20 Nov
2022
20 Nov
'22
9:03 p.m.
Thanks Antonio,
The location of the diode is arrowed on this picture:
https://rjarratt.files.wordpress.com/2022/11/img_20221120_205802-arrowed.jpg
You can also see the heatsink where the transistor used to be.
Regards
Rob
-----Original Message-----
From: Antonio Carlini via cctalk <cctalk(a)classiccmp.org>
Sent: 20 November 2022 20:38
To: Rob Jarratt via cctalk <cctalk(a)classiccmp.org>
Cc: Antonio Carlini <a.carlini(a)ntlworld.com>
Subject: [cctalk] Re: Identifying a Failed Diode in a Rainbow H7842 Power
Supply
On 20/11/2022 17:40, Rob Jarratt via cctalk wrote:
The H7842 PSU in my Rainbow failed yesterday. At
first the machine
just powered down and there was a slight burning smell, I wasn't next
to the machine when this happened, so I didn't see or hear anything to
tell me where the problem might be. Not being sure if there was a
short in the machine or a problem in the PSU, I disconnected the fans,
FDD and HDD and, probably foolishly, I applied power again to see if the
machine
would work.
At this point there was a bang and a flash in the
PSU.
I blogged this here (it repeats most of that I have said above):
https://robs-old-computers.com/2022/11/20/dec-rainbow-h7842-power-
supp
ly-fai
lure/
I have Rainbow PSUs H7842A, H78420 (which I suspect I may have misread!
...) and H7842D available. I can look tomorrow; if you can supply an overview
picture and maybe circle the location of the offending parts that might help
me identify them more quickly (always assuming that they are marked at all,
of course).
Antonio
--
Antonio Carlini
antonio(a)acarlini.com