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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

wrong logic results
after desoldering the suspected chip
New and old chip

and replacing the chip with a spare did the job.

That was easy...