Transformer part ID please

Adrian Graham witchy at
Sun Jan 22 06:04:28 CST 2017

On 22/01/2017 07:31, "Tony Duell" <ard.p850ug1 at> 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.

Binary Dinosaurs creator/curator - the UK's biggest private home computer

More information about the cctalk mailing list