Clarion DPX11500 #2 Repair

[Zeptoplix]

I was advised to start a new thread for this amp.

I acquired another damaged DPX11500.

First things first, this board is in way better condition than the last... While still not functioning, it became clear that this one was the better choice to concentrate on.

Using a headlight to limit current I tested the amp. It powered up, but when into protect with the protect light blinking rapidly in sets of three.

Research lead me to this possibly being an internal short, I tested the outputs while installed and didn't like the values of one. (much different then the othes) After pulling all the outputs (2SA1294 and 2SC3263) the protect light no longer came on. Tracing back through the circuit i did not find any dead shorts. I haven't tested any ICs. Unfortunately I do not have access to a scope.

With the transistors removed, I had 1.2VDC on the speaker output.

After reinstalling the transistors, (new) I have 1.2VDC (usually falls to .98 or so) on speaker out.

I did a quick audio test, and there is output, however it is distorted; you can tell what is playing but its not usable.

I tested resistors, transistors, and diodes back to some IC's but stopped there. Any idea where I should be focus?

[Perry Babin]

Which terminals of the defective output transistor were shorted together?

[Zeptoplix]

Sorry, I should have clarified.

Once they were pulled from the board, they all appeared to be ok. I installed new, strictly because I had new ones here. Diode test between pin one and two read 538, as did pins 1 and 3. When I test two and three, i get no reading.

Also, I found out from the previous owner, that when the amp failed it was a sudden failure at turn on, and it pulled the subs all the way in.

I tested the PWM IC, and it appears to be ok. I didn't get any low readings, they were comparable and I mean near identical to the brand new one I installed in a different amp.

[Zeptoplix]

Ok,

I bought a better DMM, since the one I had been using previously. When I do a diode test, or a resistance test, it doesn't seem to hunt anymore for a reading..

I'm still trying to hunt down the source of some DC voltage and distorted output. There were a couple of diodes that were suspect, but after pulling them, they appeared to be ok.

This amp will power on and produce output, rotating any of the pots doesn't make a difference.

I've been advised to replace the gate resistors on the outputs. They appear to test ok, and I'd rather not throw any more parts at the amp without having a solid idea to focus on.

I've been reading the service manual and reviewing diagrams. It is fairly easy to find by googling "DPX11500 service manual"

Any ideas?

Thank you

[Perry Babin]

Do you have positive and negative regulated voltage on the power supply pins of all of the op-amps?

Do you have both positive and negative rail voltage on the center legs of the output transistors?

What is the DC Voltage on pins 1 and 7 of U2?

[Zeptoplix]

Hi Perry,

I will check. Where should I be grounding to?

[Zeptoplix]

Ok, grounding to the negative terminal block I get:

+25V on each 2A1294 centre pin
-25V on each 2SC3263 centre pin

U2 I get

Pin 1: 9.2VDC
Pin 7: -9.2VDC

[Zeptoplix]

Sorry, I can I not edit my own posts here?

U2 is an NE5322P

[Perry Babin]

Do you have audio on R36?

[Zeptoplix]

I do not have a scope, will I be able to detect that with my DMM? I have an Extech Dm220.

I get 42mv DC on R36