1978 Fender 135W Twin Reverb Kicks Ass.....in more ways than one
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- Опубліковано 18 жов 2024
- In this video we undertake the extremely difficult repair of a 1978 Fender Silverface Twin Reverb with both Push-Pull Boost and Master Volume Control. The repairs are made even more complicated due to extensive prior "repairs" (by individuals unknown). In effect, every single wire, connection, and component has to be double-checked, and many errors are found. In addition the customer requested that the Boost and Master Volume be completely removed from the circuit, which I did, and then replaced the original pot & switch with a variable NFB control. This process is carefully explained for viewers who would like to rid their circuits of this tone-sucking mess. All repairs appear successful until the amp receives its final audio check......and almost passes, before demonstrating problems in the Vibrato/Tremolo circuit, which will be addressed in a future video (unless I retire to avoid it).
There are several visits from Jack, KC, and a particularly menacing old 1930 Ford hot rod.....so get ready for a real adventure in the type of amp repair challenge that can drive strong men to alcohol......and thoughts of suicide :)
If you enjoy advertising-free, in-depth yet easily-undertood videos like this one, then please subscribe to our channel and consider becoming a Patreon patron at / uncledougsvintageamps or making a PayPal donation to: dldcam@aol.com. Thanks so much for your interest and support :)
I started checking my UA-cam subscriptions for this video the moment I mailed it in. Thanks for going to battle!
Watched the video - outstanding work UD! To answer a few questions: I know what you're thinking and yes, this amp was not worth repairing. The fact that UD fixed it not only demonstrates his remarkable skill, exceptional teaching gift, and sense of humor, but also showcases his willingness to help. I asked him to proceed as a cautionary tale for his viewers. He spared my pride a lot in the video. I'm a cheapskate and the amp was an eBay purchase that seemed like a deal. I thought I could save a few dollars by buying one that was "fixed", but needed "finished" with new tubes and the poorly recovered cabinet rectified. It came with some old parts the proved it was fixed. It arrived and powered on with a hum, but it scared me so bad, I locked it in a closet for a while. Eventually I bought new tubes and an unmolested original cabinet. Of course the new tubes didn't help much so I bought what I thought was a new hum balance pot to fix the "minor hum problem" that remained. It became clear that the amp was very sick. So much so that when I turned the volume knob up the shower faucet came on. So I bought a replacement for the missing foot switch and then I bought casters for the cabinet. This also didn't fix the amp. With what I spent on parts etc, I could have bought a nice known-good non-MV Twin.
I may be cheap, but I'm not a quitter, so I gave up and mailed it to UD because at some point knowing what was wrong with the amp became just as valuable to me as the actual amp. Furthermore, I didn't want a MV Twin Reverb, which is why I bought one in the first place… Like many, many others, I wanted it removed so I asked Internet. Instead of answering that question, Internet answered another, different question - "set it to 10 and ignore it". UD answered the actual question and documented it.
To my fellow cheapskates: don't be like me. Wait for the right amp. Contrary to what your brain may tell you, it's actually cheaper to spend $1000 one time than to spend $200 10 times over the course of two years.
Thanks for your very honest and illuminating commentary, K. This amp is indeed an excellent lesson in the British term "false economy", in which an apparent bargain can often turn into a bottomless pit of expense and frustration. In this case, it WILL work.....but as we both discovered, the effort and expense are far in excess of what should normally be required to resurrect a vintage circuit.
I have this amp too that I am about to go to battle on! I haven't even started the video yet and I am super excited.
I hope it lives up to your expectations, Mr. C.
I forgot to mention in my comment above that just the MV removal demonstration is worth some financial support for UD. For those of you wondering, it takes hours of his time corresponding, researching, repairing, recording and editing to produce these videos. And he gives away this effort and knowledge for free. Please consider showing your appreciation.
Everyone that has owned or fixed a number of amps for a long enough time gets one just like this. Twin chassis, complete, $200 OBO.
I'm just a guitar player but now I know what my amp tech is going through when I bring in my Fender for service. He is worth every dollar I pay him. Can I get an Amen.
Yes, you can :)
Dear Uncle Doug: You're not fooling me. You loved every minute you hated it. So did we. Thanks for the hard work.
I guess you got me there, Rowdy. There is no gain without some pain :)
Uncle Doug If my bowels fall out of a gaping wound in my abdomen, can I then count that as an immense gain?
@@UncleDoug Ooh guitar amplification puns. I have to steal that.
Well done , resurrection can be time consuming, and yes…. Difficult. It is a good feeling after it is over. The cringe you must have felt when you saw the extent….. and then the noise at the end as it gave up….. 😊 I feel your pain.
I really enjoyed this video as I have one of these 135 watters. I completed the master volume delete and the reverb bypass cap and I am glad I did. Great improvement! Without your video I would have been lost. THANK YOU!!!
You're welcome, Pete.....glad it was helpful.
Thank you Uncle Doug, Bless you for sharing your wisdom with us!!!
You're welcome, F1. Likewise on the blessing :)
Loved Jack's disappearing trick. He's a real character.
He is a master of concealment, Sean :)
A real ninja! 😁
Sean Kerns , cats move seamlessly back and forth, multiple times a day, from the visible world to The Upside Down dimension.
@@goodun2974 ...possibly.
This is way over my head, but it's nice to know that there's still someone out there that still understands this stuff. I remember my friends did their own repairs on their amps/guitars in the 60-70's.
