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Help me troubleshoot this IIGS

sev

Experienced Member
Joined
Mar 30, 2014
Messages
132
Location
Los Angeles
Hey everyone, just picked up a IIGS, it is cosmetically in pretty good condition and came with an echo card and a hard drive. I cleaned it up, and went to turn it on and nothing happens. The power LED flashes for a second, then nothing happens. When I turn it off, a second or two later I hear a quick shriek from the power supply and that's it.


The power supply is a Dyna somethign or other 699-0126.

I took it apart and visually i dont see any caps that are bad, none are bludged or exploded...

Any ideas how I can fix??
 
When I turn it off, a second or two later I hear a quick shriek from the power supply and that's it.
The power-down shriek is pretty typical as the switching slows down into the audible range. Have you tried pulling every card and plug out of it (except the power) to see if that makes a difference?
 
The power-down shriek is pretty typical as the switching slows down into the audible range. Have you tried pulling every card and plug out of it (except the power) to see if that makes a difference?

yeah i have nothing on the system except the IIGS mobo. No disk drives no cards.

The 12v line gets about 2.20v and the 5v line gets almost nothing. Im pretty sure its the power supply


I dont see any bad caps. Any way to fix this?? Or do I need to replace completely?
 
You won't necessarily see bad capacitors. In fact, almost never are there visual symptoms.

You could blindly replace them and hope it works (and it might) or pull components and test them. Or, just replace the power supply.
 
You won't necessarily see bad capacitors. In fact, almost never are there visual symptoms.

You could blindly replace them and hope it works (and it might) or pull components and test them. Or, just replace the power supply.

I see a rebuilt kit for this particular supply on ebay. I do know how to solder but Im scared of being zapped haha.

i havent found any replacement power supplies for sale yet.
 
Build a chicken stick and discharge everything inside the power supply before working on it.
 
Sorry for the jargon :mad:

It's a nonconductive stick that has a conductor on the end for discharging capacitors. I like to use a voltmeter, but a lot of people prefer a chicken stick, and actually it's technically safer than using a voltmeter because there's always a chance the voltmeter is lying.

Here's a fancy expensive one http://phenixtech.com/Files/Admin/PDF/40400_Discharge_Ground_Sticks.pdf

But, you can build a simple one with a wooden dowel or a piece of PVC pipe and an alligator clip.

There's another one here http://www.w6kan.com/sb200.htm but I don't like that one because running the wire through the handle is problematic.

For your purposes, a 1' length of 3/8 wood dowel and one of these brass hooks or eyelets screwed into the end, with a wire attached between there and chassis ground would suffice. All the parts can be sourced from a local hardware store for less than $5.
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Yeah, the often fanless environment of the IIgs like the other Apples of the time meant that the caps dried out internally and showed no external form of failure. Both my II+ and IIe did that and so did my 512k and Plus.
Recapping the PSU (secondary, primary and the AC line filters) normally brings it back.
 
The power LED flashes for a second, then nothing happens. When I turn it off, a second or two later I hear a quick shriek from the power supply and that's it.
Gotta ask, what do you have hooked up for a monitor? My fully working IIgs exhibits these exact same symptoms when I tried hooking up a Mac>VGA monitor adapter, I assume the adapter is shorting one of the rails causing the PSU to freak out. Unplug adapter, power back on, all is happy.

May not be your issue, but I thought I would toss that out there ;-)
 
I have the regular IIGS monitor installed.

So the problem was indeed the power supply, I replaced it with another unit and everything works perfectly
 
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