TOA A-903MK2 Protect Mode

[mnfreelancer]

Hey all - I'm at a hotel property right now and half the room won't work because the TOA A-903MK2 amp is stuck in protect mode. I have power cycled the amp a number of times with no result. I'm not ready to pull it out of the rack and tear into it yet - anybody have these amps and have any suggestions? The event tonight can easily limp along with just half the room working - the other half is mostly dead space for projection. Thanks.

[museav]

Have you tried disconnecting inputs and outputs? There may be something causing it to go into protect mode and if that is not addressed then power cycling the amp will not do anything. Also, make sure that all the input cards are properly seated and that the speakers are wired to the proper terminals and have the 4 Ohm/25V/70V or 8 Ohm/Direct switch properly set (the A-903 is different than the A-906 and A-912), any of these could be causing the amp to go into protect mode.

[mnfreelancer]

The tech that worked the shift before I showed up said that he disconnected the bridging input/output on the problematic amp and the protect light went off after a power cycle. This was the first thing I tried but the protect light remained on. I proceeded to disconnect all inputs, then the output terminals, isolating the amp, cycled power and the light remained on. The manual (operating manual) mentions a thermal mode so I'm thinking that the thermocouple / hi-limit switch may be faulty. I'll probably pull it out and look into it on Sunday.

[museav]

I've seen a number of TOA A-900 and P-900 series products go into protect mode do to improper output wiring or switch positions, which is why I suggested checking that first. I did have one unit that went into protect and stayed there like it sounds yours is. Unfortunately, that was some years ago and while I recall that it was thermal related, I don't remeber what the specific problem was.