New Zealand Vintage Computer Forums

Yes, piggybacking doesn't always identify a faulty RAM chip. It depends what the fault within the RAM chip actually is. If piggybacking works a faulty RAM chip has been identified but the converse doesn't apply. The chip could still be faulty.

It's such as easy thing to do though, it's always worth a go if RAM is suspected.

Code: Select all

THE PINOUT FOR THE PET PARALLEL USER PORT

                                 1  1  1
      1  2  3  4  5  6  7  8  9  0  1  2
      =  =  =  =  =  =  =  =  =  =  =  =
     ### ######################### ######
      =  =  =  =  =  =  =  =  =  =  =  =
      A  B  C  D  E  F  H  J  K  L  M  N

   1 - System Ground        A - GND
   2 - TV Video             B - CA1
   3 - IEEE-SRQ             C - PB0
   4 - IEEE-EOI             D - PB1
   5 - Diagnostic Sense     E - PB2
   6 - Cass.1 Read          F - PB3
   7 - Cass.2 Read          H - PB4
   8 - Diag Tape Wrt.       J - PB5
   9 - TV Vertical          K - PB6
  10 - TV Horizontal        L - PB7
  11 - GND                  M - PA2 (CB2)
  12 - GND                  N - GND


Looks like H-Sync and V-Sync and Video signal are available at the User Port, doesn't this mean I can wire up one of my RGB monitors ? I'm willing to give it a go its TTL level so its safe.

How you getting on with this???? Still want some old mother boards?