Okay, guys, just got the amp back. Insanely awesome! Can’t tell you how much better it’s improved. Sounds absolutely amazing! Terry’s work is A+++++ . Seriously, I’ve dealt with a lot of techs in nearly three decades of playing, and he’s head and shoulders above the rest. Great guy that does great work, can’t ask for anything better.
How did it stay in such good condition? Anytime I see one so clean I assume it got stored in a closet, and forgotten for decades before getting rediscovered.
@@qua7771 would you believe I bought one last year same condition with original plastic cover ( still original tubes and aging inside no updates)? Original one owner. I'm like you ,I assume he didn't really play it . It sounds so good Im scared to use it, cause damage and not be able to replace O.E. parts.
@@l8tapex You should really have the electrolytic capacitors and the 2 prong power cord replaced at the very least if you plan to play it as you should. Just save them in a bag as they can be reinstalled should you or someone else wants to return it to original. The tubes will be fine as long as you can measure a few voltages to make sure they're to spec. Unless you want a museum piece, it's all up to you. Good luck.
I like your perspective on cap changing. Normally I hear that ceramic caps are invincible. Nothing is invincible. Very nice workmanship, as always, too.
I find it hard to add more than what has already been said in the comments. I had the same Bassman back in 1969. It was 5 years old. It had the 12 inch JBLs in it. I was a fool to have sold it. 1st wife did not understand the worth of the amp. I am going to build a single channel version with 3 band EQ. of this amp. Try to make it as clean a sound as this one. Great video Terry. Brought back some wonderful memories. Thanxz
I learned a lot from this video. Great emphasis on the wiring to the master volume. I agree it is a brilliant modification to this circuit. Thank you, D-Lab.
Excellent job, Terry, as usual. This has inspired me to finally take a look at the “yard sale find” black face Bassman that’s been in my basement for years. I always enjoy your videos, and always learn something. Thanks for sharing.
Boy that brings back memories. At the music shop (a Fender dealership) I worked at I saw a lot of these in rough shape like all the solder connections shaken to death. 100% resolder job. But when looking for upstream microphonic elements you have to have the volume controls UP not off.
Another great video, thanks! Nice to see a vintage Bassman that hasn't been hacked to death. I've restored a few vintage Fenders that were in a sorry state compared to this one. In addition to what you did, I always swap out the 2W screen resistors on the power tubes. They tend to get baked to death as the heat rises from the sockets and are often way off tolerance. Cheers.
This Amp saw the inside of a home and a Studio..it never saw a Club or any type of hall ..its been only home and studio used..another great video Terry always learn something from you
Randall, that amp is amazing. I have a few Blackface Bassmans not in as nice condition as yours, but they are a real workhorse. Anyone in your studio will drool when they see that.. Are you the original owner ? Very cool.
Terry, there's a little 1/8" plug jumper that comes with the Hakko station. Jump the power supply to the stick holder; it has a microswitch that puts the stick to sleep which makes the tip last *years* longer than it does without it. And the stick comes back up to temp as soon as you lift it from the holder.
Thank you much for the videos I have a fender bassman and a twin reverb I worked on the bassman but not the twin Now I can go back and do them both the right way Thanks again From Canada
Wow. I wish I'd had this knowledge when I rebuilt my old Wurlitzer juke box amplifier. It worked well for my bass guitar and I understood grid bias, but I could have done so much more. Thank you.
Good call changing those ceramic disk caps. They have no place in audio circuits! . I've found them to be generally microphonic. Another great vid, thanks.
Ceramic capacitors are always prone to produce some kind of noise. I replaced all of them inside my amp with polypropylene ones. I believe they sound even better than Orange Drops.
Great job Terry! You are a master with the scope! I hear those big ceramics add “character”, it appears that you don’t believe! They work great in pedals though.
Nice video, Terry! Whatever noise existed after you did the cap replacements you showed---I will GUARANDAMNTEE you that if you replace the 100K plate resistors (4 places in a Bassman--the ones that come together in the "V" shape---with 2 watt metal films---that noise will be 80% reduced. It's pretty much the same as having to replace the electrolytics under the doghouse on 40+ year old Fenders. Gotta get done, except I don't even think about the metal film plate resistors. There's nothing you can do to a Fender amp as cheap as the MF plate R's that will have anything near the effect. The hissing, popping rodent noises...those are the plate resistors. I promise. Any blackface or silverface Fender. 6 places on reverb amps. I have NEVER replaced those resistors without producing a WOW immediate and dramatic noise reduction. $3. Try it, my friend.
I'm planning on installing a master volume control on my Silverface Bassman. I can't find the model number anywhere but the closest schematic is AA371. My amp has 100K grid leak resistors so the 250K pot sold by Triad should not be used - I didn't find this out till after I bought the kit. This isn't mentioned the Triad instructions. See the rob robinette website for the "Frondelli" master volume circuit where this is discussed. I had to order another 100K pot so I can make the modification.
Hi from Dublin -- love your vids -- 2 things I find -- sometimes those carbon screen and grid resistors get baked and cracked and make noise -- also may I respectfully suggest to solder the grounds directly to the chassis -- I has seen bias failures etc die to bad continuity on those lugs bolted on the transformers -- peace
The first place to check for noise in an amp of this age, is the Filter Caps. Under the Dog House. On the bottom of the chasis. That's where you'll find the source of 60 cycle hum.
