DECserver 700 PSU fix, H7881-AA

Gregory Beat w9gb at
Mon Feb 25 12:47:30 CST 2019

Adrian -

ASTEC is now owned by Emerson Power (UK address below).
Emerson Power Catalog (find the 57 watt models):

PowerClinic in Dallas/Fort Worth area 
services a large number of Switch-Mode power supplies.
Power Clinic Inc.
3732 Arapaho Rd
Addison, TX 75001
H7881-AA (Refurbished), $177.00 USD

H7881-AA Power Supply, 57 watt , $450.00 USD

ASTEC - Europe (UK)
Waterfront Business Park
Merry Hill, Dudley
West Midlands, DY5 1LX
United Kingdom
Telephone: +44 (0) 1384 842 211 
Facsimile: +44 (0) 1384 843 355
From: Adrian Graham
To: "General Discussion: On-Topic and Off-Topic Posts"
Subject: DECserver 700 PSU fix, H7881-AA

Hi folks,

My trusty DECserver has bitten the dust in a silent and non-violent way
with the fuse still intact so has anyone got tips on troubleshooting? I
know it's the PSU because I 'borrowed' another PSU from work and the unit
is running again. It's an ASTEC unit under the hood, and in my experience
of fixing the older types like the AC8151 (Memotech, TRS80 II/III, Osborne
etc) the chief culprits on an utterly dead PSU are the input caps and/or
the small 220uF or 330uF startup cap in the feedback circuit.

I haven't checked bitsavers etc for a schematic yet, does such a thing exist? 
Hopefully the ASTEC board has a model number on it.

Owner of Binary Dinosaurs, the UK's biggest private home computer
t: @binarydinosaurs    

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