Testing Flip Chips

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Over the last couple days we have been trying to track down what else isn't quite right after the magic smoke incident...

The M221 boards had a lot of problems. These are the main registers. On all of them (except bits 0 and 1, that board was fine) E18 was the problem. E18 is a 74H00. These were replaced.

We tried to send characters to MTTTY again but only received NULLs.

Checked pin R1 of M07. This is the trigger that loads data in. This was good with pulses about 500μs apart.

Checked M07U1, which is AC11(1). Something is holding it at low. This is a problem.

Testing Flip Chips:
M706 in M/N06 is good.
M707 in M/N07 is bad.
M707 in M/N10 is bad.
M706 in M/N09 is good.

Warren noticed that one of the ICs on M707 in M/N07 was getting hot. We took the thermal gun to it and it came in aroun 130F. This is a bit too toasty.

We ran the computer for a while and ran the thermal gun up and down the Flip Chips installed in the machine. Nothing seemed out of the ordinary. Average of 75F.

More Flip Chip testing:
M216 in L04 is good. (relay outputs)
M216 in E18 is good.
M121 in E19 is bad.
M216 in E20 is bad. (E18-20 are tape registers)

The M623s found in M14, 15, and 16 are all good.

All 16 G221 cards are good.

As we weren't finding the main case of our problems, we decided to start going down the line starting with Column A.

M222 in A/B22 is bad.
M111 in A35 is bad, a pin is stuck low.
M212 in A38 is bad.
We have no tests for M602 so we couldn't check them.

M121 in C26 is bad.

M617 in D17 is bad.
M113 in D24 is bad.
M304 in D28 is bad.
M113 in D29 is bad. 

Warren has replaced the bad ICs on the M707 cards. Both are 7400s. Replaced E3 on the M216 in E20. 


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