Washburn Bad Dog BD75B

[bsco]

was trying to find a schematic on this but no luck...the amp powered up fine but no sound...there was the usual low thump in the speaker at power up so I assumed the power amp section was fine...but there wasn't even a background noise in the speaker...so after probing around for a couple of minutes I decided to check the rail voltages to the op-amp ic's...and found that the negative supply was pretty much missing...checked some of the associated components around the low voltage regulators and everything checked fine so I gutted the chassis and re-connected everything back up on my bench where it would be easy to get at everything...the problem was with bad solder to the regulators...resoldered and that fixed the problem...and after a good inspection of the boards I found more bad solder connections so I went through everything and then reinstalled everything back in the chassis.....the amp works like a dream now....everything works great......I will still be on the look-out for a schematic and hopefully I might be able to find one....so in the future, when I run into a problem with an amp that powers up with a slight thump in the speaker but no background noise at all, I will check supply rails on the op-amps first before doing anything else...as this was the issue here.....hope this helps somebody out in the future....

[Jon Snell]

There is no schematic for this Chinesium amplifier.
Experience is all you have unfortunately.
Check for dry joints and bad connections.

[bsco]

There is no schematic for this Chinesium amplifier.
Experience is all you have unfortunately.
Check for dry joints and bad connections.

I figured it out after.....got it all working now....it was dry joints on the regulators but had to be completely disassembled in order to repair and check out all the soldering.....Thanks for the tip......my ability to repair stuff without documentation is improving...

[J M Fahey]

I figured it out after.....got it all working now....it was dry joints on the regulators but had to be completely disassembled in order to repair and check out all the soldering.....Thanks for the tip......my ability to repair stuff without documentation is improving...

Welcome to the Club

Way back then I was the one who had to work that way, being in Argentina, no Internet (so no MEF ) and 10000km away from anywhere Hi Tech, no access to Manufacturer´s data, nothing.
Enzo´s famous "CALL them and ask" does not apply here.

But Japanese say about difficult circumstances: "what doesn´t kill you makes you stronger"

But since nowadays everything seems to be made in China, by "mystery Companies", and even "known brand" stuff is actually also made by mystery OEM suppliers, we are all in the same boat.

Oh well.