Popping tremolo - dead amp

[überfuzz]

I have a homebrewed amplifier that died on me. The amplifier has a Fender Vibrolux tremolo, i.e. bias wiggling. It was making popping noises when the tremolo foot switch was turned off (possibly also funky when engaged to but not audible). This time it died when I turned the tremolo off. There is a standard hum, that is about the same as before the breakdown. I've done some voltage measurements, albeit rudimentary. So far I haven't found any funky readings.

Two questions. Is there a standard fix for popping vibroluxish tremolos? Any ideas of where I should start looking for the silence issue? (A wild guess is that the last pop did my amplifier in.)

[Jazz P Bass]

You could try removing the Trem tube.

Voltage checks for a dead amp:
Preamp plate & cathode voltages (make sure they are running)
Output tube plate, screen & bias voltages (check at the socket pins)
Output tube pin 8 secure ground on both tubes.

Run a dynamic signal test with a dummy load.
Jump right to the output tube grids. You should see a 50 Vac signal with all controls cranked.

That leaves the OT.

Get the amp running & then the Tremelo circuit.

vibrolux_6g11.pdf

[überfuzz]

Okay, now I'm really dumbfounded. I take the amplifier home, put it on on my bench and it works!? I did pull all tubes while transporting, and now I can't find any wonky tube in the set...

Anything I should control before I call it okay?


I feel like sorting the spikes coming out of the tremolo circuit.

[überfuzz]

The anode voltage is ~400 Vdc in my oscillator. Is that excessive?

[überfuzz]

Did you have a suggestion on how to smooth out the spikes I get while disengaging/engaging the tremolo..?

[überfuzz]

No one with any suggestions? I'm not skilled enough to figure out what to try. :-/

[Jazz P Bass]

Did you have a suggestion on how to smooth out the spikes I get while disengaging/engaging the tremolo..?

You could help by telling where the spikes are, circuit wise.

Are they reaching the Intensity control?

The footswitch turns the low frequency oscillator on & off.
So, I would scope the 0.1 coupling cap, both sides.

[überfuzz]

You could help by telling where the spikes are, circuit wise.

Are they reaching the Intensity control?

The footswitch turns the low frequency oscillator on & off.
So, I would scope the 0.1 coupling cap, both sides.

Actually I don't have a oscilloscope available now. However, I toyed with the idea of helping the low-pass filter formed by the intensity pot and the .05 uF capacitor. It seems to me that the spikes are getting worse if the pot is in high position, intensity high. Do you think an added low-pass filter on the bias wire would smooth the spiking coming from the oscillator..?