Nice mod! I own a 1973 Master volume 100W and I don't like so much the sound, I 'll try this!
Good luck with your modifications, Frank.
Variable NFB control and reverb upgrade are genius, what a huge improvement! NFB is like having a on amp compressor...really cool.
I'm glad you liked the modifications, S.
Mr . Uncle Doug when after 12 yrs. of reading tube amp books, electronic books I went down to guitar center ( the old cheap G.C .) An got one of these, it had beach sand an sea shells in it , homemade backpanels anyway..... That's the one l made all the mistakes went back an fixed l learned everything literally from that 135 watt ultra- linear twin reverb I had that head in there and I swear about 100 times! I love that amp now . Pretty much back to the old Twin rev. Design except .. l did keep that Big Ass power tranny I like 500 volts on the plates, turned the hum balance into a rear accessible Bias pot, got 4 R.C.A. 6L6GC's in there too it's Killer!!!
Thanks for sharing with us, Gary. Continued happy coexistence with your Fender Twin.
Great job on this video Uncle Doug. As an engineer and guitar player I was very appreciative of your attention to details and troubleshooting method.
Thanks, Steven :)
Just finished the removal of the master volume and replaced it with the adjustable negative feedback, as well as deepening the reverb and slowing down the tremolo. After replacing caps and resistors. 1980 Fender Twin UL sounds amazing. Thank you for being an amazing teacher.
You're welcome Michael. It sounds like you made some excellent modifications.
I learned the boost trick by experimentation when I was 8 years old. I just unplugged the two reverb cables form the tank and connected their center pins. Instant overdrive. The reverb knob now acts as a gain knob. I still have that old Supro Sportsman...
I know nothing about amp electronics or any electronics. Never should have watched this to the end but i did because the explainations were so clear I was fooled into thinking i knew what he was doing. I didn't of course, but he made what i normally would find tedious interesting. Hats off! If my Deluxe Reverb ever needs work, i know where i'm sending it.
Thanks so much, Jack. We really try to make the videos clear and concise for all levels of viewer understanding. We would welcome your amp for repairs, should any become necessary.
That amp was nice,but your Hot Rod looks and sounds excellent.Nice improvements on her.🎸👍🔌
Thanks twice, Bob :)
This guy is so fun and entertaining with his dry humor, I could hang out with him all day.
Thanks, Luke. You're always welcome :)
A new video from Uncle Doug = happiness!
I hope you enjoy it, Riccardo.
Cheers Doug from Au. Thanks for sharing your experience & wisdom.
Valuable knowledge that anyone into tubes should read. When buying a car wise people go with what mechanics recommend. When buying amps go with what a veteran tech like you recommends.
GOLD!
Thanks so much, GF :)
Thanks for doing a video on the mighty Twin Reverb, I've never owned one but still like the classic sound of a good "Twin"
You're welcome, Gary.
Loved tube amp for 40 years but tired of these constant problems and maintenance. Bought a Quilter and will never go back lol. Great channel BTW but reminds me why I sold my tube amps.
I understand, Tele. Thanks for your input.
I have this same amp Uncle D, only from the 60's, mine don't have the push pull master and been wrenched on several times and yes very loud amp! wicked amps when cranked. good video mang!
Thanks, Randy :)
You have that one cooking,best 13 twin I have ever heard,been at it for over 40 years.THANKS.
Wow.....thanks so much, Frances:)
I repair at least 30 of these amps a month. Most customers want them Blackfaced. (Rewire it to 1960's schematic) But the one thing I do on all of them now is to Blackface the bias circuit. Makes the balance pot back onto a true bias pot. Just a suggestion. Also if you ever need tubes or parts I stock everything and have over 4000 tubes. Thank you for your videos.
Kevin
Tube Tek Chicago
You're welcome, Kevin. I will keep your offer in mind.
Kevin, i have many tube amps, always looking for good tubes, especially 12at7's, true 7025's? Military grade 12ax7, how you set for 7025's?
I do. Not sure what at this moment. I just sold a sealed 5 JAN 5751 tubes. I have some Mullard and Amperex including a 7025 labeled Mullard. I have several RCA 7025 but they are not new. They test very strong. I have bins full of NOS and used 12at7 and 12au7. Have a lot of 12az7, 12av7 and 12dw7 also.
@@kevin2960 i tube my amps for guitar, so i need AT7 for phase inverter and reverb stages, and 7025 for most other stages, the Jan 12AT7 is best store bought reverb ones I've found for matching original sound, those groove tube 12at7's are horrible IMO, too noisy for reverb. Phase inverter less sensitive i think, I have DLR, VBR and Twin all need retubing, and a Victoria Regal 2,also needs same compliment. And Peavy DB needs good 12ax7's. Many times the stuff i order is microphonic out of the box, frustrating
I quick test on a BK707 and then test everything on a hickok 533a. Preamp tubes I tried to test in an amp also for microphonic noose. Power tubes I can match on a maxi matcher
Hi Doug.
Thanks for the reply.
After carrying out the master volume to NFB modifications I noticed slight interference so I fitted a shielded cable on the pot output, much improved.
Thanks again for all your lessons.
Trev
You're quite welcome, Trev. I'm glad the modifications were successful.
Props to you Uncle!
I’ve got two of these (one with MV removed)
I’m really blown away by how many other people have one too.
I recently did half power mods to both and it makes them more usable (and perfect as pedal platforms)
As long as you stay on top of your power cap maintenance this amp will not die (I’ve had #1 for 30 years)
Super Linear Nation!
