Kicker ZX700.5

[S Merlington]

I noticed C239 vented in this amp..

When hooked up all it does it make the speaker flutter out of all channels?

Does this indicate there is another problem somewhere ?

Wondering what might cause this to vent

 

[Perry Babin]

What's the DC voltage across pins 4 and 8 of U127?

 

[S Merlington]

Black probe on pin 4 red probe on pin 8 -11.37

 

[Perry Babin]

When papaZBill gets here, he can take over. Until then...

Black probe on negative speaker terminal.

Voltage on pin4?

Voltage on pin 8?

 

[S Merlington]

Pin 4:-42.4

Pin 8:-54.3

 

[Perry Babin]

Was the amp working and just quit?

Has any work been done to it?

 

[S Merlington]

No work has been done to the amp ..

My friend said it was working and just quit on him

 

[Perry Babin]

Are you sure that you don't have pins 4 and 8 backwards?

I don't know how you could possibly get the power supply reverse polarized for that IC. The reverse polarity could cause the cap to fail but the Zener would have to open as well and that's not likely with the resistor that's in series with it.

 

[S Merlington]

With the black probe on the speakers ground terminal here's what I get on the pins ..

Pin 4:-54.3
Pin 8:-42.4

The diode tests fine

The resistor reads 2.2k in the board

 

[Perry Babin]

That's reversed from what you previously posted.

I don't know what could have caused the cap to fail. Replace it and check the function of the amp.

 

[PapaZBill]

U127 is a KIA393, btw. Pin 4 is tied to the negative rail and Pin 8 is tied to the cathode of the 12v zener D231, so these voltages are correct.

 

[S Merlington]

I can get the sub channel to work I can also get 2 out of the 4 channels to work ..

The other 2 channels for amp 2 have no output at all..

Any ideas where to go from here ?

 

[PapaZBill]

Check front, rear and sub channel inputs separately, and post results.

Check all four signals from the preamp board, white connectors near x/over switches. The white wires carry the signal and on the board they are labeled R-L, R-R,F-L,F-R. and then to the main board.

 

[S Merlington]

Ok back to this amp..

On amp 1 inputs from rca ground shield to negative speaker terminal I get 0.2 ohms ..

On amp 2 and also the sub input from rca shield ground to negative speaker terminal I get no reading meter stays at OL..

Should I get a reading on all of the RCA shield grounds to negative speaker terminal?

Reason I ask is because both channels (amp2) have a high pitch squealing on the outputs. The sub channel plays but sounds like you are in a wind tunnel also ..

 

[PapaZBill]

Amp 1 must have an input to properly work. Your readings are normal.This is the reason you have a squeal and poor quality on sub channel.

If you aren't getting good audio from all channels, you may have bad RCA'S. You can check this with an ohmmeter. With out signal applied test the contacts from the back side of all RCA'S. They should all be a dead short.