I don't work on apps I play with the two and I use all old Fender Bassman amps as well as Marshall amps from my Bass especially my frettless, I am totally about tone and I'm finding it more now with low volume by the way the Marshalls is in 1970 major you would love to work on that one its stock I loved your video
I’m surprised no one has chimed in about the master volume mod yet. I’ll explain why I added that. I should preface this by saying I’m a purist, when it comes to gear and tones, but there are realities to deal with, and Fender wasn’t perfect. I play with mostly dirt boxes that like to see the amp at the verge of breakup, what the post inverter mod allows me to do is get that at any volume, whether I’m practicing alone, with a band, or at a gig. Power tube saturation is a HUGE part of a killer recorded sound, that’s why guys like Jimmy Page used small amps for recording, so they could run it full bore. For recording, I’d run this amp as loud as I could before the preamp over saturates, but for cleaner sounds, I can definitely use the master volume to record a more pristine tone that doesn’t need that power tube saturation.
I have a Silverface Bassman that I wouldn't mind having a Master volume installed, Terry does a very good job, when He isn't swamped with repairs I may have Him do this.... cheers.... PS. Awesome soldering station Terry!
You do great work, however, it's very anti-climatic for us guitar players, not hearing a guitar through the amp. Can you get a cheap guitar and have it tuned to a chord and hang it on the wall for plugging into the amp so that we could hear a guitar through the amp? You could strum the strings and it would be a test signal.
My old room mate, amp Guru Frank Levi III didn't play guitar either, so he did just that. What non guitar playing amp techs can do now is just buy a LOOPER PEDAL WITH 9 storable loops up to 10 min each ( see below), with total max record time of 40 minutes. Records at 48 Khz, 24Mgb (far better than CD quality). Just have a visiting guitar player make a variety of loops, clean to dirty varieties. *cuvave looper* pro guitar loop pedal 9 loops total 40 minutes recording time unlimited overdubs built-in tuner function led display $50.86.$50.86 from 2 stores Features:The loop pedal with 48K/24bit sampling rate, lossless, uncompressed and professional tone quality.The total recording ... Stompbox · Looper
6:57 I just watched a "home movie" of the fender factory from 1957, the narrator spoke of how out of sorts fenders parts inventory was, so the differanct colors would verify this possibly? a must watch video on youtube
Ceramic discs are always microphoinc; it's the nature of the beast. Piezo effect, and the big disc acts as a large diaphragm. It doesn't mean it's a source of the noise we were hearing. Still great to replace with something better, but it's NOT the problem.
Just came across your channel and wondered by chance if you could comment on adding a bright switch to an Orange Brent Hinds Terror head. It’s two foot switchable channels; an amazing dirty channel that’s just right and a “natural” channel that is pretty dark for anything other than Teles or Strats. Some of suggested adding a bright input jack but that would brighten both channels... thoughts? Thanks
ok, Thts a X over amp, not flat lined AB165 at ..........ALL...............The driver n n Bias splitters say it all..Ive had several in like that great sndg amps..ive got 30 years in, store front repair...seen alot of weird stuff too :) WOO, looked CLOSER at DRIVER Thaz a REALLY REALLY rare amp, the POSITIVE FEEDBACK 220Ks form plates of power tubes to plates of driver tube was wild! THAZ where alot of noise comes from as well......Gives a bassier sound 4 sure... Fender fed back CURRENT from the speaker jack BACK to primary side of driver too, That could be a Dumblish manuever as well :)
If I recall, correct me is I'm wrong. 8:10, ceramic disc caps are essentially made like a piezo transducer, and WILL generate power when moved, pinched or tapped on.... thus the noise on that is expected... at a modest level at 16:25, the older style caps had a higher ESR than the newer stuff does/did. I know ESR can climb with age, but in reproducing vintage circuits, it seems some of our new components perform better.
I've never heard that one man. Whatever the cause, you sure don't want a cap responding to vibrations in your audio chain. They play music all their own, mostly noise. The Spragues are a good option. I normally pull ceramics out of all amps
Just as an experiment, set your scope to a high sensitivity, and put the ceramic cap on it. I'll bet it is microphonic....and generates its own voltage when bent/twisted like a piezo. Ceramic caps are usually tough as nails for other apps, but in audio, the noise is an issue, I agree on that part.
DeadKoby Ceramic caps sound awful, regardless. To my ears PIO always have more character. Ceramics are frequently extremely sterile in a best case, and cold and thin in a worst case. Film are reliable, long lasting, and impart a slightly warmer feel. Film and PIO sound nearly identical, but ceramic bring nothing of value to the party.
Cleaner? No thx Terry I want the sound of every control dimed -red hot crunch and dirt - but at a much lower overall volume. The the way I'd run that master volume for recording would be all channel controls on 10 - but the master at 1-2. The high gain noise...that's why they make noise gates LOL. GREAT work as always Terry you are an artist sir !
Tioga Fretworks I run both channels jumped a la Marshall plexi style. This thing sounds great with both channels dimed. The master above 3 is insanely loud.
If you have to replace resistors in these amps would the metalize resistors work better I like that you use orange drops caps,pricey but nice.you really do great work
Even brand new ceramic caps are suseptible to physical manipulation and produce voltage by themself if manipulated. If im not mistaken. Were those actually bad?
Excellent video! I have two of these heads and the work on the first one is almost done so it was good to see this video. Did you check the filter caps at some point or know they had been replaced with the other electrolytic’s? Really enjoy your videos, always learn!
Change the 4 qty 100K preamp plate resistors with 2 watt metal films. The ones arranged in the "V" shape. Massive difference in hiss-pop noise, not subtle at all.
