Memphis PRX1.1500

[cajones65]

Hi guys,
I have this Memphis on the operating table. The symptoms are protection light and power light are both on. I pulled the outputs to see if protection light would go off, nope. I pulled driver board, no help there either. Pulled the power supply FET's, that wasn't the answer. Has anyone ran across this before?

 

[Perry Babin]

Is pin 16 of the 494 going high driving it into protect?

 

[cajones65]

It was high, 12v. Now I have a dead amp. I was probing and lost both lights. Looking for that problem now.

 

[cajones65]

Found that problem, shorted a transistor in remote circuit, a marking M6 (Q17)

 

[Perry Babin]

So, where are we, now?

 

[cajones65]

Trying to find a replacement for the M6 2sa812, that I don't have on hand.

 

[Perry Babin]

Use an MMBTA56 for now.

 

[cajones65]

Thank you, that worked great. Now back to the original problem. I have 12v on pin 16 causing the shutdown.

 

[Perry Babin]

Can you post a photo of the control area showing all of the transistors in high enough quality so that I can read the circuit board designations?

 

[cajones65]

I think so

 

[Perry Babin]

Lift Q23, and Q50, one at a time to see which allows the amp to come out of protect mode.

http://www.bcae1.com/temp/SLA1500.pdf

 

[cajones65]

Perry 23 lifted allows amp to turn on.

 

[Perry Babin]

Check Q49.

 

[cajones65]

I checked it, it has a 4.7ohm resistor across the base and emitter. I pulled and checked it anyways. It checked good, I replaced it anyway.

 

[Perry Babin]

Try Q10.

 

[cajones65]

Perry I found Q09 open, its in the output section, next to the 5 regulator (U9) and diode D17. Amp is on, fixing to drop a cap in the FET's location and check to see if all is well in the power supply. Thank you.