Every couple of years I get out my old Apple II Plus units (x2) and try to get one up and working. It has been this way for a while- I use one to fix the other, since storage is not good for these old boys.
This time I have many more bad RAM chips (x6), 2 bad 174's (from row 'B') - one causes video to glitch, and the other causes the keyboard to repeat keys forever- why did these die in storage?
Also, one of the units, when good parts are put in, no longer has color. What causes the color to no longer work?
I have no clue about the IC dying in storage. IMHO the Apple II is by far one of the more reliable computer ever built.
By the way, if there is oxydation, you should try to clean the pins and reseat the IC on the motherboard. This trick does sometimes miracle.
For the color problem now, you can try to change B13 (LS02) and B12 (LS11) and see if the problem will go away.
RAM dying in storage seems really strange to me. I have a 10x11 foot room packed about 7 feet high with Apple II stuff from the days when they could be bought at thrift stores for less than $10. Much of that stuff has been in storage since the 90s, including three years in an unheated storage unit while I lived overseas. But, barring power supply and keyboard problems, when I do pull something out, it almost always works. What are your storage conditions like?
As for the color, start with the basics. Does the monitor display color when another computer is hooked up to it? Are you running a program with color graphics? Are you plugged into the video out from the main board or a video out on a card (like an 80 column card, for example)?
Thanks. It is in an air-conditioned basement, so not too bad. These units were well on their way into corrosion when I got them, so it's an ongoing process now. I tried reseating the ROMs last night and two legs just fell off them- they are black from corrosion/age. They led a bad life before I got them, so it's just a matter of time. Perhaps I will try to just replace all the TTL chips from scratch.
Firmware board, 4164 RAM rigged to replace the 4116, any other tips to extend their life? I like the firmware board that Mike sells since it has the Apple I personality- that is really neat. Does anyone sell a board that just replaces all the motherboard RAM with a couple of 2464's instead of 24 chips?
The monitor displays color on the other A2, and it is plugged into the standard composite out on the back of the A2.
BTW, my other A2 is almost always in color- the killer circuit doesn't seem to work 99% of the time.
Thanks, but that didn't add color output.
After swapping every chip in the video circuit, I swapped the crystal. Now neither A2+ has color.
I guess the crystal is very finicky and is now damaged from heat or something.
If everything else is working, but you don't have color - most likely one of two problems.
1. color burst circuit is broken - this is pretty simple and just takes the color burst clock and adds it to the video signal during part of the video retrace. The so called color killer transistor attempts to kill this clock when in text only mode.
2. the crystal is out of tolerance. The crystal has to be right on the money or a color TV will not be able to lock to the color burst. The only replacement I've found that works reliably in the Apple II circuit is: vishay/dale part # XT9UNLANA14M31818
Thanks very much, Mike- I'll see about getting one of those crystals and see if it helps. I replaced one with one from a C64 (14.318) but no color.
New crystal fixed the missing color on both boards. Thanks for that- I never would have thought it would cause no color with no other visible symptoms.
Now, there is one more problem. The machine passes all diagnostics and plays most games fine, but I noticed it will *NOT* play Skyfox. It get to the title screen and runs a few frames, then freezes the computer. I figured this game needs the language card (64k) and that may be bad, but it works fine in the other II+.
Is there a known issue with Skyfox? Where would I look for a board problem affecting that one game (that I know of).
Same disk card, same language card, just different board.
well you can always try popping in the language card from the working II+ and trying that out and if the game runs fine then theres your problem. Ofcourse when you put the bad card in question into the good II+ and try the game , and if it mimicks the problem well thats that.....
Already tried that- it's not the language card. Something else subtle is wrong, I suppose.
For the record- I had some crystals that worked, I didn't order the ones above.
Markings on side are:
Oki Doki..... Let us know what the fix is...