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FDP Forum / Amp Mods, Repairs, and Projects / Trying to repair Fender Hot Rods and various re-issues 2


New York

Jun 6th, 2019 08:43 PM   Edit   Profile  

I'm trying to repair a Twin Reverb RI.The reverb was not working. The pan and cables checked OK. V2, V3 and V4 have been replaced. Reverb transformer has also been replaced.

The reverb jacks were separated from the circuit board and various mods were done by the previous tech to the jacks and other portions of the reverb circuit. I believe I restored everything to their original states.In the case of the reverb jacks,I had to connect the green transformer wire directly to the "inner" white jack, and the black wire to the "outer" white jack, which gave me connectivity from the black wire to the ground side of R26,C15 and R27.I had to jumper from the red jack to both sides of R26. When I first checked the jack, there was connectivity between the inner and outer jacks, which I undid.

I did the test where you plug a guitar into the red reverb jack and heard guitar coming out the speaker, so the reverb recovery circuit checks out. I did the reverb driver test and plugged a guitar into the vibrato channel, and plugged the white reverb jack to the speaker, nothing. After some checking I found R25 did not connect to ground.The previous tech put a big gob of something all over R25 but I was able to jumper from R25 to the ground side of C14. Now I heard some guitar coming out the speaker. But it sounds very noisy and trebly, and the reverb does too.

Just for comparison I took a working Twin and plugged a guitar into the red jack. NO SOUND! Hooked it back up to its reverb pan and nice lush reverb. Now I'm getting confused. I take out a Deluxe Reverb and both driver and recovery tests work. Why didn't the tests work on the working Twin? And what should I be checking to resolve a noisy and trebly reverb?

Contributing Member

Planet Peegoo

Rhythm & Lewd Guitarist
Jun 7th, 2019 04:38 AM   Edit   Profile  

Sounds to me like that amp was goofed with because it developed a problem in the reverb, and the tech did a bit of a bodge on it. The bright/trebly symptom you describe may be due to an open ground.

FDP Forum / Amp Mods, Repairs, and Projects / Trying to repair Fender Hot Rods and various re-issues 2

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