to me to see things being done with B&H legacy products. All the best.
+jcmcclain57 spoke with his grandson, he is currently in the hospital. Unsure of his condition, but I can tell you he would be very interested in following your project on this amplifier. When I talk to him, I will let him know about the Filmosound Project.
A trip through my local St.Vincent de Pauls' yielded one of these for $15 ...
i knew my Uncle Doug would know what to do with it - - -
🤞 Oh - i won't risk it , but an Astute set of Notes to give my amp man
will expedite a worthy conversion 👌
Congratulations on the find and good luck with the conversion, RR.
Hi Uncle Doug.
I seem to remember those projectors from my school days. They could produce a rather loud and full sound when needed. There was nothing anemic about those amps, if I remember correctly.
Sure wish had your luck finding these gems.
Greetings, SluggO. Yes, the volume and overall tone are quite good, especially for a projector amp. I didn't find this. It was very generously sent to me by a viewer who wanted to provide a good topic for some videos....so I guess we all owe him a debt of gratitude.
Great video Uncle Doug! Geez that little amp is as cute as a mouses earole! - I never knew it was so small - but with quite a nice sound despite the nfb frequency response limiting. And you're gonna make it sound even better? I can't wait for part 2! Just wonderful mod ideas with the tremolo, speaker jack & adding a case around it - with a speaker too? Please hold off long enough for me to go grab a coffee & a packet of macadamia short bread bikkies!
Glad you're enjoying the videos, Neville.
Hey Doug I've run into those smaller Switchcraft Jacks before. They are "Switchcraft .21inch .206 connector S580 littel plug" if you do a search on ebay they're on there.
Thanks, but I converted them to 1/4", AL.
Hi Uncle Doug & Rusty, I hope all doing good. Talk about a pocket sized amp, just about the size of an old tube radio chassis, about 3" x 9", plus , minus. Looks like another good conversion amp. Lookin' for part 2 when ready. Take care, C.
It's a real devil to work on. I'm still changing the filter caps....what a nightmare.
Good stuff Doug. I just got an old Stereo Amp made by Knight... ( or perhaps it was a kit) that I want to covert to a guitar amp. This video gave me the basics for sure.I have not found a schematic yet, but working on it.
Thanks
Ron
I think almost all Knight electronic products were kits, Ron. I built my share of them during my early years. Best of luck with your conversion. Let us know how it turns out.
Do you have a good schematic you can share that could be used to convert this one? It has 6 tubes, (2)6SN7GT (1)6SLN7GT (2)6v6GT and (1)5Y3GT/G. All older but basic stuff.... circa 1955... thanks Doug
I don't keep a big file of schematics, Ron. Generally, I just do a Google search for the one(s) I need and then keep a copy on file. So far, I have never worked on any Knight equipment. If all else fails, you can draw your own. It's a good learning experience.
Good idea Doug thanks. I would like to do an old Fender circuit in this, perhaps I will make this a fender Champ Model 5F1
You're welcome, Ron.
Rusty does a good Steve McQueen impersonation. :)) I've learned something from every one of your videos, so this should be a high density treat. Since cats can't see red, Jack must think he's blending in nicely.
P.S. Tremolo chassis almost ready for paint.
Greetings, Andrew. I think we'll all learn something from this series, since I've never worked on one of these before and it's rather challenging. I'm glad the project is going well for you. Be sure to let us know how it turns out.
Hey Uncle Doug I know this video was a couple years ago but just as a note, my 1959/60 Ampeg J-12 has a 6SL7 tremolo circuit that is one of the the best I’ve ever heard! I haven’t really looked closely at it but there is a schematic in the box I can take a picture of
I'm not sure what "box" you are referring to, Tommy (?)
Uncle Doug just a little New England colloquialism... I was referring to the cabinet, sorry about the confusion. It’s on the back panel, as usual for vintage Ampegs. I’ll make a video run through of it so you can check it out, I love the tremolo, and I’d like to think I’m somewhat of a ‘tremolo hound’- it’s one of the main reasons I bought the amp!
