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FDP Forum / Fender Amps: Vintage (before 1985) / '72 Twin Reverb SF tube rattling!



Sep 10th, 2019 05:34 PM   Edit   Profile  

They rattle only once the tubes are fully heated, when I play certain low frequency notes at a volume higher than I’d say 4 on the master and 7 on the volume.

I know its the tubes, I can press upward with a toothpick on the tube that's rattling and it will stop. Or grab the sides of the tube with an oven mitt.

However, this is where it gets weird. It’s only ever one tube that is rattling. But it will change if I take out 2 tubes (one being a tube that rattles). So say the middle left tube is rattling, I’ll take out the middle 2 tubes, turn it back on, wait for it to heat up, and then the left most tube will rattle.

I tried taking off the metal “bear trap” things that hold the tube steady to no avail.

What could be the problem here?? The amp sounds amazing otherwise, loud and crisp. Just that awful glassy rattle.

Edit: It's the Power Tubes btw not the Preamp tubes.

(This message was last edited by rattlintubes at 07:38 PM, Sep 10th, 2019)

Contributing Member

American Patriot

About as ordinary as you can get.
Sep 10th, 2019 09:14 PM   Edit   Profile  

Sounds like a tube socket issue to me. If you can "wiggle" the tube and the rattle stops, it may not be a faulty tube but the tube socket.
Do you know how to tighten up a tube socket?

Contributing Member

Midwest USA

Sep 11th, 2019 02:03 PM   Edit   Profile  

Don't go sticking a small metal screwdrive in the rectifier or power tube sockets without discharging the caps. 500vDC awaits you.



Sep 11th, 2019 02:11 PM   Edit   Profile  

I think I may have figured out the problem. When I take a tube out, the tube socket will move very slightly if I touch it, as if it is not secured to the metal bracket holding it in.
I think I'll try using some heat resistant adhesive to hold them in place, rather than get new ones as I don't have the money to have someone replace them or the expertise to do it myself.
But if this doesn't solve it, I'll just take it into a shop.

Contributing Member

If irritation occurs

discontinue use.
Sep 11th, 2019 03:21 PM   Edit   Profile  

Each tube socket on that amp is held in place with a pair of screws. Can you operate a screwdriver? If so:

Unplug the amp and flip it on its head on a carpeted floor. Gently remove the tubes and keep them in order so you know how they go back in.

Apply a tiny dot (less than a drop) of blue Loctite to the side of each screw head so the Loctite flows around the head of the screw. Gently loosen the screw one turn only; this allows the adhesive to flow under the head. Snug the screw down.

Gently reinstall the tubes and it's ready to go. No need to wait for the Loctite to cure.

WARNING: do not stick anything into the tube sockets except for the tubes themselves, and keep your fingers away from the metal pins as the tubes are coming out and going in. Even unplugged, an amp can deliver a lethal jolt.

FDP Forum / Fender Amps: Vintage (before 1985) / '72 Twin Reverb SF tube rattling!

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