Apple II A2M001 Power Supply

Intro

I have 2 Apple II power supplies which need some restoring. One had several parts picked from it, and the second was sold as-is. Although the two power supplies have different-sized PCBs with different layouts, the components on the two are exactly the same.

The shorter board is from December 1978. It’s labeled as A2M001 on the outside and 820-0003-01 on the bottom of the PCB. The longer board is from February 1979 and has no model on the outside. On the inside, it’s labeled as 820-0017-00 605-X001-00 on the bottom of the PCB.

Parts

Since the older 1978 power supply had several parts missing, I had to order replacements. These included the power transistor with heatsink, grommet, and power switch, all of which were a bit tricky to find.

I managed to find the Motorola 2N6543 transistor on eBay. I also needed the heatsink that held it in place. Luckily, Mouser had me covered, as they carried a matching replacement heatsink, the Aavid 501403B00000G (datasheet). Note that an insulator needs to be placed between the heatsink and the transistor; I used a cut piece of plastic.

For the strain relief grommet, I ordered a couple of replacements from Mouser. The Heyco 1114 SR 4K-1 (datasheet) was by far the best-fitting one.

For the power switch, I went with the TE Connectivity 1-1571987-5 (datasheet). It fit perfectly.

I also ordered replacement capacitors. Here is the list:

 

Repairs

Both power supplies needed some additional repairs. Below is a drawing of the PCB board.

The short-lengthed power supply had a very fast clicking sound when plugged in with a load. After several hours of troubleshooting, it turned out to be a bad transistor at Q1 the 2N3904. I also noticed that the previous person put in 220uf instead of 100uf for the capacitors, so I returned the correct capacitor. The date on them was from 2012, seems like someone tried to repair this around 10 years ago, but didn’t notice the bad Q1 transistor and ended up taking all these other parts out.

The longer power supply had never been opened before. When I did open it, I noticed that one of the original factory capacitors was inserted backward!  From looking at the inside, I don’t think this power supply was ever used. I guess the backward capacitor caused a problem after a couple hours of use and the power supply was pull out.

Here is a full list of components that correspond to the above drawing.