S5 944B CPU problems

i have this CPU, and i can't communicate with it. there seems to be something wrong with the unit, because the LED configuration is something i've never seen before.

when i power it up, all the LEDs flash, then they ALL go out except the BA light. there is neither a RUN nor a STOP light lit, and i've never seen that before. RESET has no effect. (doesn't look like it tries to reset at all actually, no changes in the lights)

any ideas what is wrong with this CPU? it's one with a Flash Expantion OS module in it.

You said the reset does not work...but have you tried a overall reset? I'm not sure on the 944B, does it have two switches on it? and do you have a GOOD copy of the program?

yeah, tried overall reset, and the stop light flickers once. then nothing. manual says that it's "checking program memory" when run and stop leds are both out, and that a flash after overall reset indicates a memory selftest error.

good program or bad, doesn't matter, i can't communicate to it at all. gives a 'plc timeout' in the software.

i'm proceeding on the assumption that there's a problem with the memory. we've got a replacement isntalled already and we're repairing the bad CPU.

Not sure where you are in NC, but these guys are in the 704 area code and claim to repair S5's http://sterlingservices.com/ if you need someone

Thanks for the advice. among other things here, we do board level industrial electronics repair. we've fixed quite a few S5s, but havn't seen this type of error before, and i needed a few ideas about where to look for the failure in the unit.