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FDP Forum / Fender Amps: Vintage (before 1985) / 74 Fender Twin Reverb



Jan 10th, 2018 03:57 PM   Edit   Profile  

I looked at a 74 Twin Reverb the other day but it lacked power (I know I owned a 74 before). I see it had the original tubes in it. I know that could be the problem that and 100 different things. Has anyone here on this forum cleared that problem up by putting in new tubes? Thanks Keith

Contributing Member

American Patriot

About as ordinary as you can get.
Jan 10th, 2018 05:39 PM   Edit   Profile  

Tubes might be the first thing to try if volume was low. Oh, I would test the tubes too.

Contributing Member

So. Cal. USA

Jan 11th, 2018 09:50 AM   Edit   Profile  

Make sure the speakers are wired correctly and the speaker cable is plugged into the main out not the extension jack.

No telling but if it were on my bench my first look would be to check the filter caps for high ESR to ensure it is actually safe to operate then check the bias setting on the power tubes.

Knowing the current draw will tell you what is up with the power tubes. If it passed all this then it's time to look at the phase inverter and preamp sections.

Roger Ball
Contributing Member


New guitars, old amps. Perfect.
Jan 11th, 2018 11:03 AM   Edit   Profile  

All the above advice is spot on.

I discovered something while doing a full maintenance on a friend's 1970 Twin Reverb, including tubes, filter caps, cleaning pots etc. The amp sounded OK but I thought it should have been louder. Just before putting it back together I poked around the board with a wooden chopstick while strumming. Somewhere around the phase inverter area the thing suddenly jumped up in volume. I could also make it go quieter again indicating a poor solder joint somewhere.

I re-flowed the connections in the general area and that solved it. Just lucky, but you never know.

These amps are workhorses but years of being played, dragged around and loaded into trunks and trailers can take a toll on electrical connections.


usa metro detroit

Jan 27th, 2018 03:58 PM   Edit   Profile  

Waiting to get my 75 Twin Reverb back from the tech. I had it black faced and it sounded awesome, then during a gig went dead. Turns out the OT trans fried. After 40+ years well isn't that a kick in the arse! lol how dare that Twin!

IMo I really like an early 70's Silver Faced Twin that has been blackfaced. I use the Master volume and think that it doesn't suck the life out of the amp's tone at all. The extra gain feature of the amp well... now that is an epic fail, but I never use it.


usa metro detroit

May 27th, 2018 06:51 PM   Edit   Profile  

Turns out it wasn't the OT, but a bad bias pot. The old Tech couldn't find it. I sent it to a different tech who found it. Pretty rare he said. The new tech said it was when the amp heated up it cause the bias pot to short out throwing the bias wacko. Thinks probably from some cleaner years before.

Does this guy know his stuff? OMG! the guy went through and was measuring resistors for to much drift and changing them.

Said the amp wasn't quite right as far as schematics go and correct the changes made by the original tech. Between a new OT and the specialist going over it, the amp is practically brand new.

FDP Forum / Fender Amps: Vintage (before 1985) / 74 Fender Twin Reverb

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