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After my Fender Pro Tube Twin has been on for about a half hour I’m getting a loud high pitched noise coming from the Reverb?

I checked Tubes & replaced one but the noise is still happening.. The rest appear to be good.. I had them all changed all of them this past year or so..

Lots on YouTube’s about buzz but this isn’t a buzz.. It’s a high frequency hum…

If I turn off the Reverb it stops..

Any ideas what it is & what to do?

Thanks

i believe that uses a real reverb tank along the bottom, yes? if so, check the cables running to and from it. massage the ends a bit, and if they unplug easily (RCA cables like the older Twins?) then make sure they are clean enough and well connected.
the tank and wiring can be sensitive to RF interference, maybe even computer screens and such if not in good shape.

High pitch squeal? That can be caused by oscillation. Maybe something like this:

https://www.youtube.com/watch?v=V29BctjcqQk

Not sure if it's the same on the 'Pro Tube' line but Silverface/Blackface Twins gave the reverb driver tube a hell of a hard time.

Looks to be V7 in the Pro Tube versions so the socket layout is different.

The answer was to always use a NOS JAN tube (Phillips / GE) in this slot - 12AT7WC JAN Philips. It needs to be a hardy and non-microphonic tube otherwise the reverb can and will squeal like a nonmusical banshee at inopportune times.

Thanks for the info.. I’ll try all of them tomorrow..

I did use a wood Chop Stick & tapped all the tubes.. The only one that was bad was the V8. I replaced it.. That didn’t stop the noisy Reverb..

Feb. 2023 I had all the Tubes replaced & Biased.. $408.00! This Amp has 12 Tubes..

I bought the Amp new in 2013 & has been in for repairs 4-5 times over the years.. This is my least used Amp. My other Amps that I use all the time have no issues.. Could be the problem?

Anyhow, Thanks! I’ll let you know how it works out..

I put a little De Oxit on the 1/4 inch Jacks. I plugged & unplugged several times.

I payed for a half hour. Then put on Standby for a half hour. Came back & played another half hour. It seems to be ok now.

So, a new V8 tube & Jack & Input cleaning may be all it needed.

I’ll be doing a Recording Session tonight. Hope it’s all good.

Thanks

I was going to say sounds like a bad tube. Great you got it sorted out.

Larsongs wrote: ↑

Tue Apr 02, 2024 12:56 pm

I put a little De Oxit on the 1/4 inch Jacks. I plugged & unplugged several times.

I payed for a half hour. Then put on Standby for a half hour. Came back & played another half hour. It seems to be ok now.

So, a new V8 tube & Jack & Input cleaning may be all it needed.

I’ll be doing a Recording Session tonight. Hope it’s all good.

Thanks

oh good! hopefully that is all. i've often found that going over those connections will even make a functioning reverb circuit sound a lot better.

Reverb tank feedback is usually from two things IME...

The driver tube (12AT7 in V3 on most Fenders) is bad/microphonic

Or the tank and bag are screwed down too tight causing the tank to vibrate/resonate with the cabinet. The metal chassis of modern tanks are a little thinner than the old ones so they vibrate more. You should be able to move the tank around a bit with your hands, you don't want it clamped down too tight.

The Amp made it through the Recording Session without any problems! Yea!

The V-3 Tube seemed fine. I did replace the V-8 Tube as it was Microphonic.

I’m going to check the Screws on the Tank & loosen them if they’re tight..

Thanks everyone

Rock on!

Reverb driver is V7 in those amps.

Possibly just re-seating the connections and verifying the reverb cables were securely connected to the proper locations was your solution.

I've definitely noticed some strange behaviors resulting from dodgy or erroneously-connected reverb tank cable interconnects

I had a silverface Twin, that had the orange JBLs in (important bit of information) that would, randomly during playing even at relatively low volume levels, suddenly blast a high frequency SCREAM of feedback at MAXIMUM VOLUME that only went away by turning it off. Like, every frequency from 3khz-20khz all at the same time.

Twins are loud. SF twins are louder. SF Twins with JBLs are even louder than that.... Imagine sitting 4 or 5 feet away happily noodling around some dreamy post rock nonsense or whatever at home and then get "Back to the Future"d with no warning. Fuck that amp.

øøøøøøø wrote: ↑

Wed Apr 03, 2024 6:21 pm

Possibly just re-seating the connections and verifying the reverb cables were securely connected to the proper locations was your solution.

I've definitely noticed some strange behaviors resulting from dodgy or erroneously-connected reverb tank cable interconnects

That seemed to fix the problem.. It’s working fine. There was another Tube that needed replacing. Which I did.

You guys saved me from having to load that 85 lb. beast into my Chev Silverado Pickup & hauling to my Amp repair guy.. Which is no easy task as my Truck sits pretty high off the ground!