25 Nov
2010
25 Nov
'10
9:57 p.m.
I finally found time to take a look at the PSU. This
machine has two PSUs
and there seems to be some mains distribution happening before the power
gets to the PSU. The input to the PSU is a 6-pin connector and right next to
that are four capacitors marked 250WV and 680uf. Are these going to be the
Almost certainly yes.
The incoming mains is rectified and smoothed. Look at the connections ot
these capacitors, you may find that pairsof them are connected in
parallel.
Quite often you wil lfind 2 capacitors in srries, +ve of one to -ve of
the otehr. The 'free' +ve end is the main B+ rail, the 'free' -ve end is
the 'common' rail of the maisn side of the PSU (which for obvious reasons
must not be connected to ground). The centre tap (the conection between
the capacitors) is often connected to the input voltage selector swithc
or cirucit, which will convert the input rectifier circuit between a
simple bridge rectifier for 230V mains and a voltage douber fro 115V
mains. In both cases you get aound 350V across the pair of capacitors.
first "pair" of capacitors you mention?
There are another two identical ones
somewhat further away.
None of the capacitors, or any of the other components, appear to be visibly
damaged.
OK. Alas that's ofthen the case. It's always worth carrying out a visual
inspection, but most of the time it reveals nothing.
There is no fuse I can see, but there is a circuit breaker.
Which I assume has not tripped?
-tony