Commonwealth Pro Audio - 1973 Fender Twin Reverb Partial Restoration

CommonwealthProAudio.com
Here's a '73 Twin Reverb we bought to restore to glory.
It had a ton of issues that we addressed:
cut off power cord
mismatched and missing tubes (power and preamp)
shredded pots
blown speakers
out of tolerance grid resistors
Time Stamps:
0:15 - Accessing Filter Caps
0:33 - Mismatched and Missing Power Tubes
0:41 - Testing Power Tubes
0:57 - Testing Preamp Tubes
1:15 - 12AT7 in the Wrong Position
2:12 - Verifying Correct Fuse
2:48 - Replacing the Power Cord
3:38 - Mistakenly Cut the End of Ground Wire
3:50 - Fixing Mistake
4:42 - Black Wire o18:03 - n Power Cord
5:45 - White Wire on Power Cord
6:18 - Testing Amp Through Light Bulb Limiter (LBL) to Verify Power Trans.
6:31 - Inserting New Power Tubes
7:10 - Testing Amp Through LBL After Tubing
7:43 - Cleaning Pots, Switches, and Jacks
8:30 - Detailed Visual Inspection
9:40 - Example of Connection Issues
10:56 - Checking Grid Resistors
11:48 - Checking Screen Resistors
12:27 - Checking Other Resistors
13:12 - Replacing Two Potentiometers
15:24 - Testing Amp w/ LBL & 16 ohm Load
16:48 - Checking Speakers
17:31 - Checking Reverb Tank
18:03 - Testing Amp at Full Power w/ New Internal Speakers
21:59 - Replacement Parts Overview
22:09 - Sign Off Follow Andy on Spotify:
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[@garybateman6869]

I love my 74 twin Reverb. Sold my dual showman to get it.

[@Tonetwisters]

Mighty tight amp! I have a '76 and it's an el beasto.

[@larrydering1598]

A great amp with fantastic tone. Nice work. I have rebuild a couple. Well worth the effort.

[@TheBrothaAB]

Thank ya!

[@anthonyrichard461]

You can run a Twin with two output tubes instead of 4 but they have to be the two inner or two outer pairs. This was done to be able to crank the amp without out peeling the paint off the walls. It still never broke up much cranked , the preamp was too clean. Good day

[@cgavin1]

Great job and a great video! Thanks for sharing.

[@TheBrothaAB]

Thank you!!

[@jzm6403]

I have a mint original 1973 Twin Reverb Master Volume that I converted to a head. Only about 25 hours total on the amp. Absolute Pristine inside. The head has 2- 8" Jensens for practice but sits on a Marshall 2x12 Bottom. One aged Greenback and one V-30. Both made in England. Sweet amp. Both the head and the 2x12 are in Marshall Red Tolex. I had both cabs custom made for me.

[@petedazer3381]

12at7 is your reverb driver or your PI. National made rebranded tubes in the 60’s into the 70’s, mostly sold to service shops. The 470 ohm are your screen resistors. The 1.5k are your grid stoppers. ALWAYS replace your screen resistors on a old amp like that.

[@TheBrothaAB]

Thanks for the info on the Nationals! Can you speak to their quality at all? I wish I knew the history of this amp and where it picked up just one. I'm aware that 12AT7s in Twins are used for the reverb driver and phase inverter. V6 is the PI, and I pulled a 12AT7 from that position. Someone probably moved the 12AT7 reverb driver (V3) to another position to limp the amp along.

[@kbkman7742]

I have seen some nationals imported to Australia. Marked made in hungary but I think they rebranded from all over the place

[@goodun2974]

@@TheBrothaAB , "National" tubes in a *red* box, and with the same logo in red on the tubes themselves, could have been made just about anywhere ---- they didn't make tubes, they merely re-branded them. Country of origin was shall we say "fluid", subject to change, and they may have sometimes changed the printing on the tube to say " Made in Great Britain" or "Made in Germany" to fool people into thinking they were "Mullard" or Telefunken" tubes. Sometimes the tubes were indeed high-quality American or European, but they could also be quality-control rejects, or electronics surplus, but they also rebranded some Japanese tubes as well. Originally, there was a company called National that made radio tubes going back to the late 20's and early 1930's (01A's, 2A3's and 45's and the like) and they made lots of tubes for the military during WWII, but eventually the name got bought and sold a couple of times. Not sure if it was ever the "same" company but there was a National Electronics company that was at one point owned by Richardson Electronics, who made high-quality transmitting tubes, but nothing you'd see in a guitar amp....

[@matthewf1979]

Buy up these 70’s Silverface amps now before people figure out that they’re all great amps with a little work.

[@cgavin1]

They really are a bargain. Just picked up a 72 for $600. I mean wtf. New Made in China crap is 2.5x that much! GL finding a 1972 guitar for $600!

[@matthewf1979]

@@cgavin1 exactly!

[@kbkman7742]

Bought a silverface bassman last year for cheap... it's become one of the best guitar amps I ever had. So easy to work on and tweak. The only complaint I could summon up is that the chassis nuts aren't welded in place.

[@cgavin1]

@@kbkman7742 All the ones I've had have been welded on. I guess over the years that really annoyed a lot of people to the extent it was a common mod. Hehe.

[@goodun2974]

@@kbkman7742 , clean, rough up and degrease the metal around the mounting holes, and clean/rough-up the nuts, and glue the nuts in place with JB Weld epoxy (the slow-cure type, not JB QwikWeld). If you prep the metal well and have good gluing skills, the nuts will stay in place and won't spin when you tighten or loosen the chassis-mounting bolts. I recommend you lightly lube a quad of matching-thread bolts and put them in the nuts to keep the glue from infiltrating the threads while the glue sets.

[@titomartinez9653]

I've got a 72 Super Six Reverb that I MIGHT have re-tolexed. Do y'all do that kind of work? Also, one of the speakers is disconnected, and it's the original speaker, so I'd prefer to salvage it, if possible... It may actually need the whole chassis taken out and looked at. It's getting new tubes, a fuse, and a clean up at Wilcut (in Lexington) right now. I should know more about what all it needs by, the end of the week. Would you be available to work on it, or can you recommend someone else? I don't care to drive to Cincinnati or Louisville, I just want it done right.

[@TheBrothaAB]

Sorry, we don't re-tolex. I'm available to work on it. Send me an email at [e-mail].

[@titomartinez9653]

@@TheBrothaAB Great. Thank you! Do you know anyone who does tolex?

[@randyheath8566]

N I C E

[@TeleStrat335]

I've owned two of these. I consider them the worst sounding of all of the twins.

[@TheBrothaAB]

I am not usually a fan of the silverface twins. I think they maybe do one sound well and the rest seems to come up short.

[@mikerevis6439]

Those wires under the doghouse... dear lord. And you said it looked ok? Um.. no.

[@TheBrothaAB]

I respectfully do not agree with you.