7 Oct
2011
7 Oct
'11
12:10 p.m.
On Thu, 6 Oct 2011, Tony Duell wrote:
No, it's not an SMPSU... A dead short in one of the smoothing caapcitors
in the TRS-80 may well kill the associated rectifier (either the 4-diode
bridge on the CPU board or the 2 diods in te brick), but the fuse will
almost certainly blow before the transformer fails.
Just don't short out the fuse to get it going again. Next time you have a
fault, the transformer may burn out.
[Incidentally, I had an SMPUS where there were 3 power transistors, half
a doxen small-signal transistors, a controller IC, a couple of power
resistors and a PCB track all protecting the mains fuse. Or at least all
those failed, some transistors blown apart, track melted, etc, before the
fuse failed]
-tony
Secondly, let's think about that power brick.
The transfomer rarely
fails, normally the (soldered in) fuse goes first if there's a short on
the secodnary side (note that a shorted smoothing capacitor or rectifier
on the CPU board will blow this fuse). So the only things you're likely
to have to replace i nthe brick are the fuse and the diodes. Are those
really that hard to find? My junk box is full of 'em...
There are no expensive, hard to find parts in there to protect that fuse!