KLIPSCH KSW-10 amplifier

[-goodtimes-]

Hello,

I have a Klipsch sub amp that needs repair. It may be the rectifier, some (what appear to be) FET's and resistors. Here are some pictures to get started. Any guidance will be greatly appreciated!

[particleman]

Re: KLIPSCH KSW-10 amplifier

Whats wrong with it, Missing channel , stuck in protection?

[mariushm]

Re: KLIPSCH KSW-10 amplifier

First thing one normally does is checking voltages.

You have that AC input with center tap in the middle (that will be the ground), the bridge rectifier converts that to DC and then you should have two regulators (the to-220 ICs in picture 2, bottom left corner.. probably 78xx and 79xx)

That area looks quite hot, which may point to some kind of short there. Check the bridge rectifier to make sure it works fine (use diode check on a multimeter), check the resistors to make sure they're not shorted or faulty, check the two voltage regulators to make sure there's proper voltages on their outputs.
It could also be that one of those two zener diodes are faulty (right below those two ICs).

It would be best to scrape away that yellowish glue between those resistors and the ICs - sometimes that glue becomes conductive and causes shorts.

The Q4 IC (the one to the right of that voltage requlation section) looks burnt/damaged - you can see that the text on it got discolored from the heat. It's possible that one is shorted.
It looks to me like the same IC that's further to the right, and that one's a TL074CN which is a quad opamp.
If this opamp is shorted, it could draw too much current from the voltage regulation section which in turn could overheat that area and cause the regulators to not output proper voltages.
Download the datasheet for that chip ( https://cdn.badcaps-static.com/pdfs/...fa29e05014.pdf ) and measure for short between Vcc+ and Vcc- , the center pins on each side, and then with the board powered up measure the voltage.

Get back to us with some info and we'll go from there.

[-goodtimes-]

Re: KLIPSCH KSW-10 amplifier

Hey guys! I am really cramped for time with all this holiday stuff and have not had a chance (until now) to check anything out or reply. I will do my best to check all of the things you mentioned and get back asap! The amp does nothing but start to get hot around the dark areas if you plug it in and power it up. The resistors get hot almost immediately and I just turned it off quickly after feeling that. Something is definitely out of whack! Thanks for the quick replies!! I am just getting into this stuff on the next level from changing fuses, cleaning switches and pots, recognizing and changing bad capacitors and so on. It really interests me and I enjoy fixing and understanding this stuff.

So, Cheers!!!

[dank4]

Re: KLIPSCH KSW-10 amplifier

First thing one normally does is checking voltages.

You have that AC input with center tap in the middle (that will be the ground), the bridge rectifier converts that to DC and then you should have two regulators (the to-220 ICs in picture 2, bottom left corner.. probably 78xx and 79xx)

That area looks quite hot, which may point to some kind of short there. Check the bridge rectifier to make sure it works fine (use diode check on a multimeter), check the resistors to make sure they're not shorted or faulty, check the two voltage regulators to make sure there's proper voltages on their outputs.
It could also be that one of those two zener diodes are faulty (right below those two ICs).

It would be best to scrape away that yellowish glue between those resistors and the ICs - sometimes that glue becomes conductive and causes shorts.

The Q4 IC (the one to the right of that voltage requlation section) looks burnt/damaged - you can see that the text on it got discolored from the heat. It's possible that one is shorted.
It looks to me like the same IC that's further to the right, and that one's a TL074CN which is a quad opamp.
If this opamp is shorted, it could draw too much current from the voltage regulation section which in turn could overheat that area and cause the regulators to not output proper voltages.
Download the datasheet for that chip ( https://cdn.badcaps-static.com/pdfs/...fa29e05014.pdf ) and measure for short between Vcc+ and Vcc- , the center pins on each side, and then with the board powered up measure the voltage.

Get back to us with some info and we'll go from there.

Hi , there.
i have the same problem , and my PCB looks the same , it look like it was burnt at same place.
so i would follow your advice in order to find out where the problem is..
can you please note where should i check the bridge rectifier ? where to test it with the probes?i checked the diodes - with the diode test at the fluke , and one shows 0.72V on one polarity and infin on the other , while the second one shows 0.72V on one polarity and aprox. 2.1V on the other.the opamp IC is not shortened.

what do you suggest will be the next step ?

many thanks

[HemiRick]

Re: KLIPSCH KSW-10 amplifier

The 1st diode measures good and the 2nd is bad. I know that much....but thats all I can contribute.

[dank4]

Re: KLIPSCH KSW-10 amplifier

i have also tested the zener diodes while with power. found -14.8V on D4 and 15.23V on D5..

[budm]

Re: KLIPSCH KSW-10 amplifier

Any components that are tested on board and show bad or strange reading you should then remove and test them again off the board.

[dank4]

Re: KLIPSCH KSW-10 amplifier

how would i know which zener diodes to find (i mean what is the PN) ,
or may be it does not matter ?

