I finally managed to replace the power supply of my Apple IIe with a "Mean Well" PT-65B switchmode power supply. As you can see from the photo, it fits nicely into the metal box of the original power supply, and once the box is closed, no difference can be seen. Here is the photo with the metal box still open:
The yellow circle is the new power supply module mounted in the original shell. Monitor shows "Wings of Fury" loaded from floppy disk and running fine. (Red arrow points at potentially bad original Apple 80 Column / 64 k RAM card, more on this later).
My IIe now has a much better power supply which will work worldwide, with any line voltage and frequency, unlike the original power supply which was for 220V (it's an Europe / PAL version Apple IIe "Made in Ireland").
If you are reading this and are interested in such an upgrade / replacement, I could write more about how it was done. There are no electrical issues, anyone could do that, but there are mechanical issues which need to be solved (and frankly, my first solution for that failed).
WHY TO REPLACE THE ORIGINAL POWER SUPPLY PCB COMPLETELY
You might ask why I did not attempt to repair the original power supply (only the usual culprit, the "Rifa" capacitor had exploded / cracked open). The reason, other than the 220V issue which limits the Apple IIe to my lab, where I have a step-up transformer, is that all the electrolytic capacitors in the original power supply are 40 years old, and beyond their safe life span. Which means they all need to be replaced to have a reliable power supply which would not cause more trouble down the road. And unlike some people believe, it is neither trivial nor cheap to replace the electrolytics in a switchmode power supply. They need to be chosen carefully to be suitable for this application, and "normal" electrolytics designed for filter purposes after an AC rectifier just won't do. These are specified for 120 Hz operation only, while the typical switchmode power supply works at more than 100 x that frequency. For electrolytics in switchmode power supplies, ESR at high frequencies (up to 100 kHz or more) and ripple current ratings at higher frequencies are critical, otherwise, they might just overheat and explode. So be warned, don't attempt to replace electrolytic capacitors in switchmode power supplies unless you are competent in this field of engineering. Now, the bad news is that suitable electrolytics are special types which are so expensive that replacing all of them would cost more than a brand new PT-65B. Besides the mechanical issue that none of the modern replacements have the same footprint anymore. Even electrolytics did shrink in size in the past 40 years. This mechanical complication is worse than you might think - the issue is how to bend the leads properly without damaging the seal of the rubber plug. It can be done, but then the next issue is how to prevent them from wobbling around, they need to be glued together somehow. Same reason why "Mean Well" puts white silicon goop in their power supplies to secure larger components, like electrolytics, in place. All this conspires against replacing these old electrolytics in the old power supply PCB. IMHO, it's simply not worth the time, money, and effort.
NEW POWER SUPPLY WORKS FINE ! BUT A CARD DOES NOT WORK !?
I've tested the new power supply together with a disk drive, and all works well. Alas, I found out that Broderbund's "Wings of Fury" game, which needs 128k of RAM, did refuse to work with the original Apple 80COL/64K Memory Expansion card (red arrow in photo). It terminates the load with the message that it needs a 128k machine to run. I have a Taiwanese clone of this card which works, and the game loads and runs with it. So there is no reason to suspect the new power supply.
IS THERE A GOOD WAY TO TEST THE CARD ?
If you have a hint how I could test the original Apple card for memory faults, let me know. I think there ought to be a way to do this with the built-in diagnostics-in-ROM, but my internet searches did only yield useless clutter, as I am not set up to make real floppy disks from images, so I can't load any diagnostics which float around in the web into my machine, except if they would be AIFF or WAF files for cassette interface load.
Oh, and please don't forget to comment if you want to know more about the PT-65B conversion.
- Uncle Bernie