What is the writing on the side of the transformer? If it has a 24 Vac primary, it probably is a custom part. Also, it looks small for 30 W plus regulator overhead.

The power supply section is a bit more complex than two 78xx regulators. I see two different sized bridges, an opamp, and multiple small transistors.

ak

 

Funny but that isolation transformer is 24 volt on the top left you supply it with 24 volt AC. From there it supply's the chips on the board and
it has 5 volt power and 12 volt power the isolation transformer was only to power the uC and the chips it uses the 12 was used for off board stuff.

I had a box of them boards at one time.

Oh I forgot what was funny I had about 20 ton's of parts boards and the like I removed one of them transformers I was mess around thought I had something else hooked that baby to 120 volts cooked it before I could unplug it.

It's a shame what happen there best job I had I did a lot of control work there