Great video! Can you apply this master volume mod to an Ampeg SVT VR as well? So you can dial in a "dirtier" tone with preamp volume knob but control the overall output volume with a master volume without sacrificing any of the tone?
my bassman one power tube out of 4 gets hotter then others. all voltages are correct. only missmatch is after PI 318V and 306V. OT is also warm on idle. Sockets look fine. What could it be or it's normal? Thanx
Great Video! I love the thorough ones. It does make me sad tho because I owned a 67 that was just as clean... in fact I think I traded it to a guy in Indiana... Crap... lol...
SEE *Trainwreck Pages - Rob Robinette's* and scroll to TYPE 1 MASTER VOLUME. This will be the one D-Lab is doing. EVERY BRITISH 50-200 WATT HARD ROCK/METAL AMP (Marshall, Hiwatt, Sound City, Orange, Laney) [not sure about CLASS-A VOX amps], as well as U.S. amps- Ampeg, Mesa Boogie, Kustom, Peavey,Soldano, Trainwreck(US?), etc....all of these amps sound great with this Master volume.
@@d-labelectronics Clean channel works but breaks up randomly. The dirty channel is noisy and sounds like crap. When turning the reverb on ..the amp makes a loud squeel and hiss. I put new tubes in but to no avail. The sound will just break up and get quiet.
Can you recommend a decent, new oscilloscope, easily available via amazon or similar? I used to work on tube amps a long time ago, but starting to get back into it, and just found that my old scope is toast. I was looking at the Hantek DSO2C10, but not sure if that's overkill or? I have a lot to re-learn, but your videos are helping a ton (and inspiring). Thank you!
Terry, request: For a simple mod to any amp. Add two output jacks to the back of the amp. 1: XLR male mic level OUTPUT jack to go to low imp input on the mixer. 2: RCA or 1/4" Line level OUTPUT jack to go to line input on the mixer or recorder. They could be tapped into the preamp section, using an inp matching transformer. I see many bands using mics in front of small amp speakers. Direct hookup avoids many problems. But I've yet to see any amp with XLR low imp output to mixer mic level input. Could be a D Lab exclusive feature! Don
umajunkcollector Bass amps often have that, and is a nice touch, but for a guitar (primarily) amp, they usually don’t sound great without some power tube soak going on, especially using pedals and whatnot. In lieu of miking a speaker, tapping the DI post output sounds way better, either via an attenuator, or something like the Weber Z Matcher, where you can access all stages of saturation at a line level.
Soooo, its not only that tube sound, i.e. mic the sound of the crappy little over driven speaker too? Um thunkin get away from that speaker, bypass it, by going direct. Yes, some MODERN SOLID STATE AMPS have outputs. But few old TUBE AMPS did. Where to tap in for audio output to get that tube sound? I agree in a way, at the speaker stage of the amp, where as you also get overdrive, vol and EQ-tone from the amp's settings. Some resistors and transformer might do the trick to an XLR and line out jack. I'd like to see what Terry would come up with ?
umajunkcollector Oh, I’m sure someone could devise a way to do it, but every amp DI, aside from bass amps, sounds terrible to me. Some have speaker emulators, but they don’t sound great either. Celestion makes some killer IRs, if someone could implement that, that might work. The Weber Z Matcher has a DI using transformers and whatnot, but it’s way too big to build into an amp.
But isn't the 100$+ Weber for matching amp speaker output to 2-16 ohms speakers? Mixer's are much different, low z mic, and hi z guitar pickups, and high z line in, far from 8 ohms, more like 200-20k-200k. Maybe the overload is why a direct connection, from speaker terminals to mixer sounds bad. But then again part of mic in front of speaker, gets that speaker sound too, besides the tube sound.
A simple 2$ 500k pot could attenuate the match from speaker to mixer? OK Terry, wassupwitdat? Ham radio guys often use a "matchbox" or antenna tuner to match the transmitter output to antenna, or at least a BalUn transformer. The matchbox uses a transformer and capacitor to match RF z. Audio is much lower freqs, and speakers are not like antennas. Speakers radiate air waves, antennas radiate RF energy. But matching impedence is the goal.
What is your going rate to work on an amp. I just got a 68 Bassman. It has a little hissing noise and it seems like when your playing the guitar it goes a little lower sometimes. Usually when you first turn it on. Let me know thank you sir. Love the videos so interesting.
So, is it possible to explain the dummy load, as well as how you're using the scope? Or, if you've got vids already covering that, can you point me to it/them? 🤓
A master volume is not to limit noise , it's to get preamp breakup at lower volume, ( think Mesa Boogie),why not install a three prong cord and use the obsolete ground reversing switch hole for the master volume pot?
Terry, I have worked on many of these and that one is pristine.If that had the Drip Edge it would really be a relic. I had that crackle problem Many times, and it was the disc cap as well. One had a hairline fracture. After replacing the amp was quiet as can be. I use the same soldering station - its awesome. I also noticed you added an electrolytic cap on the center of the Bias Pot to ground. Was that to eliminate noise or to ensure the negative bias was not affected ? I did notice the master volume slightly changed your negative bias.. very slightly. Nicely done Terry, as usual !!! P.S. I notice you are not using the Hakko Lockout Key on your unit - Be careful.... Dick from the Internet may come and change the temps on you... LOL Seriously, really quality video again.. well done - THANKS RON
Ron C Drip edges are sharp, I’ll give ya that, but the BF are worth about 25-35% more. :) And buying a silver face is a gamble, because that’s when CBS went a bit wild with things, using about 10 different circuits in a few years, and if the tube arrangement was the same, they stuck whatever label inside they had in stock, not necessarily what it is. So, if you want an AB165 silver face, the only way to be certain is open her up and take a look. Some SF circuits, generally post 1970, are widely considered awful, but I’ve typically liked the ones I’ve heard. A lot of BF guys like the original AA864, but side by side with an AB165, the 165 blows the doors off.