Thanks for the input, RT.
Man what a nice work! 😮
I own a silverface twin 135 W with the original orange JBL120 in it. The Amp belonged to a good musician friend of my Granddad (hope they jam in heaven together) and I love it. It's 1000% all original, every single part in it. It sound's very nice. I only play it in my home studio and I cant understand, why so many people hate those silverface amps 🤷♂️
Thats the best sounding fender I own. Yeah, the handwired blackface I use live allso sounds very very great, but nothing beats the silverface 😁
I agree that SF Fenders are often overlooked and underappreciated, Hattra.
A giant schematic. You could use this for wallpaper - love it Uncle Doug
Thanks for that video. It brought to me many memories from my father. He started very young modifying home radio receivers (mostly phillips), to increase output power. Back in 1970 he assembled a 60 watt 2xel34 amp for his marriage party. Later on he found this 100w fender schematic and assembled. Finally he found the 135 w schematic and modified his 100w amp to it. He lastly assembled two 135w amps in a single chassis. We could never reduce the hum problem. He passed away in 2009. This video reminded me of happy times tinkering with him and his tube amps. Thanks again.
You're welcome, Oscar. Your father sounds like quite a capable fellow.
Great video. I have personally rebuilt two of these in the past. They are great platforms for turning into blackface Twin Reverbs. What was not mentioned was that the output transformer has ultralinear taps connected to the screens and the power supply has no choke. It has been said that Fender(CBS) did this to make the amps cleaner. It did not sit well with players as they sounded somewhat sterile compared to blackface Twins. I like that mod where you add the presence control although I would have used a 5k-l pot instead. Thanks again for another great Fender repair project.
In all the excitement I forgot to mention the ultralinear screen taps, Arnold. I too would have preferred a lower-value pot, but it was all I had on hand.
Arnold Shaner , the Super Twins made more sense for pedal-steel players, most of whom play ultraclean*, than for regular guitarists. Actually, I came across a Super Twin at a huge outdoor antiques show some 20 years, which had 3 or 4 piezo tweeters mounted into the baffle above the speakers (holes had been drilled for the tweeters). As I recall, the seller wanted something like 600 bucks for it. Thanks but no thanks! Antique dealers rarely sell musical gear at a reasonable price....although, around that same time, I bought a doubleneck Supro lap steel and a screaming little Valco built Airline amp with field coil speaker from an antiques dealer for $225....
*This attitude or aesthetic might be changing somewhat now that you have folks like Robert Randolph tearing it up on screaming pedal steel....
I hope you are still around when I need my toys worked on! You are one smart man and a great technician. Thank you very much UD!
Thanks so much :) I hope so too.
1 dislike? Probably from the "tech" that "repaired" it previously LOL
Either that or they let some Bellevue psych patients loose in the computer room again :)
popeye What kind of Tech would install those shitty pots, and then wire them wrong?
@@UncleDoug Maybe some meth head shredder in a hurry to "fix" it. Are you trying to give psych patients a bad name?
@@MrBuggmann Nope. Some of my favorite people are psych patients, Mr. B ;)
Just want to say, I've been trying to teach myself the inner workings of amplifiers and their circuitry. Every video you have uploaded is a tremendous wealth of information. Can't wait to go through all of them. I've already finished Capacitors 101, working my way through the resistor series and just stopped off to take a break with this video. Still so much info to absorb and learn from. Thank you for this.
You're welcome, Jeff. We're glad the videos are helpful :)
You are my favorite channel on this subject. Thank you for excellent quality content Uncle Doug :)
You're welcome, RL. That's always nice to hear :)
Dear Uncle Doug- your instruction has been extremely valuable to this Boomer. I actually managed to get a 1979 Silverface Pro Reverb up and running (with some professional help) and great results. An identical 1978 Pro Reverb sits on the bench now for component upgrades. Again, thank you so very, very much for all you do. ❤❤❤❤❤
That's great to hear. GG. Continued success :)
you're a miracle worker Uncle Doug
Thanks, Mr. P :)
I have a very nice 65. I just had it repaired after it was in the attic for 20 years. My retiring repairman said in 45 years of amp repair, it is the best amp he has ever heard. I was very gratified to hear that. I traded a BF Princeton in on it in 74. I put some Vintage 30s in it. It is unbelieveable clean power. I had a silver face TR in the early 70s. Sold to my roomate
Wow......I think a lot of us envy you, M33. That sounds like a wonderful amp.
Thanks! I just discovered your channel...nice. Too bad I can't pick it up by myself anymore.Before he retired, I asked if I could bring all my tube amps to him as he repaired them. I would drop one off and the bring another. Now they are all good to go.A 1978 Red Marshall 50w I bought new, A 1965 Gretsch Bass amp (Valco Supro) Great Guitar amp, I got at auction, a little Alamo and my 1967 Dual Showman has never needed repair I have had for about 25 years. I used that one quite a bit. Thanks again, I'll be watching!
It's a shame that your repairman is retiring, M33. We really need all the good techs we can get. One consolation, I have personally retired several times, but couldn't resist coming back. Maybe he'll feel the same.
That is why I asked him while he was closing his shop. He took them home to do the work. As far as I know, he is the only one that knows the tube stuff inside out in an area of about 350,000.I'm grateful he helped!
