Date   : Thu, 16 Feb 2006 04:55:54 +0000
From   : Mike Tomlinson <mike@...>
Subject: Re: Pop goes the PSU

In article <BAY101-DAV10E29E7028B4DAC16CEC2BA1060@...>, Mike
<profpep@...> writes

>    The caps to really worry about are the ones after the bridge 
>    rectifier. According to a drawing I have here, that would be C5, 
>    C6, C7, and C8.

H'm. I'd be more concerned about replacing C16 to C21 on the secondary
side.  I suppose, really, in view of the age of these PSUs, _all_ the
electrolytics should be replaced.

In any case, C9 is the one that's essential to replace.  This is a
200uF, 35V cap close to the switching transistor heatsink, the heat from
which causes C9 to dry out and fail more quickly than the others.

Failure of C9 causes the Beeb to appear dead when switched on.  If left
switched on for some time (a few to many minutes) it will eventually
power up.

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