Take a close look at each electrolytic capacitor. Those are the large, black, cylindrical ones. ... not the small, ceramic ones. They are prone to failure when they age. It is difficult to tell visually if one of them is bad. The only sure way is desolder each one and test it. ... Any sign of leakage, maybe a discoloration next to the capacitor would be a clue, but the only sure way is to desolder and check.
Checking usually requires a capacitance measuring meter.
...

I have looked at those 100 times. They are not leaking or discolored at all. I have a meter with uF capacitor check. What should the reading be? And what exactly do the capacitors do? I mean I know they store energy. But let's say one fails in general, what are the symptoms? I can tell you that the main transistors all had 50 volts at the C pins. I used an IR temp gun all over the board for any hot spots. Nothing over 80 deg. But I also have to have a connection unplugged to get the unit to even stay on. So it wasn't trying to drive any output I'm sure. That's the only way I can bypass protection mode and keep the unit powered up.

 

... Different things can happen . Electrolytic capacitors sometimes are placed alongside voltage regulators to even out any ripple voltage following conversion from AC to DC in the bridge rectifier section. If the capacitor shorts out, then DC current goes directly to ground.
... If that has occurred in your circuit, then check a few of the capacitors around the voltage regulator part that looks burned.

 

... Different things can happen . Electrolytic capacitors sometimes are placed alongside voltage regulators to even out any ripple voltage following conversion from AC to DC in the bridge rectifier section. If the capacitor shorts out, then DC current goes directly to ground.
... If that has occurred in your circuit, then check a few of the capacitors around the voltage regulator part that looks burned.

There are small caps by the 2 voltage regulators. It's easy enough to desolder them and check. I guess I probably better.

 

... Note that all electrolytic capacitors are polarized, which means that they will have a distinguishing negative mark someplace on the case ... (-). This negative mark must always be installed with the same orientation that it had when it was removed. ... Make some kind of mark next to each capacitor before you remove it, something that can't be erased or smudged out. It might be a good idea to draw a sketch showing all the electrolytic capacitors and their polarity orientation, as well as capacitance.

 

It was hard to tell from the pictures whether it was glare but I noticed some white discoloration that is indicative of liquid damage. Look the board over carefully and remove any "stains" with isopropyl alcohol, 70% or better without additives using a Qtip swab. Dust can be removed with a soft brush or DRY canned air. Also, look closely for any cracked solder joints and resolder if needed. Before removing anything, take pictures. Electrolytic caps are marked for Voltage, Capacitance, and Temperature. Replace with like-kind if needed.

 

It was hard to tell from the pictures whether it was glare but I noticed some white discoloration that is indicative of liquid damage. Look the board over carefully and remove any "stains" with isopropyl alcohol, 70% or better without additives using a Qtip swab. Dust can be removed with a soft brush or DRY canned air. Also, look closely for any cracked solder joints and resolder if needed. Before removing anything, take pictures. Electrolytic caps are marked for Voltage, Capacitance, and Temperature. Replace with like-kind if needed.

I marked the position. It reads 6349 uF. The cap says 6800. Good?

 

That's less than 10% so not too bad...

 

I would strongly advise contacting KLH to obtain a circuit diagram if available. The new owner doesn't have much online but here is the contact page: Contact KLH Audio | Best Home Theater Speakers

 

That's less than 10% so not too bad...

The other is 6361. But....the cap says negative is black. And the caps black terminal was not on the negative track on the board.......

 

The cap on the left had black neg terminal in the hole to the right with the black ground wire you can see. The cap on the right hand the silver terminal in the left hole where the ground wire is. That ain't right!!??

 

They should have been installed like this

 

That cap goes straight to the failed transistor to. It's plain as day

 

OK, now we really need a circuit diagram. Because, for negative voltage smoothing the electrolytic plus IS on the relative ground rail! Put it back like it was or it will likely blow. The KEY is the stripe down the side of the can that indicates negative, not the base terminals. I am NOT an audio expert! There are different requirements for capacitors for noise suppression in audio systems that I do not know the requirements for.

 

If the cap was in backwards it would have blown up! The system would have NEVER worked.

 

OK, now we really need a circuit diagram. Because, for negative voltage smoothing the electrolytic plus IS on the relative ground rail! Put it back like it was or it will likely blow. The KEY is the stripe down the side of the can that indicates negative, not the base terminals. I am NOT an audio expert! There are different requirements for capacitors for noise suppression in audio systems that I do not know the requirements for.

The stripe goes down the side to the black terminal on both. It says negative. And the middle holes on the board are negative. For sure. The ground wire lead comes off it and goes to the chassis. And the resistor that was blown goes right to that same track as the capacitor terminal in question. That can't be right

 

It's a dead short to ground. Just like that resistor acted when it burned up.

 

Did it ever work?

 

Did it ever work?

Have no clue. I've never seen it do anything but start resistors on fire.

 

Aha! Contact KLH for the circuit diagram. In the meantime, if possible, can you measure the voltage to see if it is + or - ? Time for me to go, getting late...

 

Aha! Contact KLH for the circuit diagram. In the meantime, if possible, can you measure the voltage to see if it is + or - ? Time for me to go, getting late...

I already did. It shows negative reading on ohm meter it I put positive lead on the negatives of caps. And it shows positive voltage . 2vdc if you put the leads on the correct polarity terminals . So it's not like they are charged backwards