Symptoms:
The power supply is chirping and it doesn't give the output voltage which it is supposed to.
The output voltage is this:
pin 3: fluctuates bewtween +1 and +2,7 - should be +5
pin 4: fluctuates bewtween +1,3 and +1,9 - should be +12
pin 5: fluctuates bewtween -0,4 and -2,3 -s hould be -12
pin 6: fluctuates bewtween -4 and -8 - should be -5
I'm not an electronic Expert and I only have a simple multimeter to measure it, so it's difficult to be precise.

It's measured with power supply pulled out of the machine, so it is without any load.
(I do have another power supply that works and the output is steady with the correct voltages without any load.)

The broken power supply failed after my apple II had been sitting in a box unused for about 25 years, and it worked fine for about a week with a few hours work time each day, before it developed the fault.
When I look at the capacitors and the other components of the power supply there isn't any "smoking gun", they all look fine (to my eye).
I have changed all the electrolytic capacitors and put in new ones, including the C7, and I have also changed the 0,1 uf MP capacitor.
That changed nothing.

The power supply is the ASTEC model AA11040C 230V.

Which component should I change now?
Any advice?

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inspection results to one severe fault,
1 recommended correction
and 1 inspectionpoint.

The severe fault is the missing R25 resistopr marked with purple light shading at the PCB
and in the circuitplan and layoutplan. There are still broken wires there so
i must assume that it has broken away or been cut with tweezer......
The value is 100 kiloOhm and it may be a regular 1/2 Watt resistor with 10% tolerance or less.

A well known common issue is the problem with the C7 electrolytic capacitor.
Apple populated that capacitor with 10 Volt limit - but it is strong recommended to use a
electrolytic capacitor with limit of at least 16 Volt better even 25 Volt but not higher.
It often leads to false feedback issues ( indicated by that chirping sound ).

The third point is a question:
Up to my feeling that wire inside of the fuse looks very thin and not that strong to be
used for 2,5 Ampere...... I�d guess it only to be capable of about 1 Ampere...
Please inspect the imprint of that fuse at one of the metal toppings ....
it should read 250 Volt / 2,5 A.
If not it�s recommended to replace with correct value.

And please remember testing is only valid with load at +5 Volt and + 12 Volt !
A old harddisk would serve excellent as load.

If you don�t know about pinout of the harddisk google it by pictures....
there are plenty pictures out there displaying the powerconnector pinout of harddisks....

below are the pictures from the PCB to locate the mentioned parts.

this is the layoutplan of the powersupply.
Allthough it�s from the B-Version there have not been many changes in the layout ....
only some parts have changed and the related values of some parts...

I hope this should solve your problems....
just give here feedback of the result....







http://www.applefritter.com/content/appl...-voltage-output