I have 2 SF 50's that I restored. Neither was rusty and both are in tip top shape now. Biggest difference is the grill cloth which I had to replace, but aside for that its mint.
My rarely used Fender 59 Bassman 4-10' combo amp has very loud Hum and slight popping sound , it sounds exactly like this but way louder , this is like normal tube amp hum. it did have 2 new power tubes and one preamp tube replaced. I took it to this local amp repair guy he hook it up outside you can barely heart it and he goes I don't hear anything wrong here, he ask me if I have dim light switch , bad grounding etc yea I am familiar with that, but I have other tube amps that does not have this excessive loud hum sound maybe after you biased it the humming sound comes on, so he did not want to check the capacitors voltage make sure all working correctly, I already email you about this issue but you are full of clients at this moment. I think i might sell the amp , I can't stand amp with the loud humming sound going on. I bought a brand new Mesa Boogie amp that had the same problem, loud hum took it back to the store and got my money refunded. So I have no idea what's causing the amp to Hum so loud
hello mr I hope you were well I wanted to ask you something that happened to me with bassman 59 I did the master volume and it looks good but now I feel some background noise I noticed that you used a master volume and I could notice that you put a filter in the bia potentiometer Could you tell me if that could remove the background noise that I comment on the master volume?
I do disagree a little with the statement that a post phase inverter master volume doesn’t affect tone. When you look at technical sheets of pentode/tetrode power tubes - they display asymmetric compression not to mention clipping that single ended preamp tubes can’t accomplish, save perhaps an ef86 pentode preamp tube.
I had a master volume added to my 65 Showman thinking I might be able to use it at lower volumes with at least a bit of breakup, turned out to be a waste of time, still no breakup even with the master low and the main vol. high...
Brother D-Lab, pls try a master X line X the grids of the driver pin 2 n 7 :) U mit be surprised....Even QUIETER than the Dual....n MUCH simpler.................:)
Okay, guys, just got the amp back. Insanely awesome! Can’t tell you how much better it’s improved. Sounds absolutely amazing! Terry’s work is A+++++ . Seriously, I’ve dealt with a lot of techs in nearly three decades of playing, and he’s head and shoulders above the rest. Great guy that does great work, can’t ask for anything better.
How did it stay in such good condition? Anytime I see one so clean I assume it got stored in a closet, and forgotten for decades before getting rediscovered.
@@qua7771 would you believe I bought one last year same condition with original plastic cover ( still original tubes and aging inside no updates)? Original one owner. I'm like you ,I assume he didn't really play it . It sounds so good Im scared to use it, cause damage and not be able to replace O.E. parts.
@@l8tapex You should really have the electrolytic capacitors and the 2 prong power cord replaced at the very least if you plan to play it as you should. Just save them in a bag as they can be reinstalled should you or someone else wants to return it to original. The tubes will be fine as long as you can measure a few voltages to make sure they're to spec. Unless you want a museum piece, it's all up to you. Good luck.
I don't even know why I watch this channel. I don't even work on electronics, but I watch this shit everyday.
I like your perspective on cap changing. Normally I hear that ceramic caps are invincible. Nothing is invincible. Very nice workmanship, as always, too.
I find it hard to add more than what has already been said in the comments. I had the same Bassman back in 1969. It was 5 years old. It had the 12 inch JBLs in it. I was a fool to have sold it. 1st wife did not understand the worth of the amp. I am going to build a single channel version with 3 band EQ. of this amp. Try to make it as clean a sound as this one. Great video Terry. Brought back some wonderful memories. Thanxz
Thank you very much Mr. Terry for this beautiful class, these amplifiers are excellent and deserve this love. 73 by PY2SNN Sebastian
You da' MAN, Terry! Now the sound matches the incredible looks of this excellent Bassman.
I learned a lot from this video. Great emphasis on the wiring to the master volume. I agree it is a brilliant modification to this circuit. Thank you, D-Lab.
Excellent job, Terry, as usual. This has inspired me to finally take a look at the “yard sale find” black face Bassman that’s been in my basement for years. I always enjoy your videos, and always learn something. Thanks for sharing.
Cool deal man, Thats a great find. Let me know if I can be of assistance
Yàà
Some "yard sale" LOL - still I shouldn't complain - I found a pretty complete Vox AC30 chassis in the trash once :)
Boy that brings back memories. At the music shop (a Fender dealership) I worked at I saw a lot of these in rough shape like all the solder connections shaken to death. 100% resolder job. But when looking for upstream microphonic elements you have to have the volume controls UP not off.
Another great video, thanks! Nice to see a vintage Bassman that hasn't been hacked to death. I've restored a few vintage Fenders that were in a sorry state compared to this one. In addition to what you did, I always swap out the 2W screen resistors on the power tubes. They tend to get baked to death as the heat rises from the sockets and are often way off tolerance. Cheers.
Actually, just watched another video where you do address the screen resistor issue. Good on ya! I'm new to your channel and still catching up.
This Amp saw the inside of a home and a Studio..it never saw a Club or any type of hall ..its been only home and studio used..another great video Terry always learn something from you
@Mydickishard - It could have been used on gigs and well cared for including a road case
Excellent video. You know how much we love Fender Amps. Thanks Terry.
