18 Apr
2023
18 Apr
'23
5:27 p.m.
On 4/18/23 09:40, Tony Duell via cctalk wrote:
On Tue, Apr 18, 2023 at 2:51 PM Tom Hunter via cctalk
<cctalk(a)classiccmp.org> wrote:
True, but Bob Boschert was a pioneer in the field working with what
components were available. So don't be too hard on him.
--Chuck
The blown out resistor likely has "blown out" for a reason.
The replacement will probably suffer the same faith unless you find the
root cause.
As soon as I saw 'Boschert' mental alarm bells triggered....
Boschert made a particularly unfriendly (to the repairer) type of
SMPSU which I call the '2 stage'. I can explain how it works if
necessary, but be warned that with one of those if a particular power
transistor fails (and it often does), it takes out a couple of other
power transistors, the current sense resistor, numerous small
transistors, the regulator chip, the fuse and sometime PCB tracks.