Whitechapel MG-1 : dead power supply ?

From: Jules Richardson <julesrichardsonuk_at_yahoo.co.uk>
Date: Wed Jan 14 19:57:59 2004

On Thu, 2004-01-15 at 01:03, Tony Duell wrote:

> Not according to the totally lusing service manual that came with my XXX
> (it has a glossary which includes :
>
> IC : Integrated Circuit. One of those black things on legs on a circuit
> board [1]
>
> ICs : More than 1 IC

Ooh, it does too! Ha ha!

> How are you supposed to 'bypass the PSU'?

Their words, not mine :-) The relevant bit with the crappy flowchart is
page 5-3, which then refers to a Technical Information Notice for the
bypass routine. (I don't *think* I have any of those notices)

Looking at the block diagram for the PSU (pg. 4-3) I'm guessing shorting
across the switched relay contacts so that it's always on would do it;
the service processor should start up and the battery should get the
appropriate charge voltage.

Presumably power-down via the touch switch should work then too.

Whether the machine will power up normally in this state I don't know;
the block diagram implies that it should though as power-up logic for
the machine as a whole is only handled when the service processor sees
proper mains-derived regulated voltages from the PSU, not the +5V from a
healthy battery. (Invalid NVRAM at that point is another matter, but
nothing that fitting the workshop ROM to bypass the key disc security
shouldn't fix :-)

cheers

Jules
Received on Wed Jan 14 2004 - 19:57:59 GMT