28 Aug
2014
28 Aug
'14
1:19 p.m.
-----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
have 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