Thanks, Tommy. You can post the schematic on my Facebook page: Uncle Doug's Vintage Amps. All us tremolo hounds look forward to seeing it :)
ruclips.net/video/7Xf-TTNexM4/видео.html
I'm excited to see what kind of tremelo circuit you install.
So am I, Lincoln :) Considering the lack of space within the chassis, it will be a challenge.....but hopefully possible.
Hello Uncle Doug, I have come across a vintage truetone lap steel amp that looks very much like the twin brother of the Oahu that you restored previously. I has a 5y3, 6v6, 6j7, 6sn7 tube complement. I have a schematic which I downloaded from the internet which is nearly identical except for the 1st stage preamp tube, however, the tube characteristics are nearly identical. The amp was working briefly, but now there is no sound. I pulled the chassis, and it has had some repairs in the past, some amateurishly done. The cabinet and speaker are in very good condition and the speaker looks like it was re-coned not long ago..but .good job, the voice coil is intact. I am a retired IBM engineer and I have the skills to save it but, unfortunately, not the time. I now have a second career in Property Management which consumes me. So, the amp has been just sitting year after year, waiting for attention. I am not interested in putting it out on ebay. I do not need the money. An amp such as this which has survived this long, deserves some respect, and deserves to live a little longer. There is only one person besides myself who would be qualified and that's you. If you are interested, I will send you the amp as a project at no charge.....giving it to you. Maybe if and when you restore it you can put a short video out there so I can see it has a second life. If you would you be willing to give this homeless amp a good home, tell me where to sent it. Regards, Robert (branta@ibmr.us)
I truly appreciate your generosity and would gladly accept the homeless Truetone amp, repair it, and feature it in a video. I will contact you by e-mail to arrange the shipping. Thanks again.
i saw the 2 big filter cans and thought hmmm i know its tubes but maybe there is something i can learn from this as far as diagnosing my peterson solid state model 400 strobe tuner.you will like this,the problem with the tuner is that the strobe wont spin well the unit contains 2 big can capacitors 2000 mfd at 50vdc with the same type of this what looks like burnt plastic oozing out of the bottom.when you explained about the increased current flow increased heat and the tuner uses a driver circuit with solid state transistors in a push pull fasion(i think) the increased current flow would be enough to melt a big old hole in one of the transistors especially if someone had left it on to long like let me just leave it on while i go get a pack of smokes and i will come back and pick up where i left off.i really dont like learning the hard way but the burnt electrical smell that was floating into the living room by the time i got back told me that uh oh something aint right.upon entering the room where it was still on i could see that the motor had stopped spinning but everything else was still on.the good news i can turn the strobe by hand so the motor is still good.i took electronics in college a long long time ago never got a degree because i could not read or write and do algebra but i understood how electricity flowed in a circuit and that has never left me it was nice to get back into it for a 50 yr old college drop out i just wanted to say thanks for making this channel and posting these videos by the way the turner was my dads and he still complains at how much it cost him in 1972
You're welcome, PJ. Good luck with your project.
Hey Uncle Doug, I have nearly the same model as your B&H amp. I have looked mine over and decided it would be better to harvest these parts and build them in a more friendly chassis. And yes one of my output tubes will red plate too. The parts will make a very nice amp in a better chassis/housing. Let me know if you want to compare notes. Best regards
Your decision to relocate the parts makes good sense, PT. The close proximity of components really makes this little jewel a devil to work on. What did you do with the NFB loop ?
I have a B & H Filmosound 302 with a slightly different tube line up and it's PT is separate and connected by an umbilical cord. It is still stuffed in a very cramped chassis, making it far more difficult to work on. Mine has a 12AX7, 12AY7, and a 12AU7. These same parts could be used in something like the Hoffman 6V6 Plexi plans. I have made one of these, with some slight modifications, and it sounds great to me. There are also a number of Fender designs that could be copied with these parts. But in any case, I think it is easier to work on/troubleshoot/modify or repair a guitar amp that is built in a roomier chassis along the lines of the chosen, Proven to work well, layout and design. They also seem to appeal to buyers better if built in a better chassis/housing.
