Thursday, January 13, 2011

Repairing a Newton Power NPS-160DP or NPS-160DB B in a Gateway Computer from 2002

I wanted to install Skype for my parents-in-law on their old Gateway computer. This involved installing more memory, which should have been simple, but when I closed the case after putting the new memory in, the computer would no longer start (*completely* dead; no power at all).

A borrowed multimeter led me to the power supply, a Newton Power NPS-160DP. I initially thought it was dead, but when I took it apart (for fun) it sprang back to life again. Here are instructions for repairing it:

These instructions are for the Newton Power NPS-160DP or NPS-160DB B in a 2002 Gateway Microtower (I don't have the computer's model number anymore). In theory, these instructions should work with many other power supplies, however.

If you're not comfortable working with live 110v current do not do this. There is a high risk of electric shock in this process if you don't take precautions. I take no responsibility for accidents.

At every step you do here, you should plug the unit in and test it, plugging it out again immediately. If you get a response, stop the disassembly and test the unit on the motherboard (step 7 below). If everything works, close the whole thing back up again, testing the unit at every step, until the computer is back together.

1. Completely disassemble the power supply, carefully saving all the screws. You may have to cut one or two of the plastic ties on the cable-bundle to get the whole thing dissassembled. If, so, retie them immediately using anything to hand. Once that bundle gets loose, it'll be very difficult to get the power unit back together again. And it *must* be put back together exactly as found if it's to fit into the computer again.
2. Remove the circuit board from the chassis. This will involve unscrewing the a/c power socket and unplugging the fan. Do not lose the retaining screws for the power socket! If you do, you're sunk. They're best removed using a needle-nose pliers on the nut.
3. Note that there's a fuse on the circuit board, next to the mains socket. It's partially soldered into place. Test that first, obviously. If it's burnt out, you'll have to replace it. That should be easy, but I didn't have to do it, so I have no advice about it.
4. Plug the PCB back in (yes - to the mains). You should hear a high pitched whine (which I guess comes from the step-down transformers on the board). Try to avoid touching anything, as there's a lot of exposed electricity on the board at the moment.
5. Using an insulated screwdriver or any old stick, push the test button on the side of the PCB. The whine will change pitch and the green LED next to it will flash about twice a second.
6. If this happens, you have your power back. Note that once you plug the fan back in again, the test light will not flash when the button is pushed, but you will see the fan "bump" for a split second.
7. If you really need to be sure that you have your power back, you can lay it on an insulated surface just above the exposed motherboard of the computer and plug everything back in again (power to the board, the hard drive, and the CDRom drive; I think there were four separate plugs). Push the computer's power button, and if you get a boot sequence, everything is fine (don't boot the computer, obviously. Press the power button again to abort the boot sequence).

I found that I had to go through this whole process three or four times. I conjecture that there's some sort of very sensitive grounding-detector in the unit, which completely shuts the power unit off if the case is opened while power is present. Complete disassembly seems to be the only solution when this happens, but then you have to be exceedingly careful as you put everything back into the computer, or you'll trip the failsafe again.