28 Aug
2014
28 Aug
'14
3:22 p.m.
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
On Behalf Of Robert Jarratt
Sent: 28 August 2014 21:19
To: 'General Discussion: On-Topic and Off-Topic Posts'
Subject: RE: Mysterious rtVAX 1000 Failure
have
-----Original Message-----
From: cctalk-bounces at classiccmp.org
[mailto:cctalk-bounces at classiccmp.org]
On Behalf Of Matt Burke
Sent: 28 August 2014 20:07
To: cctalk at classiccmp.org
Subject: Re: Mysterious rtVAX 1000 Failure
On 28/08/2014 18:53, Robert Jarratt wrote:
devices
There are two outputs from the PSU that I
don't fully understand,
one is P OK, I am guessing that means *something* is OK, but not
sure what, power perhaps, but what power?. The other is called LTC,
I have no idea what that one means. Can anyone enlighten me?
'P OK' is indeed power OK. This signal will be asserted once all the
power supply outputs have reached their normal operating voltage. The
Qbus will be held in reset until this signal is
asserted.
'LTC' is the mains derived line time clock (50hz here in the UK).
Have any of the internal fuses (or circuit breakers) blown? Don't
replace
then
until you find the real problem. I would probably
start by checking
the
bridge
rectifier and main switching transistor for
shorts.
Matt
I can't find any fuses. There is a circuit breaker, but it doesn't seem to
tripped (it would be sticking out, right?). I notice
that the light in
power switch
comes on when I turn it on, if it was the fuse/circuit
breaker, I expect
even the
switch's light would not come on.
There are a number of candidates for the main switching transistor, I
think.
Is there a printset somewhere? I have never been able
to find one, and it
would
help in identifying components.
Regards
Rob
Just tested the rectifier, while in-circuit, and it appears to be fine, no
shorts anyway.
Regards
Rob