I especially loved watching this video as I bought one of these used ('78 best I can tell) from a guy back in 1982. Say what you want about them but I just cranked it up after watching the vid and with the master at 10 (not pulled, very bad the pull) and every thing else dialed into player's discretion it still sounds warm and loud and clean and its an ideal platform for pedals. It does weigh a mother-ton and a half though so it never leaves the house anymore. I have so far been resistant to altering the circuit it but these little tweaks might be just my speed as they could easily and quickly be returned to spec. Thanks again for another great vid!
You're welcome, Keven.
Thanks for the Video. I bought my 1968 Twin Reverb amp in the mid 70s and it still sounds like it did 40+ years ago.
You're welcome, QP. I hope it continues to serve you well.
Oh course it hummed. It was too stoned to remember the words...
Literally, LOL!
It's been passed around too much.
ARRRRGWAHAHAHAHABWAHAHAHAHA !!!!
You are brilliant! Thanks.
YOU BETCHER LIFESAVERS!!
This guy is brilliant in his dedication to repairing antiquated tube amps. Watching this repair video makes me appreciate my Boss Katana all the more. It probably cost the customer more money in initial cost plus repair of this thing to come close to a decent modeling amp in price. I'm an old tube amp guy but today this sort of repair process is ridiculous!
Thanks for your initial nice comments, William, but apparently the process was not ridiculous to the owner.......and, let's face it, in this circumstance, his is the only opinion that really matters.
Am I the only one with CCR in my head when he hits that tremolo channel? 'Midnight Special' just kept coming.
I thought the same thing
lol me too
Of course
In my career I have repaired hundreds of pieces of equipment. Mostly in RF and broadcast. I know what a headache it can be sometimes. Even if it's wired factory correct! You sir are a trooper! I would have had a few more choice words to say running into the dipwad work you ran into! You held yer tongue on camera. Nice rework job! I hope you charged him accordingly!
Thanks so much, SBE. It's good to hear from a fellow repair guy.
I have one of these 1970s Silverface Twins. I do not use it for gigs and have not since the 1990s. Far too heavy to carry around. It does sound great though!
Now, that's my kind of consideration! SUPER-well-packed, Easy-to-read SUPER SIZED schematic, thorough explanations...! WONDERFUL! Always been a big fan of the Twin Reverb.
Uncle Doug, you are the quintessential teacher. (LOVE the drone and the cars, too).
I agree, Dave. The owner of the amp is a real classy guy......which is why I went the extra mile with it.
Great Mods Uncle Doug..!! I will do that to my 1979 Fender Twin...these twins always sound better with JBL D120F speakers
Everyone says that, Mr. G. It must be true. Thanks !!!
As usual, “old guys rule”. Exceptional work Doug. You are truly an artist. You give the name “Tech” the true meaning. I’m jealous. Well done my friend.
Wow, thanks so much, Phil :)
Interesting, both the repairs and the mods.
A spectacular performance by Jack and Ollie! And what an academy award-winning finish! Who knows what is next?
Indeed, Sting, so stay tuned..........................................................
The name is ultralinear, Jerry Garcia cherished this model. Again for the test you need the jointed pine cabinet and TWO orange JBL special design for Fender speakers, lush reverb and vibrato on about 5 all around master cranked, volume at about 5, sound fills the canyon, this is a Day on the Green 70's Bill Graham gig Twin.
I knew a guy who played with Maria Muldaur band in mid 70's, used 2 of these Fenders, trick, in volume 1 out of 2 into 1 of the second amp, that's a big big sound! Again guitar in 1, line out 2 into 1 of the second amp
Comic Blues with Jonygitar, Maria Muldaur! A terrific singer, I saw her sing a couple of times back in the day. Free concert in a local park around 1979 or 80, probably had 10,000 people there. A few years later, I saw her in a small club a few minutes walk away from that park, I don't think there were more than 30 people in the audience. Which only goes to show how fickle music audiences are. I also saw her at the Edmonton Music Festival in 1992 (Csnada) along with about 60 other performers on 5 stages. Her ex husband Geoff was playing elsewhere at the festival. Man, she can sing; she was HOT, in more ways than one! She was quoted in an interview once as saying " I'll still want to be a singer even when I'm not so hot to look at anymore."
Who was your guitarist friend from her band? And on the subject of guitarists in bands supporting female singers, when I saw Lucinda Williams, guitarist Gurf Morlix was using a pair of blackface Twin Reverbs....
A tremendous effort at deducing the overwhelming issues possessed by this Silver-Face twin. The amount of repair required included schematic instructed wiring, as well as some old-school reverb modifications. Judging by the way the pots were wired, I'd say the joint left inside the chassis belonged to the tech who last worked on this amp. He/she was obviously baked while attempting a repair. It is evident that whoever this was didn't even realize they dropped their joint after burning their lips while trying to light it with their soldering iron. This is an idea for a new t-shirt slogan: Kids, never let a stoned tech work on your amp. All you'll get out of it is a dead amp, but a pristine joint. Well done as always dear uncle. Enjoy what's left of the weekend.
Thanks so much for your comments and very amusing analysis, Alex. I needed a good laugh. ;)
Been a while.. Glad you're back...
Now I'll watch the show... 😁👍
Thanks, James. I hope you enjoy it.
Exactly so !!!!!
Uncle Doug has a brain like a super computer. He not only knows his amps, but he's a hot rodder too. Nice car Uncle Doug.
You are too kind, John ;) Thanks !!