Your alternative-circuit amp sounds interesting, Paulin, and I agree that these compact-chassis amps are tough to work on. Using the parts to make an amp, using a Hoffman or Fender circuit, in a roomier chassis makes good sense.
Great video as usual :)
Those waxies will be leaky...
Go Rusty!
Thanks, Michael. I have a feeling you're probably right. Rusty says "Hi".
I haven't tried it yet but apparently you can melt the guts out of those with a heat gun and install a modern cap inside. Finish it off with some brown hot glue over the ends and you can keep the waxy look :)
Howdy back to you Rusty
That sounds like a good trick for a valuable vintage amp, Michael, but this circuit is hard enough to work on without adding any complications :)
Great video. The amp already sound pretty good to me. I can't wait to see the end results.
Rusty is a good catcher. If you could only teach him how to throw it, you all can get a good hand ball... Or, should I say in this case, hand/mouth ball game going on.
Thanks, Grant. The second video was posted today, so you can check it out at your convenience. Meanwhile, Rusty and I will play some hand/mouth ball :)
Yay!!!
Glad you like it, Joe :)
Doug, Check out Austen Hooks, he has been modding these ,studio guitarist Tim Pierce has one.
I will, VW. They really are popular :O
Glad you are working on this amp, Uncle! I have the exact same, and would like to get it to sound more sparkly, maybe Fender "brownface" Princeton-like? It can get loud as-is. I have do the grounded plug,, and rewire the speaker jack like you did. Have the original male jack.
I have successfully replaced all the filter caps and removed the neon bulb and oscillator circuits so far, Bill. The tone and tremolo are next, so stay tuned.
As a teen, mom got me a Realistic MIJ guitar, but no amp. But dad had a B&H 16mm Film-o-Sound projector with 12" remote Jensen speaker. So I had to sneak when dad was at work, not bad considering the amp Radio Shack sold for the guitar. There was a heavy wire with six pin Jones plug. I think the speaker cab had a secondary amplifier, not sure. I'd like to find one. Don
There is indeed an empty socket (besides the 6V6 oscillator) that could be for the cable you describe, Don. I believe these are often available on Ebay. Good luck.
What? Just Tremolo, no Reverb? And I thought you liked a challenge. I'm sure I saw half a square inch of vacant chassis there some place. I tried scaling the chassis against the 5Y3 socket and came up with about 10 by 5 inches? Also it might be of interest to some viewers to know that when some tubes, 5Y3 is one, are mounted horizontally certain pins have to be in horizontal plane. I think it applies to directly heated rectifiers, while with indirectly heated ones like 5AR4/GZ34 and 6AX5 it doesn't seem to matter. I don't know if it is concerned with a hot filament sagging and contacting a plate causing all hell to break loose as I have no experience with this method of mounting tubes. Looking forward to seeing how you fit everything into that tiny chassis. Good luck.
I really wanted to install a 3-tube Magnatone Vibrato effect and a built-in Leslie speaker, Jeff, but Rusty bit my ankle and brought me back to my senses. You're right about some tubes being fussy about orientation, but the majority of them are not, according to the tube handbook. This is why I dared to install the 12AX7 in my Trem-O-Boost (previous video) horizontally. I too wince at the mental image of a saggy filament flapping around like a windsock in a hurricane causing havoc akin to birth of the Frankenstein monster and/or the Hindenburg disaster. Thanks......I'll need it :)
After setting the bias to 335 at pin 3, I noticed the 385 schematic calls for 335v on both 6v6gt plates, but the 6v6gt tube data sheets call for 285v on the brimar sheet or max voltage of 315v on the Tung Sol. that may be why one of my old original B&H tubes is redplating. ???
