16 Dec
2006
16 Dec
'06
9:20 a.m.
It looks clean and great, but it reports CDAL parity error (machine check
10) randomly if the panel head is installed in place, when it is processing
bulk of data. If the panal head is hanging there loosely, the chance of
getting a CDAL parity error is much much rarer.
What could cause this problem? A defective cache memory chip? supportive TTL
chip? capacitors?
Or is it better for me to unsolder the CPU and sell it to collectors?
Any idea?
vax, 9000
16 Dec
16 Dec
10:37 a.m.
New subject: What to do with a VAX KA655 board that is prone to CDAL parity error?
9000 VAX wrote:
It looks clean and great, but it reports CDAL parity
error (machine check
10) randomly if the panel head is installed in place, when it is processing
bulk of data. If the panal head is hanging there loosely, the chance of
getting a CDAL parity error is much much rarer.
What could cause this problem? A defective cache memory chip? supportive
TTL
chip? capacitors?
Or is it better for me to unsolder the CPU and sell it to collectors?
Any idea?
That's a bit odd. What is this "panel head" of which you speak? The
thing with the sockets on?
I'd wonder if there was some crazy earthing shenanigans going on.
Gordon
17 Dec
17 Dec
5 p.m.
On 12/16/06, Gordon JC Pearce <gordon at gjcp.net> wrote:
That's a bit odd. What is this "panel head" of which you speak? The
thing with the sockets on?
It is the metal cover with several switches, an 7 segment diagnostic LED and
the console serial port socket.
I'd wonder if there was some crazy earthing shenanigans going on.
I swap in another KA655 and that one works perfectly, even with the panel
head that I talked about. So I guess something happend to the first KA655 so
it is sensitive to noise. I decide to take it off duty.
vax, 9000
Gordon
20 Dec
20 Dec
1:28 p.m.
Well, I thought there might be loosing solder on board. So I baked the KA655
in a oven, slowly turn up the temperature, peaked to 450F till the solder
melt. Then I let it cool down slowly.
This time it failed self test #31. I thought it was beyond my ability to
repair, so I heated the board on stove and picked the big chips off the
board with a pair of chopsticks (it is easy for those chips with heat
sinks). I think many of you do not get a chance to peek the bellies of those
chips, so I post the photo on my website. You can find it here,
http://www.mscpscsi.com/PHOTOS/KA655_chips.jpg
Five square chips other than the 78332 CVAX are belly up.
vax, 9000
6420
days inactive
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