IIx Power Supply on the Fritz?

#1 Fri, 10 Jun 2011 - 21:23

I have a IIx that I have been restoring to working order, and it's mostly working well. I've got it currently configured, as follows:

8mb RAM

9gb UW SCSI Seagate Barracuda

Radius PrecisionColor Pro 24X

FWB JackHammer

Radius Rocket 33 w/8mb

ProAudio Spectrum Mac

I'm pretty happy to have all of this, but my power supply is starting to show signs of it's age, I think. The IIx now only stays on while the power key, on the keyboard, is held down. I've heard it mentioned that this may indicate a bad power supply, but I'm not sure. Both of my PRAM batteries show 3.6v, so I don't think it's them.

Any thoughts?

Thanks!

- Alex

#2 Sun, 12 Jun 2011 - 03:43

grab a multimeter and watch the rail voltages. do they sag beyond tolerance? if so then i would say the power supply may be at fault.

#3 Mon, 13 Jun 2011 - 08:13

I tried two different power supplies but with not luck.

Eventually had to swap out the capacitors to get it to stay on !

#4 Mon, 13 Jun 2011 - 09:43

Hi patatas,

what capacitors did you replace - was that in the power supply or on the motherboard? Have a similar issue with my IIfx - only powers on with the power key held down.

Thanks

JB

#5 Tue, 14 Jun 2011 - 00:12

I seem to recall that the two soldered-on PRAM batteries on the 6-slot II-series Macs will cause this behavior when they're flat.

Am I right that they are what you replaced patatas?

#6 Sat, 8 Oct 2011 - 23:58

I had a similar issue with my MacII about ten years ago. Soldered in two new batteries, but that did not help.

I located the problem in so far, as the trickle voltage from the batteries did not reach the psu.

Starting the psu with a seperate battery did work, but I gave up there. :-(