23 Feb
2009
23 Feb
'09
2:27 a.m.
Hi
Sounds like capacitors.
Alhough it's a switcher any high voltage/high value capacitors in the
PSU might well need reforming.
Quite often you will see caps with a pair if incised lines on top. This
makes them go pop instead of bang.
You would not want to see a PSU where they have gone bang.
Rod Smallwood
The DEC Collector
-----Original Message-----
From: cctech-bounces at classiccmp.org
[mailto:cctech-bounces at classiccmp.org] On Behalf Of Robert Jarratt
Sent: 21 February 2009 19:17
To: 'General Discussion: On-Topic and Off-Topic Posts'
Subject: RE: Powering up a 20-year old MicroVAX II
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Robert Jarratt
Sent: 20 February 2009 22:45
To: cctalk at classiccmp.org
Subject: Powering up a 20-year old MicroVAX II
I have just collected a MicroVAX II which has been in storage and has
not been powered on for 20 years. This is my first machine of such an
age, unfortunately I am not particularly knowledgeable at the
electronics level (I studied circuits academically 25+ years ago and
can solder a bit, but that is as far as it goes). I know I will need
to treat it carefully in order to get it working again. I plan to open
it up and make sure I clear out any debris etc, but
beyond that I need
advice from those with the experience and knowledge
that I lack on how
to go about powering it up carefully.
Thanks
Rob
After removing all the boards and leaving just the disk and tape drive
for load I impetuously decided to try powering it up. I knew the PSU
(model
H7864) was set for 110V and made the switch to 240V (I am in the UK).
When I connected the power cord, after a few moments there was a loud
pop, followed by another before I could pull out the power cord, smoke
rose from the PSU.
This sounded just like when I had once accidentally made a 110/240
mix-up.
The question is, could it be that I had not made the switch to 240
correctly, or could this just be down to the age of the PSU?
Regards
Rob