Apple II Plus - Trash to Treasure - Part 1

One of my goals in Retro Computing is to learn about older and older computers, and work my way back in time, one generation of computers at a time.  The nostalgia factor is certainly important for me, but I’m also interested in the tech that came before.  In my own retro computing development, I’d been keeping my eye out for an Apple II Plus machine.  I have an Apple IIe that I’ve already mentioned, and have been interested in the experience of using the original Apple II's since I’ve never owned one of the original “Trinity” of home computers.  Finding an original Apple II (not a Plus) seems a bit out of my price range at this point, but perhaps someday I’ll be able to repair an original Apple II.

My opportunity for a II+ came in mid November of this year, when a trusted retro computer seller on Craigslist posted a Bell and Howell “Darth Vader” computer in need of some serious help.  As Apple fans will know, this was a partly re-branded Apple II Plus, Bell and Howell painted it black, and since it’s a bit more rare it’s more valuable.  The seller and I had a phone conversation about the state of the machine, which was poor, but I was able to convince him to sell me the machine regardless of the state.

The state of the computer was not good.  The biggest problem with this computer was that the top cover had been removed before the computer was stored.  This meant that dust and dirt got inside.  I even found a couple of acorn tops as I was cleaning inside.  The main board had a significant amount of dirt on it, and there was one chip (one of the ROMs) that had bent pins  It seems likely that something very heavy was dropped onto this chip causing the pin legs to bend.

So on intake, it was obvious that I should not even try to power the machine on without doing a lot of cleaning first.  I started by taking the top half off the case, removing the power supply, main logic board, keyboard, and backpack from the unit.

I started with the logic board.  I used the cleaning method that Adrian Black has been demonstrating, warm soapy water in my basement laundry sink.  I used Dawn dish detergent, warm water, and brushes for the initial cleaning.  It took quite a bit of time because there are more than 80 chips on the board that all needed to be cleaned around, but it was very gratifying to see how much better the board looked after.

Also, at this point I was able to get a look at the date code on the board and discover that this II Plus was made in 1981, so this would have been the third year of production for the II+, starting in 1979.  After the initial clean of the logic board, I shifted gears to the power supply.   I had already serviced the power supply in my Apple IIe, but this one had an additional rivet on either side that I had to drill out.  The RIFA cap was certainly on its way out (bulging) so I'm glad I saved the smelly mess associated with a power on test.  I removed and replaced with a new X type filter cap that I had in stock.  When I put the power supply back together and tested voltages, it was not working correctly.  I remembered that as I was re-assembling it, the circuit board had flexed quite a bit.  Since this board has a heavy transformer in the middle, I think this design is prone to getting cracked solder joints at the transformer.  After I reflowed the joints on the transformer and several other components while I was at it, the power supply was working with all voltages reading good.

Next, I tackled the keyboard.  One of the things I dislike about the Apple II Plus is the use of ribbon cables with DIP connectors on the end.  I didn’t realize how fragile these were, and as I was taking the computer apart, I broke pins on the interconnect cable between the logic board and the keyboard.  Thankfully, I was able to find this article online, I ordered the replacement cable from DigiKey, and it is on the way.  This keyboard has the SKCC Short Stems with the extenders installed, and it ended up being significantly less dirty than the previous one I’d cleaned. My son especially enjoys keyboard cleanup (I think it reminds him of Legos), so he helped me with this part of the project.  We pulled all the keys and gave them a soak, he helped me go over them all with a toothbrush, they look great.  I then worked on the keyboard deck, using the same procedure I described in the Apple IIe article with lots of Isopropyl and DeOxit.

The next day, after the main logic board had dried, and on further inspection, I needed to do more spot cleaning on the logic board.   This time I used Isopropyl and  Q-Tips to get in close to each chip.  I was also able to pull out the damaged ROM chip, inspect the socket, and re-bend the pins back into place.  I made a note of the location since this may require further inspection and repair, but at first glance, it looked like that socket had not been damaged, and none of the pins broke off.

At this point, I was able to give the system its first power up, a very exciting moment indeed.  Sadly, there was no video from the machine.  So, this sent me back to looking more closely at the board.  What I noticed was that because there had been so much dirt on the board, there was dirt on the legs of many ICs where they entered into the sockets on the board.  So, as time consuming as this would be, I felt it would be important to pull every IC out of the socket, inspect the IC, clean the legs if needed, and spray De-Oxit into every socket.  Given that there are more than 80 ICs, I divided this task up into a couple of parts.

During this part of the repair, I broke multiple legs off three different ICs.  Again, using another trick I’ve seen from Adrian Black, I was able to solder a small (28ga) solid copper wire back on in place of these legs and get the chips plugged back into their sockets.  I’m super happy that I didn’t have to order any additional chips. (Yet, knock on wood)

On completion of reseating all of the chips on the board, it was time for another power on test.  This time, there was Video, along with the Apple ][  logo at the top and the ] BASIC prompt, a very happy moment indeed!

At this point in the repair there remains a good deal more work to do; the keyboard is non functional, the RAM should be tested, I should add a Floppy Disk controller, but this article has gotten a bit long so I will leave off here for now.