31 Aug
2014
31 Aug
'14
3:42 p.m.
On 29/08/2014 20:44, Tony Duell wrote:
Are we talking abotu the same supply -- the SMPSU from
a VT100 (and not
the VT101 supply which is very different)?
I find the VT100 PSU to be quite pleasnat to work on. In common with many
other DEC supplies of that period, the chopper cotnrol circuitry
(oscillaotr, etc) is on the output side of the isolation barrier and runs
off its own little linear PSU. So yo can remove the chopper transistor,
power up, and clip the 'scope wherever you like around the chopper
control IC.
-tony
Yes, it's the VT100 PSU with the small linear supply for the start-up. I
don't know for sure there is anything wrong with mine as it seems to
work OK. Maybe I'm trying to debug something which isn't actually a
fault? When you've worked on these in the past have you noticed any
components getting hot (particularly R27)?
Thanks,
Matt