Apple iigs power supply question #2.

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Joined: May 27 2013
Posts: 794

Hi, guys.

I am replacing the capacitors on an Apple iigs power supply. The model number is 699-0126.

I found something peculiar.

I am fiddling around with two of these power supplies.

All of the radial electrolytic capacitors on these have the same value except 1!

One has a capacitor with a value of 300μF 200V.

And on the other power supply has in the same location a capacitor with a value of 330μF 200V!

I could only find one place online that has a capacitor that has the value that can be used as a replacement (300μF 220V). This capacitor is very hard to find.

But I can easily get a capacitor with a value of 330μF 200v. I even think I can find one locally.

I would rather not have to deal with some place online that I have never heard of before.

Would it be okay if I were to replace the 300μF 200V capacitor with a 330μF 200V capacitor?

This capacitor is the largest one inside the power supply. I think it's capacitor C4 bit I am not sure.

What do you guys think?

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amauget's picture
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Joined: Jan 3 2011
Posts: 244
Re: Apple iigs power supply question #2.

Hello insanitor,

You don't mention the brand of the PSU : Dynacomp or Astec ?
Based on the schema and several pictures, I think it's an Astec one. You are probably talking about C4.
The problem is the value is 100µF/400V everywhere where I look.
A picture would help.

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speedyG's picture
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Joined: Nov 16 2011
Posts: 2413
Re: Apple iigs power supply question #2.

Hello,
both may just view still different supplies ?
one viewing US version ( with 100µF ) at netfrequency of 60 Hz
and the other
viewing the european version ( with 300µF ) at netfrequency of 50 Hz.....

short explentation:
C4 is used to "equalize" the voltage after it has been rectified.
Higher frequency at net means more duty cycles with shorter time of charge and discharge - demands smaller capacity
lower frequency mean less duty cycles and extended time of charging and discharge - that demand larger capacity

back to the question
the 300µF is the minimum value and 330µF is a permitted replacement.
speedyG

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Offline
Joined: May 27 2013
Posts: 794
Re: Apple iigs power supply question #2.

amauget wrote:

Hello insanitor,

You don't mention the brand of the PSU : Dynacomp or Astec ?
Based on the schema and several pictures, I think it's an Astec one. You are probably talking about C4.
The problem is the value is 100µF/400V everywhere where I look.
A picture would help.

You are right. It's Astec Model AA13581.

The pictures you provided match perfectly.

I called the store where I got all the other capacitors and I can buy the 330 Microfarad capacitors locally.

I will do this today so I will report back here. I will check the voltages with a DMM under load (from a running iigs).