I’ve watched probably 500 of his videos, but when it’s your amp, man, that’s really cool.
Yes Sir, This was a great project, more to do, but coming along nicely.
Randall, that amp is amazing. I have a few Blackface Bassmans not in as nice condition as yours, but they are a real workhorse. Anyone in your studio will drool when they see that.. Are you the original owner ? Very cool.
Ron C No, I’m not the original owner. The amp is 11 years older than me. Haha.
Very clean amp. Also nice troubleshooting and modification. Excellent work as always Terry.
Terry, there's a little 1/8" plug jumper that comes with the Hakko station. Jump the power supply to the stick holder; it has a microswitch that puts the stick to sleep which makes the tip last *years* longer than it does without it. And the stick comes back up to temp as soon as you lift it from the holder.
Thank you much for the videos
I have a fender bassman and a twin reverb
I worked on the bassman but not the twin
Now I can go back and do them both the right way
Thanks again
From Canada
Wow. I wish I'd had this knowledge when I rebuilt my old Wurlitzer juke box amplifier. It worked well for my bass guitar and I understood grid bias, but I could have done so much more. Thank you.
If anyone is curious, that’s my amp, and I sold those two Ajax coupling caps for $50. People will buy anything vintage.
hahaha that is amazing
I just did an aa864 conversion to a 66. I couldn’t get those blue moldies out fast enough.
@@luthiervandros All this time I thought just the yellow caps were bad.
@@markwhitney5667 oh I just meant the bad ones lol
Whow! I got a stash of like two dozen of em...
Terry I just fnished my first MV on a Bassman AA864 That I scratch built. Man I love it! This thing ROCKS!
Thanks for the awesome instructions!
Good call changing those ceramic disk caps. They have no place in audio circuits! . I've found them to be generally microphonic. Another great vid, thanks.
...THAT'S NEWS TO ME-!!!
I loved seeing that amp. but, more so.. I enjoyed learning a few new things. Thanks Terry.
Terry, great video, systematic and thorough trobleshooting
That's one damn clean amplifier! Great video, Terry!
Ceramic capacitors are always prone to produce some kind of noise. I replaced all of them inside my amp with polypropylene ones. I believe they sound even better than Orange Drops.
The color of the caps mean nothing.
Hey D-Lab thanks for another video!
Great job Terry! You are a master with the scope! I hear those big ceramics add “character”, it appears that you don’t believe! They work great in pedals though.
Nice video, Terry! Whatever noise existed after you did the cap replacements you showed---I will GUARANDAMNTEE you that if you replace the 100K plate resistors (4 places in a Bassman--the ones that come together in the "V" shape---with 2 watt metal films---that noise will be 80% reduced. It's pretty much the same as having to replace the electrolytics under the doghouse on 40+ year old Fenders. Gotta get done, except I don't even think about the metal film plate resistors. There's nothing you can do to a Fender amp as cheap as the MF plate R's that will have anything near the effect. The hissing, popping rodent noises...those are the plate resistors. I promise. Any blackface or silverface Fender. 6 places on reverb amps. I have NEVER replaced those resistors without producing a WOW immediate and dramatic noise reduction. $3. Try it, my friend.
Sorry for the dumb question, are you talking about the preamp and PI plates resistors?
Great video Terry as always, and I learned a lot. Such a lovely clean amp, I really wanted to see the filter caps under the dog house cover too !
I have a blackstar with a master volume which allows you to run your tubes wide open and still have playable volume levels.
Thanks, Terry! Looking forward to rocking this out!
Beauty of an amp
I agree Terry those grid coupling caps are known to go bad even in old radios it's just not worth the risk
I'm planning on installing a master volume control on my Silverface Bassman. I can't find the model number anywhere but the closest schematic is AA371. My amp has 100K grid leak resistors so the 250K pot sold by Triad should not be used - I didn't find this out till after I bought the kit. This isn't mentioned the Triad instructions. See the rob robinette website for the "Frondelli" master volume circuit where this is discussed. I had to order another 100K pot so I can make the modification.
Excellent work right through.
Hi from Dublin -- love your vids -- 2 things I find -- sometimes those carbon screen and grid resistors get baked and cracked and make noise -- also may I respectfully suggest to solder the grounds directly to the chassis -- I has seen bias failures etc die to bad continuity on those lugs bolted on the transformers -- peace
Cool video, appreciate the detailed instructions and clear explanations of what is being done. You have a new subscriber! Thanks!
I suggest using an insulated sleeve when mounting the master volume pot. This might prevent shorting the tube bias to ground if the pots fail.
Nice one Terry!
Good one Terry! I think I'm ready for a soldering station upgrade, too. Merry Christmas to you and your family!
The first place to check for noise in an amp of this age, is the Filter Caps. Under the Dog House. On the bottom of the chasis. That's where you'll find the source of 60 cycle hum.
The fact that he didn't even address these makes me think that they were already recently replaced...
@D-lab Electronics, can you do a detail video on your setup with the dummy load and the output to your Scope?
Terry! @D-lab Electronics I just bought a Tektronix scope and I NEED you to do a video on the above!!!
