Processor card for a HP 9835.

Paul Berger paul.h.berger at
Fri Oct 16 13:59:06 CDT 2015

Hi Rik,

I am pretty sure it is the CPU, the key had fallen out of the monitor 
cable and I accidentally plugged it in backwards, and when I turned it I 
almost immediately noticed the smell of magic smoke escaping.  The +12V 
regulator was wrecked, both the 723 and its pass transistor plus a 
couple burned foil traces on the power supply board.  I have repaired 
the power supply and all the voltages are good now,  the clock input to 
the CPU is good, however the clock outputs are dead.  I also fear for 
the ROMs in the machine but I can fix that as I had already designed a 
ROM card for option ROMs that I could easily modify for the system ROMs.


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