I need to order higher tolerance ones. However, I was wondering, would a sensible strategy be to go through the ones that I have and find one that outputs a voltage closer to the spec? Or would that just be storing up trouble for the future?
Regards Rob > -----Original Message----- > From: Rob Jarratt <robert.jarr...@ntlworld.com> > Sent: Sunday, April 30, 2023 9:35 PM > To: 'Wayne S' <wayne.su...@hotmail.com> > Cc: r...@jarratt.me.uk; 'General Discussion: On-Topic and Off-Topic Posts' > <cctalk@classiccmp.org> > Subject: RE: [cctalk] Re: Rainbow H7842 PSU Fault > > 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 > > >> > > >> > > >>