I don't work on apps I play with the two and I use all old Fender Bassman amps as well as Marshall amps from my Bass especially my frettless, I am totally about tone and I'm finding it more now with low volume by the way the Marshalls is in 1970 major you would love to work on that one its stock I loved your video
Terry really enjoy your videos. Just wish you could do one on a Guild Thunderbird. I am having trouble with mine. Thanks
Great looking amp
I’m surprised no one has chimed in about the master volume mod yet. I’ll explain why I added that. I should preface this by saying I’m a purist, when it comes to gear and tones, but there are realities to deal with, and Fender wasn’t perfect. I play with mostly dirt boxes that like to see the amp at the verge of breakup, what the post inverter mod allows me to do is get that at any volume, whether I’m practicing alone, with a band, or at a gig. Power tube saturation is a HUGE part of a killer recorded sound, that’s why guys like Jimmy Page used small amps for recording, so they could run it full bore. For recording, I’d run this amp as loud as I could before the preamp over saturates, but for cleaner sounds, I can definitely use the master volume to record a more pristine tone that doesn’t need that power tube saturation.
I have a Silverface Bassman that I wouldn't mind having a Master volume installed, Terry does a very good job, when He isn't swamped with repairs I may have Him do this.... cheers.... PS. Awesome soldering station Terry!
Can do man, How's retirement going?
It really hasn't set in yet,but I am relaxed, chilling in AC ,I can drop the Bassman off whenever it's convenient for you.
Maybe next weekend, no AC here at D-lab ; (
You do great work, however, it's very anti-climatic for us guitar players, not hearing a guitar through the amp. Can you get a cheap guitar and have it tuned to a chord and hang it on the wall for plugging into the amp so that we could hear a guitar through the amp? You could strum the strings and it would be a test signal.
My old room mate, amp Guru Frank Levi III didn't play guitar either, so he did just that. What non guitar playing amp techs can do now is just buy a LOOPER PEDAL WITH 9 storable loops up to 10 min each ( see below), with total max record time of 40 minutes. Records at 48 Khz, 24Mgb (far better than CD quality). Just have a visiting guitar player make a variety of loops, clean to dirty varieties.
*cuvave looper* pro guitar loop pedal 9 loops total 40 minutes recording time unlimited overdubs built-in tuner function led display
$50.86.$50.86 from 2 stores
Features:The loop pedal with 48K/24bit sampling rate, lossless, uncompressed and professional tone quality.The total recording ...
Stompbox · Looper
6:57 I just watched a "home movie" of the fender factory from 1957, the narrator spoke of how out of sorts fenders parts inventory was, so the differanct colors would verify this possibly? a must watch video on youtube
It would have been good to have heard the amp after the modifications to see the difference.
Trust me, it’s awesome. Terry did a fantastic job on it.
Ceramic discs are always microphoinc; it's the nature of the beast. Piezo effect, and the big disc acts as a large diaphragm. It doesn't mean it's a source of the noise we were hearing. Still great to replace with something better, but it's NOT the problem.
Just came across your channel and wondered by chance if you could comment on adding a bright switch to an Orange Brent Hinds Terror head. It’s two foot switchable channels; an amazing dirty channel that’s just right and a “natural” channel that is pretty dark for anything other than Teles or Strats. Some of suggested adding a bright input jack but that would brighten both channels... thoughts? Thanks
ok, Thts a X over amp, not flat lined AB165 at ..........ALL...............The driver n n Bias splitters say it all..Ive had several in like that great sndg amps..ive got 30 years in, store front repair...seen alot of weird stuff too :) WOO, looked CLOSER at DRIVER Thaz a REALLY REALLY rare amp, the POSITIVE FEEDBACK 220Ks form plates of power tubes to plates of driver tube was wild! THAZ where alot of noise comes from as well......Gives a bassier sound 4 sure... Fender fed back CURRENT from the speaker jack BACK to primary side of driver too, That could be a Dumblish manuever as well :)
If I recall, correct me is I'm wrong. 8:10, ceramic disc caps are essentially made like a piezo transducer, and WILL generate power when moved, pinched or tapped on.... thus the noise on that is expected... at a modest level
at 16:25, the older style caps had a higher ESR than the newer stuff does/did. I know ESR can climb with age, but in reproducing vintage circuits, it seems some of our new components perform better.
I've never heard that one man. Whatever the cause, you sure don't want a cap responding to vibrations in your audio chain. They play music all their own, mostly noise. The Spragues are a good option. I normally pull ceramics out of all amps
Just as an experiment, set your scope to a high sensitivity, and put the ceramic cap on it. I'll bet it is microphonic....and generates its own voltage when bent/twisted like a piezo. Ceramic caps are usually tough as nails for other apps, but in audio, the noise is an issue, I agree on that part.
DeadKoby Ceramic caps sound awful, regardless. To my ears PIO always have more character. Ceramics are frequently extremely sterile in a best case, and cold and thin in a worst case. Film are reliable, long lasting, and impart a slightly warmer feel. Film and PIO sound nearly identical, but ceramic bring nothing of value to the party.
However ceramic's durability in function circuits (not the audio path) is a plus, so they have their usages.
Cleaner? No thx Terry I want the sound of every control dimed -red hot crunch and dirt - but at a much lower overall volume. The the way I'd run that master volume for recording would be all channel controls on 10 - but the master at 1-2. The high gain noise...that's why they make noise gates LOL. GREAT work as always Terry you are an artist sir !
Tioga Fretworks I run both channels jumped a la Marshall plexi style. This thing sounds great with both channels dimed. The master above 3 is insanely loud.
Gud job mister. In the end of the video , add one cap. in the Bias pot. Its for stabilicing the negative tension?
Thanks for your great chanel.
