Polk Audio PA880

[S Merlington]

Got another one of theese in for repair..

2 of the filter caps were vented , a 180 ohm resistor was burnt in the remote wire circuit and a 100 ohm resistor that goes to pin 8 was burnt..

Replaced all of thoose..

What would cause the new filtr caps to vent again within 5 secs??

Also i have 0.00 volts on all pins of the 494 besides pin 16 which is at 4.41 volts


Any ideas?

 

[Perry Babin]

Unless the capacitors were installed with reverse polarity, you need to provide a bit more information (primary or secondary filter caps, photo of the board...).

 

[S Merlington]

Theese are the 2 caps that vent..

 

[Perry Babin]

If you essentially have 0v on all pins of the 494, the power supply could not have been in operation so the only possible problem wold be the incorrect installation of the capacitors. I'm assuming that the capacitors are rated for at least 16v.

 

[S Merlington]

They are 2200uf 25 volt caps..

The amp powerd up for a min before the caps blew for the 2nd time..

 

[Perry Babin]

Are they in the circuit before or after the yellow filter inductor?

 

[S Merlington]

Before..

I will try installing 2 new ones and see what happens

 

[Perry Babin]

Power the amp up with them out of the circuit and confirm that you have 12v on the pad that you believe is the positive pad.

 

[S Merlington]

Replaced the caps ..

Amp still has 0.00 volts on all pins of the 494 expect pin 16 that is at 4.41 volts

 

[Perry Babin]

Did they blow again?

Did you have them installed correctly before?

 

[S Merlington]

They didnt blow this time.. I put them in the same way this time as last time..

 

[S Merlington]

I found a 1N5232B diode to be defective in the remote wire line..

Is there a good sub for that since i dont have one on hand ?

 

[Perry Babin]

It's a 5.6v Zener. A 5.6v Zener in the 1N4700 series would work as well.