Apple III main capacitor replacement question...

Those caps look pretty typical. And the filter cap blowing is very, very typical. The replacement filter caps I use are 275v.

If by any chance you cannot find a cap with the voltage rating that you need, then there are several general guidelines to follow. I am assuming the information I am about to give will be of use to you since you have run into a problem which is easy to resolve.

1). The caps from the time these computers were made were larger than the ones used today. This means that using a replacement cap from today with the same physical size of the original will in general have a larger voltage rating.

2). The voltage rating is an indication of the voltage the cap can withstand without blowing itself out or leaking. In most cases you may replace the original cap with one of a higher voltage rating but don't go too high.

3). Never select a cap with a lower temperature rating than the one that you are replacing unless you are sure that the cap will never be exposed to such temperatures.

4). If you go to Digikey, you will find other characteristics for caps that you may select. For example, lead spacing, ESR, physical size, radial or axial, etc,.

5). If you are replacing a polarized cap then replace it with another polarized cap.

6). Never buy a cap that is known to have been manufactured with the stolen formula.

Read this website for details:

http://www.badcaps.net/index.php?s=62bb87cb71136174a33c0e09e9cbec50&pageid=causes

In the future, when you grow on to work on more complicated circuits, you will then have to take into consideration things like ESR. Each circuit when designed properly must take into account it's purpose, function and tolerances.

Now that you have started out, do some research on ESR. This will help you familiarize yourself with the wonderful world of electronics.

Read these articles:

https://en.wikipedia.org/wiki/Equivalent_series_resistance

http://forum.allaboutcircuits.com/threads/understanding-capacitor-esr-ratings.28175/

When starting off, you may want to avoid those articles which use too many scientific explanations. They typically explain how everything works, but don't do much in terms of cap replacement. When you move onto that level you will need that info for designing circuits.

I know it's a 22uf but does anyone else have the specifics so I can order it.

Samm,

I had one of these let go this past weekend on a IIgs. Note that it is 0.22uF, and not 22uF.

For reference, mine is marked PME 271 M, with a 20.3mm lead spacing, although a hole exists for a 22.5mm spacing as well.

These are "safety rated" and should be replaced with an X class capacitor.

Some alcohol cleaned up the residue from the smoke and greatly reduced the smell.

Mine didn't blow the fuse, and I removed it while I wait for a replacement. In my IIgs power supply, there are two of these, and a pair of smaller 4700pf Y class capacitors as well.

In your image, I also see an X-class 0.1uF capacitor.

My God... ChristopherB, you are RIGHT! These are safety caps all right.

Samm, read this thread to get familiar with them:

http://www.applefritter.com/content/apple-iigs-power-supply-question-3

Samm328, the higher the voltage capacitors are rated, the better if you can physically mount (fit) them in the given room of this PSU. Don't bother with ESR, this is related to capacitors running at higher frequencies (usually tens of kHz) used in switching stages of PSUs.

I mentioned ESR because of that thread where I learned about the safety capacitors. I posted a link to that thread but here is a quote from it:

...You might consider getting one of these http://r.ebay.com/SVSSLL for testing caps. It's low price and they work well for measuring ESR. It's not lab grade but will help you find bad caps that you won't find with a multimeter.