On 2/13/19 1:43 AM, Fritz Mueller via cctalk wrote:
SUCCESS!!
Put the M795 out on an extender, loaded 167777 in RKBAR, and had a look around
with a logic probe. Narrowed it down to E34 (a 7430 8-input NAND). Pulled,
socketed, replaced, and off she goes!
I can now successfully boot and run both V6 Unix and RSTS/E V06C from disk.
*THAT* was a really fun and rewarding hunt :-) First message in the thread was
back on Dec 30, 2018. Lots of debugging and failed DRAM repairs, then the
final long assault to this single, failed gate...
Thanks to all here for the help and resources, and particular shout-outs for
Noel and Paul who gave generously of their time and attention working through
the densest bits, both on and off the list.
I predict a long happy weekend and a big power bill at the end of the month :-)
cheers,
--FritzM.
Congratulations. Well Done.
I am trying to understand how the diagnostics didn't reveal this
defect. I see in the source for the diagnostic DZRKH-F there are tests
for address in the 28K-32K range and also for the 32K boundary.
I'm trying to make sense of the M795 to get a better understanding. Any
addition data on how the 7430 failed (input bad, output bad, etc ?)
Jerry