Thanks for the help

[dank4]

Re: KLIPSCH KSW-10 amplifier

adding few low res pictures of my board , as you can see there are burn signs at the input stage - however i suspect that one of the output transistors is the cause - since i found it shortened - which could explain overloading the input stage.
i will try to replace the output transistors and will update..

but still would be happy to hear any suggestions or insights.

thanks.

[budm]

Re: KLIPSCH KSW-10 amplifier

Pictures are way out of focus for my eyes to see what are on the boards.
We also need the pictures of the bottom side of the boards.
Since your boards are the same as in post 1, I will use pictures in post one as guide.
Those two TO-220 case devices are transistors, NPN and PNP set up as simple +/- Linear regulators with base set Vref to about 15VDC by the Zener Diode for the OP-AMP.
You can use 15V 1/2W so the output at the Emitter of the Transistor will be about 14.4V.
or you can use 15.6V 1/2W so the output will be 15V.
They use the power resistors to drop the Voltage down to feed those two linear regulator circuits which is a bad idea and wasted lots of power in heat, they should have use another low Voltage winding on the power transformer for the +/- supplies instead of using the high Voltage supply for the power amplifiers to drop the Voltage down to +/-15VDC or so.
BTW, what is the problem are you having?
-14.8V and +15.23V are not going to stop the op-amp from functioning, Zener diodes do have tolerance, 5% is typical which what you are getting is within the range.

[dank4]

Re: KLIPSCH KSW-10 amplifier

Just so i get this right , after the bridge we have approx ±30V and they are dropping about 15V on the resistors so the input to the Transistors stage would be ~ ±15V ?

the problem i have is that the SUB doesnt output any sound at all , yet the green(?) led on the panel does turn on when i switch it on , another symptom is that the aoudissy system at my marantz does not recognize the sub-woofer when it is connected .

might you have a basic schematic of such electrical design ? i am not sure i got it all by reading your description.

thanks again

[emmanhello]

Re: KLIPSCH KSW-10 amplifier

Hi, I know this post is old but I've got the same issue and I did some reverse engineering so I thought I would share knowledge:





My conclusion is bad caps. 47uF ones (C35, C36, C37, C38). I couldn't get the part number of the transistor/mosfets but my guess's the caps smooth the voltage ripple at the gates. Since their capacitance is lowered because they're old, the mosfet's ripple increase and cause them to heat.
I will validate this theory tomorrow when I change these 4 caps.

[budm]

Re: KLIPSCH KSW-10 amplifier

Sorry, but your schematic is wrong.
Please see the correct way to make series positive linear regulator using NPN pass transistor.
https://cdn.badcaps-static.com/pdfs/...3da308ff49.pdf

Same topology for Negative, just have to get the PNP for pass transistor.
http://www.bristolwatch.com/ele/zener_power_supply.htm

[emmanhello]

Re: KLIPSCH KSW-10 amplifier

Thanks for correcting me, it's the first time I see such topology of power regulator.
Yeah my circuit is probably wrong, I forgot to mention I didn't check at the transistors orientation and parts number. Also diodes are actually ~15V zener.

I changed cap, it's working so far. I don't think that fixed the source of the issue since the transistor zone is still warming up, specially on the negative side. At least my subwoofer is now consistently working. (For how long?)

Here's the hopefully fixed schematic:

[budm]

Re: KLIPSCH KSW-10 amplifier

That is better.
C36 should be flipped around so positive pin is GND.
They waste lots of power on those 430/520 Ohms resistors that is why the board gets so hot and cooks the caps. They should add another transformer winding or two taps to the winding for the low Voltage to run the OP AMP's.

[atheod]

Re: KLIPSCH KSW-10 amplifier

Hey guys,

thanks for sharing info here regarding klipsch ksw-10 sub.

Exactly same picture of burnt area for my ksw-10.

Has anyone managed to find (recreate) the complete schematic of thus sub?

As for me I found the 3300uF caps are shorted. Could be the glue as one suggested above. I will try to replace the caps anyway.

Regards

[duke2k]

Re: KLIPSCH KSW-10 amplifier

Hello,
I have a KSW-10 sub. When I got it the light would come on but no sound. Checked the power supply section for voltages and I am getting 43V on both rails. Checked the voltage for the opamps, getting 14.6V on both rails. Found bad caps (C35, C36, C37, C38). Replaced the caps and still no sound started checking for shorted transistors. Found one Q3. Replaced Q3, Now I have output but the volume is low. Checked the volume pot and it was reading 85K on pin 1-3. Changed the pot and still low volume. Does anyone have the schematic or service manual for a KSW-10? Any ideas?
Thanks

[duke2k]

Re: KLIPSCH KSW-10 amplifier

Ok, found the problem C12 50V 1uF. It was reading 160pF. Wow huge difference in volume. Damn bad caps

[brad1dado]

Re: KLIPSCH KSW-10 amplifier

Does anyone know if I can buy a replacement power supply for the KSW-10 without having to buy the Bash 300S (power supply & amp circuit assembly)? I'm wondering what type of power supply would work. (Toroidal?)