Fender blackface Vibrolux

[laurie]

Arrrrggghhhh.... EVERY vintage Fender amp just takes so much to get sorted. Put the amp back together and now it is blowing fuses.

Back to the test bench.

So, what changed when I put the amp back together? I connected up the reverb tank. And the (looks like original) 12AT7 driver tube failed

[Pepe]

Argh! So here's the next replacement parts order!

[laurie]

I have a spare drive tube. Now the reverb circuit is feeding back. More fault-finding

[laurie]

It looks like the reverb system failed a long time ago... Both send and receive tubes, some components and it looks like the tank itself are toast.

At least the parts are readily available, but there is less and less "vintage" in this amp every day.

[laurie]

Why is the reverb tank feeding back like crazy... at least the fault is definitive. I wonder how long it has been like this?
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1964 vibrolux reverb tank.jpg (80.64 KiB) Viewed 16114 times

[Pepe]

Please explain. Frankly, I know nothing about reverb tanks.

[laurie]

The reverb springs are on a "carrier" and the carrier is isolated from the main housing with spring suspension. This isolation is necessary to prevent acoustic feedback.

One of the four suspension springs has failed, and the carrier has been jammed up against the bottom of the amp - directly acoustically coupled to the amp wood. Hence massive feedback when reverb is engaged.

I've highlighted the broken spring, and also where the central carrier is actually sitting on a locator pin - the locator pin should be in the middle of the round hole.
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1964 vibrolux reverb tank2.jpg (279.99 KiB) Viewed 16108 times

[Pepe]

Ah, understood. Do you have springs at hand, or do you have to make another order? It is awful having to deal with stuff that others have messed up.

[laurie]

Fix is done. Not perfect, but it works. I reshaped the end of the broken spring. The spare springs in the junk box were all too big/stiff.

Reverb sounds perfect, and amazing.

I'll keep an eye out for spare springs or a dead tank to harvest from, but for now I'm very happy.
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1964 vibrolux reverb tank3.jpg (139.47 KiB) Viewed 16103 times

[Pepe]

So everything works now?