Looks like the one I used is an L7812CV, which has a looser tolerance. I am going to have to order some tighter tolerance parts.
> -----Original Message----- > From: Wayne S <wayne.su...@hotmail.com> > Sent: Sunday, April 30, 2023 7:42 PM > To: Wayne S <wayne.su...@hotmail.com> > Cc: r...@jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts > <cctalk@classiccmp.org>; Rob Jarratt <robert.jarr...@ntlworld.com> > Subject: Re: [cctalk] Re: Rainbow H7842 PSU Fault > > The CT version is 4%, the ACT is 2%. > > Sent from my iPhone > > > On Apr 30, 2023, at 11:37, Wayne S <wayne.su...@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@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 > >> > >> > >>
