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Posted by: NARP74 Aug 30 2026, 04:43 PM

Can someone suggest a decent 12v power supply for bench testing automotive parts and stereo equipment? I have some projects coming up that this would help if I had one.
Not lab grade. What do I need?

Posted by: Ninja Aug 30 2026, 05:10 PM

Power supply for a desktop computer puts out an accurate -12.5V.

Small units push 300watts
Many are over 500watts.

I've used them for testing small 12V automotive stuff for years.

Used junk out of an old desktop should function fine.


Just using a 12v car battery will work fine as well.
All of them are far more than 500 watt capable...

Edit: Those power supplies ALSO produce a clean -5V source.

Most digital fuel injections use multiple 5V "drivers" from the ECUs for the sensing elements.
Those units (MAF/MAP/TPS/CTS/lots of others) always have at least 3 wires. 5V reference/ground/sensor signal

The old junk power supply can supply that 5V reference single just fine.

Posted by: Superhawk996 Aug 30 2026, 06:09 PM

Sort of a trick question.

Here’s what I use.

For stereo repair you’re going to need higher DC voltages to power the rails - usually 32V & 3A is enough for solid state circuits. You will also need a dual power supply - one rail will be positive voltage and the other rail will be negative voltage.

For 12v work the 3A limitation is too low to power things like fans, starter solenoids, etc. In those cases where I need high current, I’d just use an actual 12v battery. The 3A limitation is a non issue for other things like lights, gauges, coils, radios, etc.

I originally started decades ago with the 12v 3A Radio Shack power supply on the left but honestly the Tenma variable power supply is 100x more useful and they can be had at reasonable pricing. Google.

A low amperage regulated power supply is just the ticket for hooking up to a freshly restored car. Much better to find any shorts with a limited power supply than hooking up an unregulated battery that can supply hundreds of amps and waiting for the smoke. Word to the wise.



Note: if you’re going to be doing stereo work you need to build a dim bulb tester at a minimum. Not going to go into the details of what it is or how it works here. Google or PM me. But seriously you need this at a minimum if you’re trying to fix home stereo gear.

Posted by: NARP74 Aug 31 2026, 11:41 AM

This will just be for set up and testing. Unless I let the smoke out.

Posted by: DennisV Aug 31 2026, 12:07 PM

I https://www.amazon.com/dp/B01AZLA9XQ and used it to bench test my vintage radios. Assumes you're coming from 120V AC. Not sure if 2A is enough for your needs...

Posted by: Superhawk996 Aug 31 2026, 12:12 PM

I misunderstood what you meant by stereo.

In that case go with something like DennisV has posted.

Posted by: NARP74 Aug 31 2026, 12:15 PM

For automotive systems.

Posted by: DennisV Aug 31 2026, 02:08 PM

If you're just doing car radios, here's a couple more links that might help:
https://www.dennisvogel.com/cars/radio-check-sibilance-sibilance/
https://www.youtube.com/watch?v=Hd9-4Q6CM54

Posted by: billh1963 Aug 31 2026, 03:58 PM

Yeah......you probably don't need my setup

Posted by: NARP74 Aug 31 2026, 04:17 PM

Nice setup!
I used to get to play with some of that stuff, long time ago.

Posted by: Superhawk996 Aug 31 2026, 07:19 PM

Nice reel to reel

Posted by: NARP74 Aug 31 2026, 07:31 PM

I have some reel tapes in the basement, nothing to play them on.