Re: IIGS CPU: Failed its self-test; what next?

[JJeffries@psu.edu (Jason Jeffries)]

In article <D3pMo9.60F@presby.edu> sebugg@presby.edu (Stephen Buggie) writes:

>       FAILED SELF-TEST:  I activated the internal self-test (both Apple
>keys held down at power-up).  It goes through the early phases of the self-
>test; then, when it gets to the flashing characters, it does not proceed
>any further.  The sound test (ascending tones) happens, but SYSTEM GOOD
>_fails to appear_.   Thus, there is a fault in the motherboard.

>       BTW, the testing was done with no interface cards plugged in,
>so don't blame the performance on interface cards.  I used a IIC monitor
>while doing the test.

>       Only three of the ICs are socketed: the CPU, a ROM chip beside it,
>and a large long IC near the keyboard end.   I removed each of the three
>socketed ICs; no change.

I think the "long ic near the keyboard end" you describe is the Ensoniq. 
That wouldn't cause this problem.

>WHAT SHOULD I CHECK NEXT?  Could it be a bad 65c816 chip, or one of the
>other two socketed ICs?  How risky would it be to a good IC to try
>swapping with ICs from a perfect IIgs?

It does sound like the processor is bad; I've had plenty of experiance with 
non-working processors (snicker). The question is: If that's so, what killed 
it? What I would try first is taking the processor that we believe to be 
dead and putting it in a known-working GS system. If that GS still works, 
the processor is fine, and we may suspect other components on the GS. If 
not, time to call Alltech... I think that might be better that risking your 
other GS's CPU in a possibly unfriendly system. I doubt that even a severely 
damaged processor could damage the GS you use to test it.