Model 2 Issues

[the wizard]

A while back I brought out my Model 2 to plug it in and fire it up. all went great until a few minutes later the power light and screen went dark but I here things stirring inside. So now I ask the Model 2 guru's for advice as to were the issue would be AKA Solder joint etc. Thank You.

 

[the wizard]

Replaced 1 (the biggest) RIFA Cap on my Model 2 and no joy. Still no Screen or Power light on. Have to wait until that little China Man in his canoe brings me the smaller cap. Don't see any blown fuses. I will keep checking, kinda hard with out a VOLM meter. any suggestions will help greatly.

 

[NF6X]

The Rifa caps are just filters to help prevent the computer from radiating too much noise from its power cord. They aren't critical to operation. Though they should be replaced with correct caps of the same value and with the same or better safety classification, they can be removed while you're waiting for the replacements to arrive. The ways they might cause functional problems are by either damaging adjacent components when they burn up, or by shorting out the AC mains and thus blowing fuses.

While I can't be sure without examining the power supply in person, I'd say that just the Rifa caps probably are not the primary thing keeping your computer from waking up. You'll need to dig deeper. Very carefully, of course... there are lethal voltages present in that power supply!

Section IX of the Model II Technical Reference Manual describes the power supply:

https://github.com/pski/model2archive/blob/master/Hardware/Model_II_Technical_Reference_Manual.pdf

It includes some limited troubleshooting instructions, though we usually end up on our own when we get to the "return power supply to the depot" stage. It's important that you don't run the power supply without a load. The above manual describes the minimum load necessary for bench-testing the power supply.

I'm presently trying to fix my Model 6000's power supply, which is a different (but similar) model. It's still outsmarting me. Here's a picture of my test setup. The dummy load I built is over on the right side.

 

[pski]

If you get a multimeter (not a lot you can do without one other than looking for obvious physical issues), start by testing voltages coming to one of the empty card cage slots. Pins 5/6 should be 12V and 9/10 should be 5V. If not, you have either a short somewhere or a PS issue.

 

[NF6X]

One thing that I overlooked: There are two different power supplies described in the Model II Technical Reference, in sections IX and XV. Make sure you're looking at the right section. Good luck!