[cctalk] Re: Rainbow H7842 PSU Fault

On Apr 30, 2023, at 11:37, Wayne S <wayne.sudol(a)hotmail.com> wrote: Spec sheet for the 7812 shows 2 versions - 4% and 2% tolerances. So the voltages your measuring are within the 4% part. Maybe you do need the 2% one. Sent from my iPhone > On Apr 30, 2023, at 11:26, Rob Jarratt via cctalk <cctalk(a)classiccmp.org> wrote: > > I think I have found a possible cause, but not too sure what to do about it > if I have. > > I had to replace the 7812 regulator that supplies Vstart. The new one has an > output that seems to vary between 12.2 and 12.4V. The 7812 on the good PSU > outputs a steady 12.1V. I think that is enough to cause the E3d comparator > to turn the comparator off and allow its output to float high. > > I suspect I may have used one with a wide tolerance rather than a narrow > one, or just have a bad one. It should be a genuine part as it came from CPC > Farnell. Not quite sure why the output varies on the bad one though. > > Regards > > Rob > > >