Cat, the term "bias" refers to the plate dissipation of the output tubes, not the voltage applied to the plate. If one of your 6V6's is red-plating, as one of mine was, it's due to too much current flowing through the tube. 6V6's can tolerate plate voltages over 400VDC, but too much current flow really harms them. You will probably need to change one or both of the 6V6's so that the pair has matched plate current, and then properly bias the amp so that the plate dissipation is within proper limits. Good luck.
@8:42 - The cat was too much 🐈
Glad you enjoyed it, Francisco.
I have a 1946 Filmosound that I was using for guitar. One day when I turned it on smoke rose up from under the input transformer where the doghouse with the filtercaps is situated. I think it was the caps and I hope to replace them. Because of the "ratsnest" compactness of it I haven't been able to get any qualified person to take it on.
Good luck with the repair, Bruce. As you said, these small amps are really crowded with components and tough to work on. I can see why the local folks are reluctant to do so.
Do you have the amp with 25L6's? That was the common one with a "doghouse".
I have the exact same amp on my bench right now! Bought it for 20$ at the flea market with all the original tubes. At first I found that this amp sounded incredible with the right speaker, but I agree that the sound could be improved. I am curious of what you will do! The modifications I did so far were to use concentric knobs to control bass and treble separately and I also needed to replace the electrolytics. I can confirm that it was a not a fun operation.
The octal socket on the right side of the amp is for an 930 magic eye tube. You need to remove this tube in order to use it as a guitar amp.
What a great coincidence, GG. I had no idea that a magic eye tube went in that socket.....I thought it was for a cable to connect the amp to the projector. I am in the midst of replacing the electrolytics and am convinced that being burned alive with soldering irons may be more fun. On a more positive note: the negative feedback loop has a big impact on tone and volume.....or the absence of it. Check it out.
Will do! About that magic eye tube, I think I used the wrong term here. It's more like an infrared sensor (less exciting isn't it?). I think it was used to read the audio signal, or to mute the amp when there was no image.
I'm eager to see how you managed to replace the electrolytics. I myself couldn't find cap cans of the same sizes and same values so I hacked the thing and managed to fit a JJ cap can in the unused 6V6 socket. It's ok from the outside but ugly on the inside :)
I'm still struggling with the electrolytics, mainly because I'm replacing each value with an individual axial cap. It's much like trying to build a ship in a bottle that is filled with barbed wire and rattle snakes.
Hahaha! That will be fun to watch ;)
More fun than doing it, I'll guarantee :)
Hi there, great videos, everyone says so and they can't all be wrong. I've one concern which comes up all the time in your work. It's your fixation for Rusty Jacks! Is this not taking the original vintage ethic too far or am I just being silly? There's a subject for a whole new series right there. All the best Uncle Doug, you're making a lot of people happy, motivating them to better things and giving them a chuckle in the process.Thank you very much.
You're welcome, Mr. A. Indeed, over the years, I have found that Rusty Jacks are by far the most reliable and entertaining of all workshop accessories. Every shop should have a pair :)
Hi Uncle Doug. Thanks for continuing to make these great videos! They're so informative and really laid out well for the layman who is interested in learning more about tube circuitry. I have a video request: If you haven't already covered the topic elsewhere, could you do a video about output impedance and speaker mismatching? This has always been a bit of a mystery to me. I understand that mismatching in the higher impedance direction for an amp is ok and won't harm the amp or tubes (e.g. amp expects 4ohm and is wired to a 16ohm cabinet). But in the lower impedance direction can either damage the amp and/or wear tubes more quickly. Also confused about what an amp actually "sees" if it has a pair of output jacks that simply say "4ohm" across the top as my '65 TRRI does (one labeled as "ext. speaker" and the other as "int. speaker.") Does that mean each jack expects a 4ohm load independent of the other, or that its a total of 4ohm, and if so does it treat the two as in series or in parallel? How does one determine this? Thanks again and keep up the great work!
