Re: Power supply circuit help

Changed the transistor and it works like a dream.

What a great feeling!

Re: Power supply circuit help



Yep, it is indeed. E to B. I will change it.



I thought it must be something like that but I couldn't figure out how the variable resistor was affecting the base voltage. But now I see my schematic was wrong and that caused the confusion.

Thank you so much for your help!...

Re: Power supply circuit help

Thanks very much for your help R_J.

Yes, I can see that R1 is attached to ground as per your schematic. My mistake.

I will replace the transistor and also double check the orientation vs. the original.

Does anyone know what role the transistor plays in this circuit?

Hi

I have been trying to repair a simple power supply from a student microscope base (3 of them in fact). It has a 230 to 12V transformer which gives a 12V AC input to the attached schematic (which I think is correct but I made it myself, so there may be errors - please correct me where needed).

My knowledge of electronics is very limited and I'm struggling to understand what role the transistor plays in the attached circuit (and if it is shown with the correct orientation).

I've attached photos of the board (the image of the rear side is flipped to...

Re: New Members - please post your introductions here

Hi

I service microscopes and often have electrical problems to resolve. I am here to learn some theory and practical tips.

Thanks - it looks like a great forum.

John
Newcastle upon Tyne