[bperboy]

I've received a KLH ASW 10-100 subwoofer from a friend. It doesn't work upon plugin, therefore I opened it up to see what was wrong. There are two circuit boards inside, one of which is partially blackened, and has a charred smell. Obviously it got fried, but I was wondering if there are any schematics out there, or better yet, replacement pcbs available from some repair retailer like Mat Electronics. I will take pictures tomorrow of the circuit board with my macro lens.

 

[balou]

good luck finding replacement pcbs for a specific amp...
but you could probably fix it yourself - either replace some components on the pcb, or rebuild the circuit on a protoboard. can you post hires pics of the charred board?

 

[bperboy]

Quote:

Originally Posted by balou /img/forum/go_quote.gif good luck finding replacement pcbs for a specific amp... but you could probably fix it yourself - either replace some components on the pcb, or rebuild the circuit on a protoboard. can you post hires pics of the charred board?

Yes, I'll do that now.

 

[bperboy]

Pics

First is the board that appears to be fine.

This is the biggest view of the burnt board I could get. The transfrmr is in the way.

Closeup of the most burnt part

 

[Brian_the_King]

Oh snap. Sorry for your loss, hope you can get that fixed with little hassle.

 

[bperboy]

Ideally I could have a schematic to breadboard it off of, but I'm not sure where I'd get one. I did email the manufacturer but I'm not hopeful.

 

[bhjazz]

I'm always amazed at the sloppiness of some of the stuff mfr's think will never be seen. Oy!

I think your best bet is to just pull it apart and replace the components yourself. I've read a few things about that sub, and I don't think there are any replacement boards.

Well, you've got some work ahead. Those two diodes and the large resistor obviously don't look too good. I would venture a guess, by the other shots, that some kind of moisture or water damage occurred. The back of the problem board: the board trace is quite damaged, and the rust definitely screams waterrrrrr!!! It is clear that it caused a short at some point in the life of your sub.

First, take some notes on what is connected between those two boards. Then disconnect them very carfully. A short may exist that connects your finger to whatever is still stored in those capacitors. As the whole thing was plugged into the wall, it could be lethal. I would definitely check all surrounding components. The way the thing died could easily have eaten up multiple parts.

Keep us up on what you find. Looks like a fun project!

 

[MisterX]

You could try contacting KLH and and asking them for a schematic.

http://www.klhaudio.com/contact.htm

Or maybe you could just buy a replacement plate amp from somewhere like apexjr or MCM?

Personally.... Given it is a KLH product I think I would throw it in the dumpster and call it a day.

 

[heatmizer]

Those don't look like diodes they look like thermal fuses. The symbol behind it I believe confirms. The upper main power cap is domed out.

 

[Denim]

Are you talking about ZD3 and ZD4? Aren't those Zenor diodes?

 

[bperboy]

Quote:

Originally Posted by MisterX /img/forum/go_quote.gif You could try contacting KLH and and asking them for a schematic. http://www.klhaudio.com/contact.htm Or maybe you could just buy a replacement plate amp from somewhere like apexjr or MCM? Personally.... Given it is a KLH product I think I would throw it in the dumpster and call it a day.

Yes, I emailed them yesterday, still waiting a response. I got the sub free, so not really any loss.

 

[heatmizer]

Yup my mistake

 

[RedLeader]

heck, even the larger caps on the "good" board look bubbled

 

[bperboy]

Unless KLH sends me a schematic, I think I might be better off waiting until i'm in EE in college and can figure out how to reverse engineer the circuit. I'll keep it as a summer project.

 

[AudioCats]

one quick way to do a retro fix is to get a $10 radioshack "amp deal of the century" and hook it to the woofer speakers. the amp produces 25Wx2 (not sure if you can bridge them, but I suppose paralleling should be ok, so 50W total; if you can somehow bridge the outputs then, theoretically, it can produce 100w output).

But of course with the radioshack amp you don't have the adjustable low-pass crossover circuit, can't help you on that one.