Audio Pro Avantek (B7) subwoofer

[OniJon]

Audio Pro Avantek, B7 plate amp huge power draw on startup. It creates interference to my friends tv, pre-amp and lights. The symptoms are presumably age related, since it is 16 year old amp, any advice?

I've measured it here and there (with Fluke 179) but without ESR meter, cannot say anything about the caps other than that Fluke shows that they have capacitance within tolerance. They're G-Luxon's and Jun Fu's, known BS brands. Should I just yolo this and change all the smaller preamp caps and see what happens?

[OniJon]

Re: Audio Pro Avantek (B7) subwoofer

I got new info about this that could narrow the problem down. If you use power switch manually to power the sub, there is no problems to other devices. Automatic on-off sensing on it interferes with other devices.

[OniJon]

Re: Audio Pro Avantek (B7) subwoofer

Here's some images of the amp if anything comes to anybody's mind

[momaka]

Re: Audio Pro Avantek (B7) subwoofer

Should I just yolo this and change all the smaller preamp caps and see what happens?

At that age, it probably wouldn't be a bad idea, especially if any of the caps were located near warm/hot components. I am just about to post a JBL amp of a similar vintage, and most of its small caps were in quite bad shape.

If you use power switch manually to power the sub, there is no problems to other devices. Automatic on-off sensing on it interferes with other devices.

So it looks more and more like the issue might be related to some of the small caps going bad. Reason I see this is because the smaller caps will be responsible for the pre-amp and main amp biasing. If any of them are bad, that could cause the amp output stage to turn ON instantly rather than gradually and/or connect the speakers to the output stage before it has settled. With that said, do you also hear the speakers connected to this amp "pop" or "bump" in/out when it is turned ON?

Aside from changing the small caps, I also see some tan glue. I can't fully tell if this is the tan glue many of us know here to go brown/black and conductive over time. But if you see any of it has changed color (especially turning darker near hotter parts), then you have that dreaded tan glue. My advice for it: remove as much of it as possible from the board, especially any that's on components' leads.

[OniJon]

Re: Audio Pro Avantek (B7) subwoofer

Those biggest caps (6800uF) were so dry that when you shake them, they rattle. Never seen that before.

[Khron]

Re: Audio Pro Avantek (B7) subwoofer

I've encountered something like that a few times - CapXon and/or some other no-name / crap brand.

Those biggest caps (6800uF) were so dry that when you shake them, they rattle. Never seen that before.