KSW-300

[bscloutier]

I have a KSW-300 subwoofer that has served me well for quite some time. Recently it was disabled by a lightening strike. I lost a lot of equipment and very litte of it has been completely fried. I think this subwoofer is salvageable.

I am temped of course to upgrade to some other bad boy like the RT-12d or something. The issue is the insurance. Just about anything that I purchase would be an upgrade since I wouldn't settle for less but the insurance only covers "replacement". I fear that I am going to be forced to repair this KSW-300. I wouldn't mind that specifically since it has been a respectable member of the audio team in here. If I upgrade they may only agree to cut me a check for the depreciated purchase price. That won't net much.

The box powers up (red LED on) and the fuse does not blow. It, however, remains on even if you move the switch to off. There is no response to audio nor any deflection of the cone when the plug is inserted/removed from the wall. I haven't tried all of the inputs.

Since the surround receiver had to be replaced with a Pioneer Elite VSX-21TXH which I can argue is a direct replacement for the prior Elite unit, I am assuming that the damage to the subwoofer was caused by the charge through the LFE input. It probably fried the circuit right in that vicinity which also involves the auto power-on detect I assume.

Do any of you know if there are schematics available? Would there be
replacement boards available? I can handle the component level repair
but would rather be spared the reverse engineering if support is
readily available. I suppose I could purchase another used KSW-300 if I
find one and make one good one out of the two

Any advice? Experience with insurance companies and audio replacements?

[bscloutier]

Just to close this out for those of you who might take an interest...

Klipsch was very helpful and passed me the appropriate service manual which basically is a short overview of the circuits, a bill of materials and the schematics.

The +/- 12V supplies are at the main amp board and they were functional after the lightening strike. The control board has series resistors in line with the supplies and I could tell that the control board was in trouble and loading the supplies. The board has 6 AN6551 opamps on it and it was easy to see just from the odd way the turn on circuit was behaving that at least one of those was disabled. I replaced all 6 thanks to Mouser with KA4558. The AN6551 are hard to find and a bit pricy with those who have a few trying to capitalize. The KA4558 are equivalents for like 60 cents.

With the new opamps the board was still not functional. I then proceeded with a blanket replacement of all the caps. I'll plug Digi-Key for that.

After replacing the capacitors the subwoofer would power off and on automatically in response to audio signal but still would not boom. I noted that flipping the phase switch generated a sutible deflection in the cone and that the main amplifier seemed anxious to move some air. So why wasn't signal getting through? There was obviously signal through to the audio detect and power on stage. There was obviously signal from the phase inverted opamp through to the power amp. In between there is a high pass filter which is supposed to roll off below 20Hz followed by an odd transistor-based diode clamp followed by a tunable low pass filter. There was no signal after the high pass filter. In face the output of that stage was clamped.

So while the capacitors for that high pass stage were correct and I replaced them with the corect values the two related resistor did not match the schematics. Are these tuned by hand? Was there a production deviation? I don't know but R1 was 7.5K instead of 14K and R19 was 619K instead of 240K. The replacement opamps must have just enough different in input offset current to put that 619K out of the stable operating range. Replacing those resistance with the proper ones (or, um, what I had that was real close) got me back up and shaking the house.

It's just interesting. Did you non-electrical engineering types out there follow this? Fun. Other than my wife who appreciates that I didn't drop the $2,200 for the RT-12d or the insurance company who gets away with covering a couple of lowly parts invoices, no one cares. But I have the low end back and I care!

Thanks for the help Klipsch with that manual.

[TheEAR]

Always protect your electronic gear with a quality power bar/conditioner.I have lost gear in the past due to a mishap when the electric company was doing repairs and ZAP. Since then I have it all protected ,bills saved and insurance, pictures(and owners of the stores where I buy that can reprint the bills and validate my claims).

You should at least get the value of the fried gear and add the extra to get what you want. Insurance companies have many clauses and hidden BS, just to give the least possible. Know what is yours and claim it.

[mustangdaren]

I was wondering if I could get a copy of the service manual for the KSW 300 from you. Klipsch is not being very helpful and just wants me to send it to their service center to be repaired for far more than what a new amplifier cost.