Originally Posted by Dougmeister
Yes, I have a volt meter.
What do I look for?
We're still talking about an S3 power supply and not the Premiere, right?
The first rule is:
ALWAYS KNOW WHERE BOTH ENDS OF THE TIVO POWER CORD ARE AT ALL TIMES!
Set the meter for DC Volts, lowest scale that's not lower than 0-15.
I assume there's a negative black lead and a positive red one.
Hook the black to the chassis on the side away from the power supply, either via alligator clamp if it has one or jam the probe into one of the cutouts and friction fit it.
There are colored wires coming out of the power supply board, some of which run to the hard drive combo power/data plug and the rest go to a plug that mates with a socket on the motherboard.
You're going to backprobe the ones in that plug.
You choose a wire and stick the probe down into the hole in the plug the wire goes into until you contact the metal tip at the end of the wire.
You need to have the motherboard at least connected as a load while the power supply is plugged in, if not both the board and the drive.
Switch mode supplies don't like to run without a proper load.
The black wires are ground, are in parallel, and should read 0 volts relative to the chassis.
All of the wires are paralleled with the others of the same color, so you only need to read one of each color.
The yellow wires should read +12 V, the red +5 V, and the orange +3.3 V.
If it's a 648 supply (original S3), there's a white or gray wire to power the OLED display on the front and I think it's supposed to be +7.5, but if there's a problem, it shouldn't be there.
There should be a sticker wrapped around the biggest capacitor listing the different voltages and amperages, or it'll be silkscreened onto the board itself.
As long as you're within half a Volt on the +12 V, and similar tolerance percentage on the others, the supply should be okay.
But test with the drive connected and then with it not connected to make sure that the readings are similar to indicate that the supply regulates properly when you add load.
You can also test to see if inserting a cable card makes an appreciable difference, if it uses them.
And remember, if you touch parts of the supply itself while it's plugged in, you could get a nasty shock directly from the wall outlet voltage, because it's not separately sheilded like a PC supply is when you open up the case.