[cctalk] Re: Rainbow H7842 PSU Fault

-----Original Message----- From: Tony Duell <ard.p850ug1(a)gmail.com> Sent: 25 June 2023 17:52 To: rob(a)jarratt.me.uk Cc: General Discussion: On-Topic and Off-Topic Posts <cctalk(a)classiccmp.org>rg>; Brent Hilpert <bhilpert(a)shaw.ca> Subject: Re: [cctalk] Re: Rainbow H7842 PSU Fault On Sun, Jun 25, 2023 at 5:33 PM Rob Jarratt <robert.jarratt(a)ntlworld.com> wrote: short across two of its terminals, so I am ordering a replacement. I tested the PSU, without the mains bridge rectifier and without the diodes on the output of the startup transformer. I got 24VAC on the output of the , the lamp limiter bulbs did not light and the fan in the power switch unit turned. So it looks like the startup transformer is actually OK. It's possible that the rectifier just failed. Or it might have been damaged because it had to pass too much current due to a problem in the main chopper circuit. I would certainly check the chopper transistor for shorts now. -tony