PARITY ERROR on 6300 (might be power supply)

[Bill Mayhew]

A while back, I started having problems with my Xerox 6064 machine,
which is aa functional identical clone of the PC6300, built on the
same Olivetti chassis.  The only oddity of the Xerox 606x series is
that they had verison 1.36 ROMs, where were 1.43 minus the EGA
support.  A call to the AT&T parts hotline (1-800-222-PART) got
me 1.43 ROMs for about $35 (US).  If anaybody needs the com code,
drop me a line; when I ordered, they knew whata it was without the
com code.

Well on to the real subject.  My machine has the LB series power
supply.  There are LA and LB supplies.  Around December 1989, my
machine started crashing every 20 minutes just like clockwork.
Occascionally it would die with a partiy error, usually on my Intel
Aboveboard, but occasionally the system board.  Other times the
machine would just lock up.

A while back we received a service bulletin that mentioned that the
connectors for the four pin disk drive on the power pack tended to
develop cracks in the solder.  I disassmbled the power supply and
resoldered the drive connectors to the PC board.  No dice.  I still
got the crashes.  Finaally, I decided, "what the heck", and
resoldered every joint on both the pc boards in the supply.  After
I did that, I've had no more spurious crashes since January.  There
weren't any obviously bad joints that looks like cold joints on
either of the two boards, but re-flowing them did the trick. 

Don't mess with the internal parts of your power supply unless you
know what you are doing.  There is the possibility that incorect
reassembly could cause a short circuit.  There are high voltages
inside the supply, so you should allow several minutes for residual
charges to disipate before working on the power supply.  Obviously,
you should never attach the supply to a wall outlet with the cover
ov the power supply removed.  The supply will also not function
correctly unless the output loads are connected.


==Bill==
-- 
Bill Mayhew  Northeastern Ohio Universities College of Medicine
Rootstown, OH  44272-9995  USA    phone: 216-325-2511
wtm at uhura.neoucom.edu   ....!uunet!aablue!neoucom!wtm
via internet: (140.220.001.001)