Re: IIgs power supply

[gregw@venus.itns.co.za (Greg Wildman)]

On 19 May 2001 11:42:36 -0700, Rich J. wrote:

> I started with 4 IIgs computers about 6 years ago,
> all working.  1 motherboard went bad, 1 battery
> went dead.  Down to 2 motherboards.
>
> The power supplies have all gone bad.  I am not
> loading the IIgs's up with cards, just 3 to four
> cards.
>
> I want to fix the power supplies.
>
> One clicks and buzzes when you turn it on.  The
> computer won't turn on and shows no signs of
> getting power.  It is a high frequency sound,
> not electric arcing.

Replace cap C7 near the big black finned power transistor heatsink. The
original is 220uF 10V replace with a 220uF 16V or higher. Make sure the new cap
is rated at 105 degrees centigrade. It dries out due to thew high temperature
developed by the power transistor heatsink.

>
> The other one does the same noise as above
> when turned on.  The Apple IIgs turns on
> for about 1/2 second (power light comes on)
> If you turn off/back on, it will not do it
> again.  Wait five minutes and it will turn
> on for 1/2 second again.
>
> I'll take a guess at the problem:  A capacitor
> has gone bad.
>
> Can someone let me know where some test points
> are?
>
> Where's the rectifier?  Are there good schematics
> or block diagrams of this power supply?
>
> With a little information I can troubleshoot it
> myself.  I looked through the FAQs and found
> that caps are the most common problem.
>
> There are no obvious signs of heat damage or
> cracked/broken/damaged components.
>
> Power Supply Says Apple Inc. on the end and
> Dyna Comp on the bottom.
>
> Rich

-- 
Heisenberg may have slept here.