Great amp, better tutorial AND a neat ending? You are spoiling us =D
Thanks, Daniel. We are trying to please :)
Fascinating video. I bought one of these privately around 1986 for $650. The seller told me it was and early 80s model but I never verified. It sounded lovely though it had some annoying but tolerable buzzes when the reverb was turned up. I never had any serious work done on it but I eventually sold it because it was just too damned heavy. My knees would literally buckle when I lifted it into my hatchback. And I was a young man. I really miss it but don’t miss the struggle. After years and many different amps I’ve finally settled on a silver and black Fender Supersonic. I’m happy with it though it had its share of troubles. It has a single 12” speaker and is much lighter though still a hefty 60 pounds. Currently the reverb emits a microphonic feedback which I need to get diagnosed. Hopefully it’s an easy fix as the reverb is quite nice to my ears.
Glad you liked it, Ralph.
I love the ultra linear twins and the 100 watt mv versions as well. I have really dirty pedals, and the twins laugh at them. Marshall's tend to fart out with my pedal rig. My slp 1957 heads don't but they are more like a bassman than later Marshall circuits.
Uncle Doug...you are truly amazing. I feel like I’m taking the much desired course in amp repair. Your patience and knowledge of these wiring diagrams inspires me to learn. You’re one of my very favorite channels. I used to go to a character here in Southern California named Red Rhodes who could easily fix my vintage amps and he was so much fun to talk to. I treasured my time with him. He also played steel pedal guitar so sweet and can be heard on the timeless class Sweet Baby James and many many others....plus he also built hot rods like someone else I know. Sadly he’s gone now and I miss him but you’ve filled a nice empty space in me. So glad you share your passion with us. God bless you.
Wow, thanks so much, David. I am honored by the comparison.
That transformer is the same size that powers our subdivision ... Lol ... Good vid as usual . Much appreciated and enjoyed ...
Thanks, Eddy. Dr. Frankenstein could have used one :)
Ultralinear, my back can't take moving this one anymore
I have both a Fender pro tube twin and a Boogie S O B. The transformers in the Boogie are huge compared to the Twin. Even with 2 12's the Twin is just about 5 lbs heavier than the Boogie.
Thanks for making this video. I have the exact same amp with a few minor problems I haven't got to yet. (No gradual warm up, just BAM pops on all at once. Too much hum). This will help me troubleshoot it as this one is a little different animal than most twins and you answered a few questions I had. Luckily I'm the original owner and do my own repairs so it's never been monkeyed up by someone else. It's actually been a great amp for the first 42 years. Tubes, a few speakers, replaced the bass pot that got snapped off twice from lugging it around from gig to gig and re-soldered the reverb but that's about it. Solid as a rock. It's outlived many of my Marshalls. Maybe I'm just lucky :) Thanks again !
You're welcome, G. Best of luck with your Twin.
When I went to GIT in 1984 I used to hit up the local Hollywood music stores for old amps (vintage,what's that??) to learn repair and mod. One day I scored for $75, 3 FENDER AMP CHASSIS''. A 62' BROWN FACE BASSMAN, 65' BLACK FACE BASSMAN, and a 74' SILVER FACE TWIN REVERB. ALL WERE BONE STOCK, but the Twin had a single transistor input buffer added, and a Master Volume. I repaired all three without much difficulty.
(Scroll down and read the ******* paragraph 1st...or just wait)
I DISAGREE WITH YOU ON MASTER VOLUME ADDITIONS, ESPECIALLY ON 4-EL34/ 6-EL34, 4-6550,and AMPEG V4 amps. A SIMPLE 100% NON-DEFACING, easily reversible (on hand wired amps) PHASE INVERTER MASTER VOLUME Consists of 3 parts! 2 capacitors mounted on a duel pot! THE DUEL POT (mounted in an EXISTING HOLE, [DI, AUX SPKR] ON REAR OF AMP), 2 CAPACITORS (MOUNTED ON THAT DUEL POT), and you are only desoldering one end of each of two phase inverter caps (secure, duh). Two wires from those 2 caps to the pot, and two wires back. THAT'S IT! CRANKING THE MV PUTS CIRCUIT BACK TO STOCK.
HERE IS A MORE THOROUGH, REAL LIFE EXPERIENCE BLURB ON MASTER VOLUMES. NOTE, I prefer no mods on Fender amps, but a MV is easily 100% reversible on hand wired eyelet boards. 50 watt or less amps I prefer "ONE WIRE" (one resistor) CASCADED CHANNELS. It was a 5 minute professional quality mod on my 50 Watt Sound City head. I hate FENDER CASCADED PREAMPS (aka Mesa Boogie Mk I "Santana amps". That said, read on and ALWAYS FOLLOW TUBE AMP SAFETY PRECAUTIONS.
-------------
I have the 100% tube, 1973 DALLAS ARBITER (manf's of the Fuzz Face)Sound City 120R amp head. A MUST is the simple 3 part, non invasive POST PHASE INVERTER MASTER VOLUME, robrobinette *DOT* com/The_Trainwreck_Pages.htm
Just put the knob on the back in place of LINE OUT if you don't want to drill a hole back there. In a twist of amazing luck the 1982 issue of Guitar Player Magazine's HOW-TO *PHASE* *INVERTER* *MASTER* *VOLUME* article came out the exact same week I bought my Sound City 120R! Immediately installed it. It opened up a world of distortion the amp is damn near incapable of with those HUGE Partridge Mains and Output transformers, and with 6-EL34's! I'm telling you, DO IT, you will be in 7th heaven with that beast. 😊
*******Opening MV knob puts the amp back to stock, but why, the SC amp's sweet spot is like 3/4 MV if you want it loud with picking dynamics clean-to-power chord bliss. Saves power tubes and speakers.