If you have to replace resistors in these amps would the metalize resistors work better I like that you use orange drops caps,pricey but nice.you really do great work
Even brand new ceramic caps are suseptible to physical manipulation and produce voltage by themself if manipulated. If im not mistaken. Were those actually bad?
Excellent video! I have two of these heads and the work on the first one is almost done so it was good to see this video. Did you check the filter caps at some point or know they had been replaced with the other electrolytic’s? Really enjoy your videos, always learn!
Yes, owner showed me pics of the new installed Mallorys
D-lab Electronics. It’s a treat to be able to see these videos and learn. Thank you for sharing your knowledge. Happy Memorial Day.
Roger that man, 12 yrs USAF here
D-lab Electronics thank you for your service!
Change the 4 qty 100K preamp plate resistors with 2 watt metal films. The ones arranged in the "V" shape. Massive difference in hiss-pop noise, not subtle at all.
Have you ever checked out the ken Fisher master volume control. It's much simpler and works just as well !!!!!!
Great video! Can you apply this master volume mod to an Ampeg SVT VR as well? So you can dial in a "dirtier" tone with preamp volume knob but control the overall output volume with a master volume without sacrificing any of the tone?
my bassman one power tube out of 4 gets hotter then others. all voltages are correct. only missmatch is after PI 318V and 306V. OT is also warm on idle. Sockets look fine. What could it be or it's normal? Thanx
I need to see it on a schematic to understand what it's doing.. are we just shunting some signal from output tube grids to ground with the pot?
Great Video! I love the thorough ones. It does make me sad tho because I owned a 67 that was just as clean... in fact I think I traded it to a guy in Indiana... Crap... lol...
fantastic video, thumbs up from me!
SEE *Trainwreck Pages - Rob Robinette's* and scroll to TYPE 1 MASTER VOLUME. This will be the one D-Lab is doing. EVERY BRITISH 50-200 WATT HARD ROCK/METAL AMP (Marshall, Hiwatt, Sound City, Orange, Laney) [not sure about CLASS-A VOX amps], as well as U.S. amps- Ampeg, Mesa Boogie, Kustom, Peavey,Soldano, Trainwreck(US?), etc....all of these amps sound great with this Master volume.
I love your videos. Wish I could have you fix my fender twin
Hi Dan, What is the problem your having with the Twin?
@@d-labelectronics Clean channel works but breaks up randomly. The dirty channel is noisy and sounds like crap. When turning the reverb on ..the amp makes a loud squeel and hiss. I put new tubes in but to no avail. The sound will just break up and get quiet.
Can you recommend a decent, new oscilloscope, easily available via amazon or similar? I used to work on tube amps a long time ago, but starting to get back into it, and just found that my old scope is toast. I was looking at the Hantek DSO2C10, but not sure if that's overkill or?
I have a lot to re-learn, but your videos are helping a ton (and inspiring). Thank you!
Terry Great video. One question-should you terminate the AC lines for the deleted two pronged plug before powering it up ? Thanks !
Terry, request:
For a simple mod to any amp.
Add two output jacks to the back of the amp.
1: XLR male mic level OUTPUT jack to go to low imp input on the mixer.
2: RCA or 1/4" Line level OUTPUT jack to go to line input on the mixer or recorder.
They could be tapped into the preamp section, using an inp matching transformer.
I see many bands using mics in front of small amp speakers. Direct hookup avoids many problems. But I've yet to see any amp with XLR low imp output to mixer mic level input.
Could be a D Lab exclusive feature!
Don
umajunkcollector Bass amps often have that, and is a nice touch, but for a guitar (primarily) amp, they usually don’t sound great without some power tube soak going on, especially using pedals and whatnot. In lieu of miking a speaker, tapping the DI post output sounds way better, either via an attenuator, or something like the Weber Z Matcher, where you can access all stages of saturation at a line level.
Soooo, its not only that tube sound, i.e. mic the sound of the crappy little over driven speaker too? Um thunkin get away from that speaker, bypass it, by going direct.
Yes, some MODERN SOLID STATE AMPS have outputs. But few old TUBE AMPS did.
Where to tap in for audio output to get that tube sound? I agree in a way, at the speaker stage of the amp, where as you also get overdrive, vol and EQ-tone from the amp's settings. Some resistors and transformer might do the trick to an XLR and line out jack.
I'd like to see what Terry would come up with ?
umajunkcollector Oh, I’m sure someone could devise a way to do it, but every amp DI, aside from bass amps, sounds terrible to me. Some have speaker emulators, but they don’t sound great either. Celestion makes some killer IRs, if someone could implement that, that might work. The Weber Z Matcher has a DI using transformers and whatnot, but it’s way too big to build into an amp.
But isn't the 100$+ Weber for matching amp speaker output to 2-16 ohms speakers? Mixer's are much different, low z mic, and hi z guitar pickups, and high z line in, far from 8 ohms, more like 200-20k-200k. Maybe the overload is why a direct connection, from speaker terminals to mixer sounds bad. But then again part of mic in front of speaker, gets that speaker sound too, besides the tube sound.
A simple 2$ 500k pot could attenuate the match from speaker to mixer? OK Terry, wassupwitdat?
Ham radio guys often use a "matchbox" or antenna tuner to match the transmitter output to antenna, or at least a BalUn transformer. The matchbox uses a transformer and capacitor to match RF z. Audio is much lower freqs, and speakers are not like antennas. Speakers radiate air waves, antennas radiate RF energy. But matching impedence is the goal.
thx terry :) have a great day!
What is your going rate to work on an amp. I just got a 68 Bassman. It has a little hissing noise and it seems like when your playing the guitar it goes a little lower sometimes. Usually when you first turn it on. Let me know thank you sir. Love the videos so interesting.
