AB International 9220 amp latch up issues

[The Rebel]

I know this isn't a common amp to work on, but I am grasping at straws for a heads up on doing a latch test on the left channel on my amp. Typical story where it was working fine the last time it was played, then go to put it back in the system and the left channel is shooting sparks off the speaker wires when tying to connect them.
The only service manual I can find is for the 9220A amp, which according to the schematic has a different board layout than the 9220 does. The first thing in the service manual is a latch test when the amp develops over +/- 3V. This amp has a THERMOEFFICIENT mode switch that when is not activated, makes the amp just go in and out of protection mode. The amp will power up if you activate the switch. I'm getting -15V to -6.3V DC voltage out of the left channel, the right channel still works , offset voltage is around 50mV in the right channel.
From what I am reading in the service manual, the latch test will bring it out of latch up when it's done properly. Is there anyone in here that has had any time working on AB amps with this problem?

I can't post pics of the schematic, so I'll link to the service manual for the 9220A that shows the latch test. Compare that PCB to my PCB. I'm lost.


https://www.hifiengine.com/manual_library/ab-international/9220.shtml

 

[laatsch55]

What brand amp is this??

 

[laatsch55]

Never mind, I see it..

 

[The Rebel]

AB International 9220 Professional Series. The only service manual I have found so far lists it for the 9220A. Here is the Latch test procedure in the manual that is supposed to release it from latch mode if that's the issue with the amp. It calls for applying DC current through a 10k resistor across two points at R74 and R75. My PCB doesn't have either of those points.

 

[laatsch55]

All that is telling you is when you test the DC circuit protect and trigger it,you can unlatch the triad by turning off the amp and bleeding the power supply caps. In your case you have not fixed the problem of DC on the outputs, therefore you can not untrigger the triac....

 

[The Rebel]

I'm guessing this is what you would do after you find and repair the DC issue on the left channel output? Would performing this test not return the amp to normal operating status per statement #3 in the steps above? I'm trying my best to learn how amp protection circuits work, what puts them into protection, and what would cause DC at the outputs. I'm almost thinking this was caused by a speaker issue, or a connection flub when he was hooking the amp up after storing it.

 

[laatsch55]

There are quite a few things on those driver boards that can put DC on the outputs.
No, doing the test will not reset the trial if the DC is still present...