Apple II

[ashiekh]

https://en.wikipedia.org/wiki/Switch...e_power_supply

"
Apple II is designed with a switching mode power supply. "Rod holt was brought in as product engineer and there were several flaws in Apple II that were never publicized."
"

This seems to imply flaws in the power supply; if so, does any one know what they were?

[Tim@PSUTest]

I seem to recall the +5 volt rectifier failing shorted.

In any case, here is a link to an archived forum:

http://www.vcfed.org/forum/archive/i...p/t-13620.html

BEWARE: The non-Astec supply DOES NOT have bleeder resistors across the main filter caps. If they are charged it takes a LONG time to bleed off and represents a major shock hazard. It's DC voltage which will cause your muscles to clamp down, making it hard to release that board.

Yes, I had 2 scars on my hand that took about 9 years to fade out from one of those non-Astec ones.

If those aren't the fix, let me know. I've repaired a lot of those over the years when I used to work for a grey market Apple repair shop.

Generally they are easy repairs...

Astec unit: Replace 1 cap in the feedback section
Non-Astec unit: Replace 1 cap and 1 resistor in the feedback section

Beyond that, it's a matter of simply looking for shorted diodes - both the bridge rectifier or the low voltage side diodes. If the fuse is blown, it's the bridge rectifier.

Those tidbits will fix 95+% of the Apple II+/IIe power supplies.

[ehume]

As I recall, the Apple][+ (my 1st computer) was a line-oriented machine that only had 64k RAM because I put a memory card in SlotZot. It came with 48k.

The old dear ran with line input. This was 1.5 decades before the Internet, and progress was fast in those days. A museum piece. A running Apple II is not worth resurrecting, IMO.

[Jon Gerow]

A running Apple II is not worth resurrecting, IMO.

But a IIGS is!

I played Hard Hat Mack and Jumpman for HOURS on that platform.

[Tim@PSUTest]

It would be worth fixing an Apple I computer:

One of the first-ever Apple computers just sold for almost $500,000—take a look

https://www.cnbc.com/2019/05/28/wozn...christies.html

I do have an IMSAI 8080 computer I built from a kit in 1976 that worked last time I powered it up a couple of years age. It was worth around $2,500.00 or so last time I checked on eBay.

I am planning on retiring in a few months. Maybe I will see if it still works at that time.

[ashiekh]

Doesn't Christie's take half the sale price?