You're welcome, Jeff, and thanks for the very nice comments. I have posted videos on impedance and output transformers, if you check my video list. A short answer to your inquiry is that matching the impedance "expectations" of the output transformer is by far the best option. The OPT matches the resistance/impedance of the tube plate(s), which are high voltage/low current to the resistance/impedance of the speaker, which is low voltage/high current.
The primary (tube) impedance depends upon the secondary (speaker) impedance. Using a half-impedance speaker will change the tube impedance to one-half also, which causes the OPT to flow too much current (harmful) and produce sub-optimum tone. Using a double-impedance speaker will double the tube impedance, resulting in reduced OPT current flow and possibly harmful high voltage levels in the tubes and OPT primary.....as well as reduced volume and tone.
Yes, you can generally "get away" with one step of impedance mismatch (4 Ohm speaker instead of 8 Ohm), but, like cheating on your wife or driving while drunk, just because you generally "can" get away with it doesn't mean you should.
With the 5879, this is closer to a Gibson GA-40 Les Paul or GA-20T Ranger amp from the 50s.
Yes, which puzzles me why its tone is likened to a tweed Fender Deluxe. Perhaps just hype, but I guess we'll see.
You've inspired me to give this a shot. I found this exact model for sale locally. What would you say the power output would be?
That's good to hear, MC. A pair of 6V6's in push-pull should be good for 10 to 12 Watts. Best of luck with your project.
iirc, fender was using triad transformers in their tweed amps.
I got same model amp, I'm trying to clean the sound cause when I play through it has some humm sound, I can't wait for next video. .
If you can determine the frequency of the hum, it will help you find out its source. See my video on two types and sources of hum, 60Hz and 120Hz.
+Uncle Doug thanks for your response, I'm going to follow your videos in this convertion, yo ser how turns this amp. I wish you where in the area to let you do mine, I like a lot the work you do.
You're welcome, Juan, and thanks for your nice comments. Best of luck with your project.
I've often wondered who made the output transformers? These amps are rated at 15 watts. That's got to be a Very conservative number. I think they're capable of much more than that.
Perhaps a viewer will know the manufacturer, AL. Are there any EIA codes on them ?
Looks like a fun video series Doug. I'd be interested in your thoughts about whether a pair of these would make a good set of stereo mono amps. Looks like a good project to get into tube audio of that would work. Thanks!!
I think they would work just fine for that purpose, HS.....with a little broadening of the output frequency spectrum, which will be addressed.
o.O this circuit board looks like a nightmare 'O.o
But seeing that is easy to imagine how the sound looks like in the past.
I feel something about Rusty, he don't like to play in the heat. Oh. I have a clone of Jack, maybe I'll post a video with him.
Turning back to the amp, I'm very interested with the news😉
Rusty likes to play at night (when it's cooler)......just like us old coots (when we were young :)
People are asking $400 USD for unmodded units on feebay.. seems a bit high to me..but they are selling.
Wow, they have definitely gone way up in price. I agree that $400 is way more than the unmodified units are worth.
My Victor sound reproduction/PA amplifier is a somewhat different animal; it was made during WWII and it uses no miniature tubes. It also has a good amount of paper brick capacitors which are going to be a bit of a challenge to replace. Somewhat strangely, the speaker connects to the amplifier with a NEMA 1-15 plug.
How about a jack for an integrated swell pedal?
It does sound older and more primitive than the B&H, D20. I'm not sure what an integrated swell pedal is, so I'm afraid I can't help. If you're looking for a boost pedal, I recently posted videos showing how to build one. Good luck.
hi uncle doug, yesterday in san francisco i found one of the Filmosound amps. and me and my tech amigo r gonna do the do and get an amp outta this. the one we found is way differant. it has milatary VT107a's, a preamp tube that is the same size as a 6v6 and on the bottom it says something about Fungus Treated. We also want "A Basic guitar Amp". maybe w/ an extra gain knob. tremelo is not that important because there are these wild ass tremmy pedals out there that are great. check out the Dr. Scientist Tremmelessance ... love ur vids and your pets also :)
That sounds like an unusual find, Fatz......but any electronic device that has been "Fungus Treated" has got to be good :) I think the VT107A is equivalent, if not identical to, a 6V6. The pre-amp tube is probably
an octal pentode or duo triode, like a 6SJ7 or 6SL7....somewhere in that tube family. Best of luck with your project. Let us know how it turns out.
thanks, UD. This friday we are working on it some more and i will take a foto . i was told this was in a projector used to show propoganda films in the philipino jungle in world war 2. wow, 1941......
