Date   : Fri, 22 Jul 2005 00:36:46 +0100
From   : Mike Tomlinson <mike@...>
Subject: Re: floppy discs

In article <005b01c58e46$41eaf7e0$c91e4e51@...>, Colin
<cwhill@...> writes

>Where (roughly) is C9?

Take the PSU out (3 screws), and turn it upside down so that you're
looking at the insides.  Orientate it so that the mains input cable is
pointing away from you and the low-voltage output cables are nearest to
you.

Look towards the back of the PSU.  You'll see a large, silver transistor
(about the diameter of a 10p piece, though about four times as thick)
mounted vertically on a piece of metal - the heatsink.  C9 is to the
immediate south-west of that transistor/heatsink assembly.

Just a word of warning - switching power supplies can retain a
potentially lethal charge for long periods of time after being
disconnected from the mains.  They are supposed to contain bleed
resistors to dissipate any residual charge but bitter experience tells
me these don't always work as expected.  

Be very careful working around switching power supplies, particularly if
you are inexperienced or you have, or suspect you have, a weak heart.
This applies especially to Master power supplies, where the
bleed/startup resistors tend to go open, leaving a nice charge of ~330v
sitting indefinitely in the mains smoother capacitors, just waiting to
give your bits a good stir.  I've had really nasty shocks from Master
power supplies which have been sitting in boxes for two weeks awaiting
return to Acorn under warranty.

M.