Apple IIc re-capping. Part 1

Having got some time in my hands, I decided to complete the re-capping of my Apple IIc (see Part 0 here), check if the machine works, upgrade the MON rom and finally run a self-test.

The Apple IIc naked on the table, ready to be tested

First of all, I had to open the floppy drive, swap the caps on the bottom and top circuit boards, grease the mechanism and clean up the magnetic head.

Floppy drive exposed!

While I was at it, I desoldered the 74LS161 that the motherboard uses to generate the clock signal for the serial port controllers. The very early motherboard revisions (and mine is apparently one of those) suffered from a timing problem on the serial ports, rendering them mostly useless at speeds exceeding 300 bauds. A simple fix (which is what Apple actually did on newer boards) is replacing the '161 with an oscillator running at the correct frequency of 1.8432Mhz. I don't have one, but I prepared the board just in case. A working serial port is very useful if you need to run ADTpro! [UPDATE: Apparently, ADTpro is perfectly usable with my '161-equipped board and an USB serial adapter]

After all this, I turned up the machine and after a rattling sound I got greeted by this:

Minimalism at its best.

While this is a very good sign, it's still not a confirmation of the complete well-being of the computer. The first version of the MON (mine was 342-0272-A) rom for the IIc doesn't provide a self-test facility. This can be solved by swapping the mask ROM with a properly programmed EPROM (I used a 27C256 programmed with 341-0445-A), cutting a jumper trace marked W1 and soldering another marked W2.

MON rom replaced (just above the speaker)

Now the computer can test itself by using the proper key combination (CTRL-Open Apple-Closed Apple + Reset)! Well, at least some basic functionality and the RAM gets checked. Better than nothing, right? You also get the added bonus of 3.5" UNIDISK drive support. Good luck finding one.

SYSTEM OK
Now go about your own business.

Ok, now that the system passes the self-test all that's left to do (well, almost all) is disassembling and cleaning the keyboard from the filth accumulated in ages.

Then I'll hunt down a proper oscillator for the serial ports, try ADTpro, and finally dig up my copy of Leisure Suit Larry for Apple II.