ATTENUATORS ARE SO OVERRATED! UNLESS YOU WANT TO SOUND LIKE SANTANA, TOM SCHOLZ, or BRIAN MAY, why do you want to squash your entire impedance dynamics? A great amp sound is the interplay between the preamp, power amp, and speakers.
For the life of me I can't find that simple simple GUITAR PLAYER MAGAZINE, MASTER VOLUME ARTICLE online anywhere. It is the same circuit that is in the Train Wreck manual. Just google:
robrobinette *DOT* com/The_Trainwreck_Pages.htm
I had a 50 WATT SOUND CITY head and it sounded great with a simple 1 wire, resistor jumper from channel 1's preamp tube's output into channel 2's input (grid on tube). And yeah yeah consult Groove Tubes manual, that whole ball of cotton.
I bet we know each other, i was in Hollywood 1984,all my pals were at GIT. Did you play Tuesdays at Central?
Brilliant work Doug. Thanks for saving another one from the landfill. Finding knowledgeable service techs is a true rarity today and your videos are most enjoyable and informative.
I bought a 1969 Pro Reverb about 20 years ago and it used to drop out with regularity when it heated up. After several visits to the local tech, he finally re-soldered the entire board and it appears a loose ground was the problem. Details. Details. Yes, these things ain't light! But they sure sound sweet when kept in original shape.
Yep, the little things can really get you down :) Thanks so much for your very nice comments.
Giant schematics of historic circuits for wallpaper...hmmm...yes, please 😊
I agree, GB, we need to patent the concept.
@@UncleDoug hmm i have done this when i repaired/restored the Graetz 177and the Saba Freiburg Automatic 3D and put it on the wall next to me, for easier workflow and to put some notes easily into ;)
UD, Really enjoyed your 78 Fender TR Video. I worked on amplifiers for Fender at the Fullerton plant from 65 to 69. Also a musician. Now at 75 retired from my career in Financial services Dec. 1, 2020 in Rio Rancho, NM. Set up shop and recently acquired cheap a non working 79 Super Reverb Ultralinear 70 watt with MV on wheels. Saw you video and recognized the Twin Reverb Schematic Frontend is identical to the SR Schematic. My 79 SR has a frozen MV pot. This amp is all original, had the wrong fuse 1 amp fast blow in fuse holder that blew immediately. LOL and the guy who I bought it from said he purchased it new. Use it for his Roland Piano. He had a vise grip on the MV. Go figure. I am going to get this puppy working. I love the Fender SRs, the first amp I ever owned. Missing knob on MV and knob on normal channel Volume, but everything else intact. Opened up chassis and can, all original. I want to replace the MV without the push pull. My question to you is what value pot should I use and should I just put in back in the same position in the Circuit, which is the same spot as the twin circuit before the 12AT7. I like your blackfacing the Reverb Cap idea too. I joined as a patron and really appreciate your valuable knowledge and helping a old man get back to doing something he loves. I am a Tom Petty fan and perform many of his tunes in my act. "The Waiting for the Parts is the Hardest Part." LOL
Greetings, William, and thanks for your very nice comments. Have you tried to disassemble and repair the original pot? If not or if it was not possible to do so, then I would concur that replacing it with a pot of equal value in the same position within the circuit would definitely make good sense. I am not an expert on MV circuits and thus cannot offer any insider info on them, other than to wish you the best with your project.
@@UncleDoug Thank you for the feedback. The original pot is trashed, I tried but to no avail. I think the vice grip did it in. On my 79 SR Schematic it says 1M - JT for the value of the MV POT. So 1 meg, thats easy, but what's the JT stand for?? Just getting my chops back on reading schematics. The push pull boost I will be leaving out and removing from circuit. So just only need the appropriate MV POT. Putting in a order today to get all the parts I need, this was the only one I was a little confused on.
A 135 watt Twin??? That sounds like a weapon of mass destruction, lol. Or at least for inducing earthquakes... A while back, Johan Segeborn did a video of him plugged into a cranked Twin. Some sweet sounding overdrive, but even he admitted he may have gotten a bit too ambitious there, lol. He said it was painfully loud! (Coming from a guy who makes videos of cranked Marshall full stacks...)
I just recently picked up a 1977 Twin Reverb Silverface. It was played maybe once, and just sat in the guy's closet for all that time. It is in prestine condition with all original parts, and no mods.
That sounds like the find of the century, Steve. We are all jealous !!
Man that amp sounds good ,nice playing there really enjoyed it your the best,ha ha ha nice ratrod love it
Thanks, Joe :)
I have the Silverface Dual Showman Reverb with the P/P master. Mine is the 100 watt version. Has the standard x-formers instead of the huge Ultralinear x-formers in the 135 watt version you've got on the bench right now. Thanks to your clear and concise video and explanation on removing the P/P master mess I'm finally going to do the same thing to my amp. Going to add the NFB control as well.
Best of luck with your modifications, Carl :)
I love my Twins !
I was beginning to worry that you were unwell...great to see & hear you again.
Thanks, Ray. Despite psychiatric diagnoses to the contrary, I am alive and quite well :)
Yes about the master vol... even Leo did it with his MM trying to give overdrive at lower vol I guess...
