128k Mac Schematic needed

From: Paul Braun <nerdware_at_laidbak.com>
Date: Mon Oct 19 23:33:51 1998

Date sent: Sun, 18 Oct 1998 19:24:46 +0100 (BST)
Send reply to: classiccmp_at_u.washington.edu
From: ard_at_p850ug1.demon.co.uk (Tony Duell)
To: "Discussion re-collecting of classic computers" <classiccmp_at_u.washington.edu>
Subject: Re: 128k Mac Schematic needed


<<SNIP>>

> Anyway, to get back the other original problem. Sounds like the PSU is
> tripping. The Mac+ PSU (and the 128 one is similar, I think) is horrible.
> It has to have the right dummy loads on both the 5V line and the 12V line
> for it to power up. IT takes the regulation sense voltage from the 12V
> line. And the chopper heatsink is live (don't ask...).
>
> But my first reaction would be to test (using an ESR meter) or replace
> all the electrolytics in the PSU section (lower half of the analogue
> board, below the connector that goes to the logic board), especially
> those near the logic board connector.
>
> -tony

Thanks. I'll fire up the Ungar and start swapping. I shoulda thought of that -- I
know old electrolytics can go bad, especially in less-than-ideal storage. My
guess is that they were on the edge when I got it, and that one time was
enough to weaken them to the point of failure.





Paul Braun
NerdWare -- The History of the PC and the Nerds who brought it to you.
nerdware_at_laidbak.com
www.laidbak.com/nerdware
Received on Mon Oct 19 1998 - 23:33:51 BST