SWR Basic Black issue

[Hatcher]

Hi All

I really hope someone out there can help me out. I have a SWR Basic Black Combo which has an issue. When I plug in it sounds fine for about a minute then it sounds warbly (if that makes sense) almost like a distorted tremelo. Alas SWR sold to Fender and there seems to be zero support these days.

I am pretty good with circuit boards to component level but really don't want to desolder each component to find out which one is defective.

I tried different cable, different guitar, both active and passive inputs, external speaker and just about everything else. I did notice the high power resister which looks after the horn was not connected both ends so did put that back on in the hope that was the issue. It was not.

There is a Chinese 12AX7 on the circuit board which lights up but I have no means of testing it.

Anyone have ANY clues at all?

Cheers



Andy

[BassBod]

Can't help, but any experienced amp tech should be able to sort it out - very standard 80's tech. Look on the web for a circuit plan, as that always helps. The amp is probably at least 15 years old so a number of components could be out of condition etc etc.

[paul_5]

If you don't mind having a look at the guts yourself then an audio probe is dead easy to make, and should help to identify the problem area on the board. Even if it's something you can't fix yourself, then you could at least tell the technician where the fault is and save them a few hours' work (and yourself a few quid).

[Roland Rock]

I'm not sure that it's the same thing, but I had a SWR Basic Black and it started to make an odd noise. This was twelve years ago, but if IIRC the noise was like a kind of quiet, slow-decaying metallic echo/reverb with each note.
The diagnosis was that a coil had gone on the driver, and a replacement driver sorted it out.