SWR Workingmans 15" humming

[BassCrazi]

I have a SWR Workingmans 15" bass amp which has an irritating transformer sounding hum. The hum occurs when I switch the amp on and turn up the volume, even a little way, with or without any cables or instrument connected. The hum volume esculates as the volume is increased. The hum would appear to be from the pre-amp because it exists at the sound desk as well when connected via XLR cable from the XLR - DI out on the amp. I mailed Fender support about it (Fender now own SWR) and the response from them was simply: "That is correct, when you turn up the volume you will hear a hum...". Not very impressive, I must say! Is there a solution to this problem, beyond seeking assistance from the product owner...?

[Enzo]

Well, there is always some amount of hum, and Fender most likely thought that was what you refered to.

If hum is excessive, then I;d explore the input jack and the solder connections to it. I'd make sure all the nuts on the controls were tight, and on the jacks.

I would check the output pins of each op amp to see if DC was sitting there.

I would scope stage by stage to se where the hum was getting in to the signal path.

[BassCrazi]

SWR Workingmans 15" humming

Thanks Enzo, appreciate the feedback. I will post an update when I get it sorted.

Cheers

[danmagruder]

Workingman 15" hum

I work on the SWR 750X quite a bit and thhey will display a hum that is present without anything plugged in to them. This hum is caused by the contacts at the input jack (it is a stacked dual 1/4") springing open and not grounding properly. I am not sure which jacks the working man has but it is a not so obvious spot to check when tracing the signal flow. Good luck.