16 May
2007
16 May
'07
10:23 a.m.
Pierre Gebhardt <cheri-post at web.de> wrote:
my first VAX ever - died, unfortunately. During the
last months, I experienced that the CPU just got stuck at some time, but I could not
reproduce this error.
Sometimes, it froze during or directly after the initialisation procedure, or later on
after half an hour or an hour of work with VMS.
A friend of mine thought of instable voltages caused by the power supply, so I swapped it
with another one in order to check, if the supply was to blame.
But it wasn't the case. I took out all the boards and left the CPU and some memory
only, but it didn't get any better. After getting stuck, the CPU could only be reset
switching the supply off and on again.
And now, since last week, the CPU doesn't come up at all anymore. After switching on
the power supply, the seven segment display shows an "F",
nothing is printed on the terminal, and the halt-button has no function anymore (which
was always the case when it got stuck). So I guess that my VAX died...
Needless to say that these boards can't be repaired. As far as I know, no schematics
were ever published and these big chips on the board are horrible to unsolder and solder,
even
if spare ones could be obtained (supposed that one knows, where the "problem
is").
What you write is "not inconsistent" with failing to get DCOK from the
power supplies. DCOK is a signal indicating that the power supplies
are all up and operating. The CPU refuses to even begin its self test
until DCOK is asserted.
BA213's (a popular cabinet for your CPU) have two supplies and the light
has to be on on both of them. Otherwise you see exactly the symptom
you have (CPU stuck at "F").
It's not impossible for a CPU board to fail and get stuck at "F", but
in my experience, 99 times out of 100 it's because there's no DCOK on the
backplane. And 9 times out of 10 it's because the power supply is
failing. They often go flaky and are hard to start, or go flaky and
fail after getting warm, etc.
It's also true that the power supplies need a certain minimum load...
you may have had some boards in your backplane that had nothing except
for resistors on them to provide the minimum load. Putting those
back in won't hurt. Of course, spare KDA50 sets are just fine for
sucking up DC power too!
Tim.