Clicking Ampeg

[Ted]

I've got a 1966 Ampeg B-15N here.

It clicks occasionally. Seems to be worse when theres a signal present.
All tubes, electrolytics and the mains transformer are new (it did this with the old parts as well)

It seems to be present on both channels. So its either the phase splitter or the output stage. I tried new coupling capacitors, it didn't make a difference.

Any ideas?

cheers
ted

[Ted]

I think its the output transformer.

The amp had previously lost bias because of a failed electrolytic - causing overheating and fuse blowing.

It doesn't sound like the softer "pop" or "rustle" of a noisy resistor. Its a hard "crack" and it only happens when there's a signal present. (and only ocassionally at that). Its not a microphonic effect.

Any comments?

[J Martin]

5{y well be the output transformer arcing. Do you have another transformer you can temporarily connect to verify. Anything close will do. The correct primary is 6600. Anything from 3500 to 8000 will be fine for the brief time it takes to verify.

[Enzo]

I agree, it doesn't have to be close at all, really, all we want is to see if it cracks or not. I keep an old Fender Bassman OT on the bench for exactly this reason. I'll clip it into anything.

[Enzo]

Oh and since it does it on both channels, it is not limited to the PI or output stage, it could also be in the power supply

[Ted]

Stuck in an old 6V6 transformer - sounded terrible but the clicking had gone.
So thats that. Thanks everyone.