On 22/01/2017 07:31, "Tony Duell" <ard.p850...@gmail.com> wrote:
>>> It looks to be part of a switching regulator circuit. Possibly to generate >>> other voltages from the 5V line. Can you post a picture of more of the PCB >>> around it. >> >> Its second output goes via an IN4148 to the -24V regulator: > > What do you mean by 'second output'? How many pins are used on this > 'transformer'? If only 2 it is just a simple inductor, again possibly part of > a swtiching regulator. There's 5 pins (5th for keying I guess) with 2 separate windings and I've just realised the 2nd winding (destination -24V) isn't fed from anywhere. It's only a 2 sided board and there are no top traces under the part. There's also some incomplete traces in that circuit so I wonder if there were planned enhancements for a Mark II that never happened. I'm marking up the back of the board for my own understanding as I type. >> The -24V regulator can be seen just above the 4 blue caps, The regulator >> that can be seen under the black wire is a 7812. The LF351N has -12V present >> at its bias outputs, the opamp to its right has no markings helpfully. > > What about that IRF523? That is a power MOSFET transistor and might well > be the chopper in the switching regulator circuit. It tests OK in my MOSFET tester. > Why do you assume the other 8 pin IC is an op-amp? Initially because of the way it's wired but I'm checking it now. Once I've marked up where the traces go the picture should be clearer. -- Adrian/Witchy Binary Dinosaurs creator/curator Www.binarydinosaurs.co.uk - the UK's biggest private home computer collection?