Fender blackface Vibrolux

[laurie]

The resistor and nearby wiring all overheated. And the tube socket

[Pepe]

So that all happened after your extensive overhaul?

[laurie]

So that all happened after your extensive overhaul?

No. I hadn't got to that part of the testing and checks yet. Every one of these I've done has been an iterative process. Fix the obvious stuff then chase down the next thing.

[laurie]

Parts arrived last week. Replaced the three octal sockets and surrounding resistors with measured and matched components. Everything is now working apart from the vibrato. I have the parts for that and will tackle it next.
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Vibrolux failed socket pin.jpg (230.95 KiB) Viewed 107477 times

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Vibrolux new socket.jpg (150.89 KiB) Viewed 107477 times

[laurie]

Bought some of these for the amp. They sound amazing.

https://www.tubeampdoctor.com/en/6l6gcm ... ected?c=76
https://www.tubeampdoctor.com/en/gz34-s ... m-selected

[laurie]

Finished. The vibrato had three problems:

• One of the 100k resistors (on the back of the speed pot) had a dry joint.

• The 0.02uF capacitor was out of spec - 0.027uF.

• The optocoupler assembly (the "roach") had failed.

Lots of fun chasing all that down, but done now.
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1964 vibrolux.jpg (217.09 KiB) Viewed 106646 times

[Pepe]

Very good!

The "vibrato" is a tremolo, correct? And is it in the chain before or after the reverb? I'm still baffled that it is reverb -> tremolo in the case of the BOSS FDR-1.

[laurie]

Total work done:

• Cleaned. And cleaned and cleaned.

• Replaced the 2-prong power cord, removed the "service outlet", removed the "death cap" and associated switch.

• Changed the fuse holder to a modern safe holder.

• Replaced the 10k resistors in the doghouse.

• Replaced all the 25uF electrolytics.

• Replaced the three octal sockets plus the screen and grid resistors. Replaced burned cloth-covered wires in the heater supply circuit.

• Replaced the 0.02uF cap in the vibrato, plus the opto "roach".

• Changed the 0.047µF cap in the vibrato channel tone stack to a 0.022µF (same as the Super reverb).

• Fixed a ding in the speaker baffle.

• Replaced the output tubes plus rectifier tube with TAD red-base tubes. Set bias to 43mA.

• Use heat to reform one of the knobs that had been hit.

• Straightened the chassis behind the front panel (had been hit on the vibrato controls).

[laurie]

Very good!

The "vibrato" is a tremolo, correct? And is it in the chain before or after the reverb? I'm still baffled that it is reverb -> tremolo in the case of the BOSS FDR-1.

Well... yeah. I'm using the name Fender gives it.

Vibrato (tremolo) is after the reverb.

[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.