[cctalk] Re: Rainbow H7842 PSU Fault

That’s a good idea, I will try that From: Mattis Lind <mattislind(a)gmail.com> Sent: Tuesday, May 2, 2023 7:55 AM To: rob(a)jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts <cctalk(a)classiccmp.org> Cc: Rob Jarratt <robert.jarratt(a)ntlworld.com> Subject: Re: [cctalk] Re: Rainbow H7842 PSU Fault Not quite sure what you mean here. I had advice from a friend to bench test the control module by providing 14V to the input of the 7812. On the good PSU I can see the PWM operate, on the bad one the PWM is shutdown. And what happens if you feed in exactly 12 V on the output of the 7812? Would the PWM work then? By using a lab supply you could check if the circuit is sensitive to variation in the 12V supply. /Mattis Regards Rob