No wonder it was "fungus treated", Fatz....and it's even older than I am :)
I used to have a roommate that could have benefitted from fungus treatment.
Hiya Uncle Doug, very cool project here. When you were playing thru it, I didn't hear the 60hz hum but there was a lot of sizzle. What would cause that?
Thanks, Buddy. The hum is actually 120Hz and wasn't very evident on the video, but I did notice it in person. I didn't notice any sizzle, however, but I'll pay more attention in the future.
Hi Uncle Doug. There’s a strange sort of optical component called NE-2 with part number 27777 directly above the 5Y3 tube in the M1 schematic that you referenced. Do you happen to know what that component is and what it does?
It's probably a neon bulb, utilized as a current limiter to prevent the influx of a harmfully high input signal.
You're a very knowledgeable guy for sure. What guitar did you play there? That amp might be perfect for a brighter guitar like a Tele as is.
Thanks, GM. My shop guitar is a Matsumoku Vantage 695 with MMK-45 humbuckers. You're right about a telecaster brightening up a slightly muddy sound.
I have 2 of these Iv'e been using for playing guitar on gig's for over 10 years. Now I'm having problems with them getting too hot. Iv'e recapped both of them and the caps test ok. At the first tube... (V-1 5879)...202v at pin 8 and 188v at pin 7???. (I have 325v VDC at pin 4 of v4)..That's good........and no voltage at both v4 & v5 plates. Hope you could help as Los Angeles is pretty far away...and i'm hoping I can fix them...Can't wait for Part 2.
Mine was overheating due to incorrect tube biasing, CF. I suggest that you check and adjust the bias of yours. As to why you have no plate voltage on two plates, perhaps one of them is for the oscillator circuit, but I'm not sure about the other. Good luck.
My Mistake...sorry....will update you later as now my Meter is now fried.
Good luck.......
Hey UD, looks like another cool project. Would it be possible to use the extra tube socket to add spring reverb instead of tremolo to the amp?...and BTW, what is your source for schematics? I have a tweed Gibson Maestro amp with a non-working tremolo that was totally disconnected that I'd like to have working again.
Greetings, VN. Unfortunately, a proper reverb requires at least two additional tubes, a reverb-driving transformer, and a reverb tank.....which is not real feasible in this tiny chassis. To be honest, just cramming in a tremolo will be a significant challenge. I get all my schematics on line, by doing Google searches and hunting them down. Here is an example: www.drtube.com/schematics/gibson/ga-8t.gif Good luck.
hey Uncle Doug, haven't seen any vids from you this year. You doing alright?
Yes, we're all doing just fine, RL. Thanks for your concern :)
Hi again, and thanks for this very informative amp conversion video. Had a question I was wondering if you could help me with. What is your position on resistors that are out of tolerance more than what is specified on the resistor itself (silver band = +/- 10%). Over time I guess resistors drift in value. Is there a threshold where we should replace them with ones close to there specified values in the schematics? Or should we leave them as is because they contribute to the vintage tone? Thanks !
Excellent question, OB. I think it depends on where the resistor resides in the circuit. In the power supply, the values should be very close to spec, and substitution with metal film resistors will provide enhanced precision and longevity without a negative impact on tone. Likewise with screen and plate resistors. On the other hand, however, resistor tolerance in low current circuits, like the pre-amp signal pathway, is not as critical (in my opinion), and improper substitution may impact upon tone. I suggest that you experiment with resistor substitution, both in value and type, in one of your amp circuits, and see for yourself what the effects are. Best of luck.