Uit Hack42
(→MM8-EJ) |
|||
| Regel 7: | Regel 7: | ||
| − | a test with our DSlogic analyzer reveiled a broken 7442 on position E59 and replacing the chip with a spare did the job. | + | a test with our DSlogic analyzer reveiled a broken 7442 on position E59 |
| + | |||
| + | [[Bestand:E59 MM8-EJ wrong.png|thumb|400px|links|wrong logic results]] | ||
| + | |||
| + | [[Bestand:Sn7442 los.jpg|thumb|400px|links| after desoldering the suspected chip]] | ||
| + | [[Bestand:Sn7442_swap.jpg|thumb|400px|links|New and old chip]] | ||
| + | and replacing the chip with a spare did the job. | ||
That was easy... | That was easy... | ||
Versie van 20 apr 2015 11:19
Repairlog PDP8/f
Our PDP8/f seems to have problems with its two corestacks. bank 0-3 are taken care of by a Keronics 812075A, a onr board/two slots memory card. Bank 4-5 is a DEC MM8-EJ 8k cardstack of three cards. As we have the docs for the 8k MM8-EJ stack, we started troubleshooting that one first
MM8-EJ
Adresses ending on xxx4 or xxx5 all return zero data, so something is wrong in the adress decoding part or in the stack itself. checking continuity on the X-Y lines of the stack is the first thing to check.
a test with our DSlogic analyzer reveiled a broken 7442 on position E59
and replacing the chip with a spare did the job.
That was easy...