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So I've had this Apple //e problem board for some years now. The board itself has some really bad sodering on all the RAM sockets, as well as the sockets for the EF-ROM and the S02. The fist RAM chip has a lot of bodge work (one of the pins seems to be free floating even) but as far as I can tell, everything is connected to what their supposed to be. The 'new' sockets appear to be double swipe, so decent quality. However, it still won't boot.
I've gone over all the sockets, swapped all the major chips (CPU, MMU, IOU, ROMS) with my other working //e's, replaced all the RAM with new old stock (admittedly Apple branded MT 4264s, but they test good in other machines). Actually, replacing the RAM made a big difference, since before the board would either give garbage screens or not boot at all. Now it's consistanty giving the Horizontal bars every time it gets power.
I know I'm missing something (obviously since it doesn't boot), but what?
Fixed! Dirty socket or glitchy EF-ROM (best guess since the old chip seemed to be fine in other boards) replaced RAM again (found another set in my parts bin). Gave it another clean and reflowed some of the more questionable solder joints. Yet another alcohol bath, and... IT'S BACK!!! Hope this helps someone else down the line with a similar problem. Wish I could say just what it was that tipped the scales, but I have no idea.
a bad capacitor somewhere.
But bad solder joint or dirty contacts would also do it.
OK, sorta fixed... Overall, the computer boots, loads programs, passes self test, and preforms very well, but with one small exception. The joystick (a 9-pin CH Mach III I believe) isn't being recognized properly.
MECC Computer Inspector isn't recognizing anything connected to the port (I also tried a set of Apple branded 9-pin paddles, and a 16-pin Mach III as well). In games (Centipede, Star Trek SOS), the stick automatically goes to the lower-right corner, but does respond to input from the stick.
I've tested both the stick and paddles on 3 other //e's and a //c and it works perfectly with all 4 computers. MECC Computer Inspector reads the stick as slightly off center (jumps back and forth by a pixel or so every 15 to 20 seconds) but it's not enough to effect game play. So I'm pretty sure that it's not the joystick.
I suppose I could just accept that this thing won't be a gaming machine... But then, this thing is so close to being fully functional, why give-up now? If anyone has any ideas, it would be very much appreciated.
You can try to replace the NE558 at A12 and/or the 74LS151 at C12. They are used to read the joystick position and buttons.
I'd recommend a couple of books you can find here:
https://commodore.bombjack.org/apple/apple-books.htm
Apple II Plus IIe Troubleshooting & Repair Guide
How to Repair and Maintain your Apple Computer
SAMS Computerfacts (CC10) Apple IIe
Those may help you diagnose and fix any further issues with your //e.