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Old 8th Dec 2020, 7:33 pm   #143
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 10,842
Default Re: I found it! A very sorry looking MK14.

Check list:

1) Visual inspection, no cut-off component leads curled over and getting to know each other on the track side of the PCB? (The sort of thing which could happen after the PCB has been pressed down on a few times).

2) Check the regulated supply voltage if not already done.

3) Remove and check all ICs for possible folded-over pins. While doing so, use your IC tester to re-check all the TTL (except the 7445 which it does not seem to do correctly)

4) Try all possible combinations of two of the four RAMs in the 'standard' RAM sockets, which on the issue VI are the two closest to the PROMs.

5) Try your other PROMs

6) Try another SC/MP.
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