What is that thing sticking out of the back of the amp? Dummy load? Is that home made? How did you make it?
My favorite scope!
Also.. Hako 936... Best soldering station.. Still use it til this day (4-18-2020)
I like that dummy load you have made, looks like you attached it to a jack, what's the spec?
How's about a dpdt relayed to bypass the msster and simultaneously switch an extra gain stage in/out.
Excellent video
Really great video
Do you know of a good replacement .001uf 1kv ceramic cap? I can’t find a orange drop with 1kv.
Nice video, like always. Couls you do a video of how to Black face a Bassman 100 silver face ? It would be awesome
I’ve got a vintage 100 watt Carvin I’d like you to fix
Great video! Where are you located??? I want to drop off my early 70's Bassman 50.
I need to replace my scope. What would you recommend for repairing amplifiers such as what you work on? Thanks.
Hey Terry. What's the blue cap at the bias pot in the final picture?
So, is it possible to explain the dummy load, as well as how you're using the scope? Or, if you've got vids already covering that, can you point me to it/them? 🤓
Found the Dummy head video so there's that
Where did you get the lighted magnifier
Good job!
Great info Thanks
A master volume is not to limit noise , it's to get preamp breakup at lower volume, ( think Mesa Boogie),why not install a three prong cord and use the obsolete ground reversing switch hole for the master volume pot?
My amplifier is a star force USA amp from the 90s sometimes the gain doesn’t turn on
Terry, I have worked on many of these and that one is pristine.If that had the Drip Edge it would really be a relic. I had that crackle problem Many times, and it was the disc cap as well. One had a hairline fracture. After replacing the amp was quiet as can be. I use the same soldering station - its awesome. I also noticed you added an electrolytic cap on the center of the Bias Pot to ground. Was that to eliminate noise or to ensure the negative bias was not affected ? I did notice the master volume slightly changed your negative bias.. very slightly. Nicely done Terry, as usual !!! P.S. I notice you are not using the Hakko Lockout Key on your unit - Be careful.... Dick from the Internet may come and change the temps on you... LOL Seriously, really quality video again.. well done - THANKS RON
Ron C Drip edges are sharp, I’ll give ya that, but the BF are worth about 25-35% more. :) And buying a silver face is a gamble, because that’s when CBS went a bit wild with things, using about 10 different circuits in a few years, and if the tube arrangement was the same, they stuck whatever label inside they had in stock, not necessarily what it is. So, if you want an AB165 silver face, the only way to be certain is open her up and take a look. Some SF circuits, generally post 1970, are widely considered awful, but I’ve typically liked the ones I’ve heard. A lot of BF guys like the original AA864, but side by side with an AB165, the 165 blows the doors off.
I agree with you Randall. BF are the ticket.
Ron C It’s rare to find a SF that isn’t rusty as hell either. Personally, I do prefer the drip edge look.
I have 2 SF 50's that I restored. Neither was rusty and both are in tip top shape now. Biggest difference is the grill cloth which I had to replace, but aside for that its mint.
Ron C It's not an electro, it's a law-faking resistor, to make the linear pot behave like a log pot.
My rarely used Fender 59 Bassman 4-10' combo amp has very loud Hum and slight popping sound , it sounds exactly like this but way louder , this is like normal tube amp hum. it did have 2 new power tubes and one preamp tube replaced. I took it to this local amp repair guy he hook it up outside you can barely heart it and he goes I don't hear anything wrong here, he ask me if I have dim light switch , bad grounding etc yea I am familiar with that, but I have other tube amps that does not have this excessive loud hum sound maybe after you biased it the humming sound comes on, so he did not want to check the capacitors voltage make sure all working correctly, I already email you about this issue but you are full of clients at this moment. I think i might sell the amp , I can't stand amp with the loud humming sound going on. I bought a brand new Mesa Boogie amp that had the same problem, loud hum took it back to the store and got my money refunded. So I have no idea what's causing the amp to Hum so loud
Was something getting microphonic at 1:30-1:50ish. Your audio was a little reverby.
Or was that a different mic?
Hello, Yes, that was a boom mic. I wanted to capture the hiss+ birdies without background noise in the shop. Good catch
hello mr I hope you were well I wanted to ask you something that happened to me with bassman 59 I did the master volume and it looks good but now I feel some background noise I noticed that you used a master volume and I could notice that you put a filter in the bia potentiometer Could you tell me if that could remove the background noise that I comment on the master volume?
I do disagree a little with the statement that a post phase inverter master volume doesn’t affect tone. When you look at technical sheets of pentode/tetrode power tubes - they display asymmetric compression not to mention clipping that single ended preamp tubes can’t accomplish, save perhaps an ef86 pentode preamp tube.
Would that cap issue show up with a speaker plugged in without the scope?
how about a schematic for the master volume.
I had a master volume added to my 65 Showman thinking I might be able to use it at lower volumes with at least a bit of breakup, turned out to be a waste of time, still no breakup even with the master low and the main vol. high...
Wait... how does it sound now???
would like this mater volume mod done on my carvin nomad amp
Kendricks amps charged me $1200 and kept my 63 Bandmaster for a year,shotguned all my caps...,all that was wrong was a old ground wire
Brother D-Lab, pls try a master X line X the grids of the driver pin 2 n 7 :) U mit be surprised....Even QUIETER than the Dual....n MUCH simpler.................:)
What is the name of the song and the artist you used in the intro for this video?