I own the same amp. Love the beast but I can barely get it up stairs. It had JBL D120f speakers with one blown. I replaced with Eminence 12s but kept the old speakers. It's slightly lighter and still sounds good with pedal steel guitar. Thanks for posting this repair. You're the best.
Thanks, Larry. I guess you'll need to install a freight elevator :)
We called that one the evil twin.
Wow. Excellent work. You are truly a master of your craft. I can’t begin to imagine the things you’ve seen in your career to be able to casually troubleshoot the amount of wrong involved in this repair. 👍👍👍
Thanks so much,, JM. Experience definitely is an asset :)
"I can't see jack." Something I say every time I try to find a particular component when I'm looking at a new (to me) schematic. :-)
Jack has copyrights on all use of his name, so send $10 every time you say it :)
@@UncleDoug I laughed so hard that I snorted.
@@kenhanson4015 Good to hear, Ken. I guess that's the only legal snorting we've got left.
After one month in the Arabian desert in a a-hole country it is quite nice to be back home with Uncle Doug and his amp adventures.
That motorcycle sounds sweet too.
Thanks, Erik. It's good to have you back.
You should frame and hang that schematic in the ol’ man cave Uncle D!
I've marked it all up, but it's still a beauty, Whipp. Maybe I'll do that :)
Your documenting your work is such a blessing to society. Thank you
Thanks so much, CP :)
@@UncleDoug you have taught me so much. You have inspired me to do my own diy soldering work on gear I will be using for recording and performance, and soon it will help me start an amp building journey as I tackle trying to make my own Marshall. I have all the parts. Wish me luck!
@@TheChadPad Thanks for the very nice comments and best of luck with all your projects and endeavors, Chad.
@@UncleDoug Thank you Uncle Doug! God bless you
Looks like you had fun! At the end of the video the current limited was still glowing, is it supposed to do that?
Yeah, I was wondering about that, too. It was almost mesmerizing!
Yes, the bulb is correct for the lower-wattage amps I generally work on. In this case, it was inadequate for the 135W TR, so it tended to glow brightly when driven.
ya know even after 4 years I think I've watched this 20 times. thanks, Doug. I for one, are very sad you've retired . I have loved watching. sorta like my late nite Johnny Carson. you'll have to do a finally show .
Thanks, ICFA. We are retired from our normal job, not from making videos, so new ones are being posted about once a month
@UncleDoug oh fantastic so you would take on other amp projects, I'm super happy to here that, I look forward to seeing them.
We have posted a couple new videos just recently, and intend to post more in the future, ICFA. Please check our video list.@@icanfixanything4u2
Crap... I don't have a beer :/ gotta pause the video :D
Hurry up man, we’re waiting ;)
I have this exact amp housed in an oak cabinet head, built by me! It’s a beautiful piece of furniture the Amish would be proud of! I think I may need to reinforce the floor where it sits in my studio!
It sounds wonderful, John. I am a big fan of exposed wood cabinetry and salute your creation.
I’d advise against removing the master volume. Just set it to 10 and it’s out of the circuit. I usually set the MV on my ‘74 Twin Reverb to between 6 and 8, as it allows my to set the preamp volume higher and tames the amp a bit. The pull boost is useless but it’s totally out of the circuit when pushed in, so does no harm. I’ve considered repurposing the switch, maybe to increase the negative feedback resistor value. I don’t need to continuously vary negative feedback. I left the bias balance pot in place, but added a trim pot in series with it, which allows me to adjust both.
For those that don’t know, 135 watt Twin Reverbs used an ultralinear output circuit with additional taps in the primary of the output transformer connected to the screens of the output tubes. I think it provides additional negative feedback to keep the amp clean at higher power. The output stage voltages are also much higher.
My ‘74 is the 100 watt circuit, which is way more power than I need these days. It sounds yummy though.
funny i just commented the same thing ,never understood all the negativity and with a master you have the choice of dirtying up the amp even if using outboard gear or preamps like I do , I found with the MV at 10 to be the same as if no master at all was built into the amp
Your obviously more knowledgeable in electronics than myself wish I were but........having owned 4-5-6 of these beasts over the years using 2 on sage when space allowed ,Ive never owned a twin with the boost switch though . All 100 watts what this amp has always needed though was a op power select switch instead of yanking 2 tubes to get i down to a small club working volumn and still have tone
Leaving the MV circuit in place is not quite the same as removing it all together. There will still be some minor loading of the tone...in theory. Whether you can hear it or not, and whether its worth the time and trouble is up to you. However, I do like the way Uncle Doug put in the variable NFB/Presence control.
From Leo Taking in previously rebuilt work is a real test of patience. You are the master of patience. 450-YF is a CTS pot , those used to be pretty good. Nice save. I have one (85 watt) and it easily walks right over the top of most 100 watt solid state guitar amps. I gave up on carrying the Twin reverb around, too heavy. I even took the casters off of it and bought a hand truck just for moving that amp.
These two volume pots were absolute junk, Barb. Maybe they were counterfeits :)
Who gives the video a thumbs down? Why? 🤦♂️
Rumor has it that it's a leper whose nose fell off and hit the "thumbs down" key.
I love the way the current limiter would just start to glow as you played. Great video Uncle Doug.
Thanks, Bill. It's an excellent indication of the increase in current flow to (and through) the amp when it is driven by an input signal.
Turn it up to a "Not so Seismic-Level" .
Uncle Doug is the coolest. I love these videos! I really dug the short “Interstate Love Song” jam. Good taste. Great instruction. Thanks for another great video, sir!
