30 Apr
2023
30 Apr
'23
6:37 p.m.
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