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My power supply wont work, whats wrong? Answered

I have an old AWA power supply that puts out DC between 10 and 24 volts.
i was running a motor at 24v and suddenly now stays at 24v. i turn the potentiometer and nothing changes
the voltage.

Whats wrong and how can i fix it?



7 years ago

You've blown the regulator electronics - motors are nasty loads - did you put a diode across it before you used your PSU on it ? ??

If this is a linear power supply and you're lucky, it may use a modern adjustable regulator, like an LM317, which is easy to fix, otherwise you need the circuit diagrams from somewhere - and then it will be the "pass transistor" which is probably a big fat power transistor fastened to a big-ish heat sink.

If its switcher based, its an order of magnitude more difficult to fix, but again, you might start by changing out the biggest power transistors you can see, but be careful, switchers will have some very highly charged capacitors - ones that might easily blow you across the room.


The MadScientist

7 years ago

I had exactly the same problem a few weeks ago when I was running a motor on one of my power supplies. I found that the regulator (LM7812) was stuffed so I replaced it and it worked, however there may be a problem with the pot so if you have an exotic regulator that costs a lot replace the pot first and see if it works.