You're quite welcome. JM. Thanks !!
Delivered by Emerson, lake ,and palmer I see !!!.
Yep :)
Indeed, that is some super-pro packing that guy did. Makes my packing jobs look like I just pissed on the thing and taped up the box. I bow to a master..
We have received several of those peed-on shipments, C.....and much prefer the type of packing seen in this video :)
Steam powered Harley Davidson motorcycles were made popular in Ohio in the early 80's by the infamous motorcycle gang the "Cleveland steamers" !!!.
@Sandpile Sammy ...but you did...so now tell yer friends and spread the word that the gangs getting back together !!!.
@Sandpile Sammy ...I see your a cb fanatic...me too...been active since 1980...good to meet yer !!!.
Nic White , the original "steam-punks"?
@@goodun2974 ...WORD !!!
Greetings, Nic. Thanks for the info :)
Love your videos, learned more in a few of your videos than I have in years. Thanks Uncle Doug!!
I would turn the master volume to 10 and use the preamp volume for volume control.
That's not the best way to get good tone from this type of amp. A Twin doesn't sound its best until the volume control is at 3 at the very least. With the master at 10 that's just deafening.
UD. ...the high budget outro was just the best. Noticed you still had the beast on the current limiter even during the audio demo. Really loved your live demo of all the controls, that really brought the possibilities of the amp to life. You are fearless in pointing at parts of a running amp... even leaning right over to point out the vibrato socket... Perhaps your toils are not completed here but the things you have shown us are just wonderful. Good luck with the final wobbly push on this one.
Thank you Uncle Doug for what you do.
Thanks so much for your kind comments, TIL. High current-draw amps like the Twin must be biased using wall AC (no CL). After the biasing or for video staging, anything goes ;)
Those 1970 Fender amps have horrendous wiring and lead dressing compared to the 1960 versions.
@@Carlosant - no, because most fender assemblers were women, mexican women, even back in the 50s
It always amazes me the neatness in wiring between a tweed, brown, and blackface amps versa a silverface amp.
I guess things got a little lax under CBS, Mike.
Running for Corona Extra w/lime...
Sounds good to me, PC.....get two while you're at it :)
@@UncleDoug Yours is getting warm.. Let me help you with it. Oooo, gotta love that Twin...
@@PipeCat1965 Twins are my favorite amp.
@@donaldheitger6731 Ya just can't beat 'em, unless you need something smaller for some occasions.
twins are by far the greatest clean tube amp, also the greatest electric guitar amp.
My friend has one of those Fender Twin Reverb. I last seen him in 1987 he said he still has it and he still jamming with it!
I hope he wore ear plugs, Ronnie :)
A better example might be an electric Harley Davidson :)
Unfortunately, they have done that.
At 15:10 I shuddered, at 18:00 i became ill. Wonderful work and incredibly instructive. Give this man some love$
Thanks for your support and understanding of the challenges of such a repair, Clarence :)
I think ditching the boost was great...but I would have kept and converted the MV to a post phase inverter MV
Thanks for your input, Dave.
This, 100%. Or even pre-phase inverter, like a regular voltage divider volume control. Master volumes rarely make an amp sound bad unless they are some weird design. Turn it up to 10, and it's virtually out of the circuit. But if you own one of these beasts, you already know what you're getting into as far as clean volume goes. Even a MV won't save you from setting the amp to the infamous .05 on the volume dial...
@@JulianA-tr6pt Did you replace the MV pot with a different pot? I have a 79 SR with the same mv curcuit, MV is damaged and needs to be replaced. I like the MV, took the push pull out of the circuit. Trying to figure out what value Pot to use and where to put it back in the Circuit, same place or is their a better spot for the mv.
@@williamplatte7318 I was speaking about my experience with the few amps I've built, which are much lower powered 2xEL84 amps. Personally, I just stuck the master after the preamp stage & EQ, before the PI. 500K Log, cause that's what the amp originally had before the rebuild. Worked for me since my amp has a cascaded preamp with EQ after the two 12ax7 stages, so it can get some good preamp drive with the master down.
On a Fender, which is cleaner for a variety of reasons, I'm not sure what would be the best, but I imagine most MVs would sound good. I haven't experimented much with post-PI master vol, but it definitely can give you more distortion. They can get more complicated, of course, with dual pots and safety resistors.
@@JulianA-tr6pt I think I am going to put it back in the circuit before the PI. Per the schematic it calls for a 1 meg JT pot. The original push pull pot that came out had the typical three solder joints on the top and one on the bottom of the pot and four solder lugs on the push pull switch. Since i am removing the push pull I was looking for a 1 meg JT pot that would just replace the one that came out. Any ideas on where to find such an item? Antique parts has one, but it only has the three solder lugs on the top and no solder lug on the bottom according to the picture. I went ahead and ordered that pot and see if I can make it work. I will update when I get everything up and running.
I bought the twin version of this amp in 1961 through a Sears catalog store in Falmouth, ma. I was stationed at Otis afb at that time and played in a band around cape cod. Great amp. I used it until around 1980. Repaired a few times during that period. I gave it to my son, who sold or traded it. Wish I could find it and refurbish it again.
Are you sure it wasn't a Silvertone, PV? I was not aware that Sears sold Fender amps.
@@UncleDoug It was a Silvertone. copy of the Fender twin.. Same tube compliment as the Fender twin. Was a great amp. I used it for about 20 years...