Hey guys, maybe you can help me out on this:
One of the apple iie computers I originally bought had a RAM problem which prevented it from turning on. It just gave garbage when I attempted to do so. I replaced all of the RAM chips and the problem disappeared. I also got an Apple iie enhancement kit and now the iie is enhanced.
This iie passes the diagnostic tests (the one where you hold down the apple keys and turn the computer on).
So I boot up one of my favorite games, Destiny.
No matter which good and aligned joystick I hook up to the computer, the pointer on the screen moves painfully slow whenever I try to go downwards or to the right.
Whenever I use my other Apple iie computers and do the same thing, the speed is normal.
What could this bizarre problem be?
Hello Insanitor,
take a view to the schematics of the Apple IIe and take a look to the NE558 ( marked at location UA12 ).
Its related to the Joystick / Paddle connector.
Within that path there are 4 capacitors:
C34, C35, C40 and C37. They are 0,022µF or in other notation: 22nF.
It seems that one or 2 of them are damaged.
In order to make sure that you get rid of the problem i´d advise you
to change all 4 of them. They are normally very cheap
- and should cost less than a dollar per capacitor.
that should remove the problem. If not the second
task would be to replace the 4 resistors R21, R22, R23 and R24 ( each 100 Ohm ).
The may be also calculated less than a doller per unit.
sincerely speedyG
insanitor,
This is only happening in the one Apple IIe, but not the others.
I would hazard a guess and say that there is some sort of problem either:
1. at the connector for the joystick or
2. On the motherboard in the circuitry for that connector.
I could be wrong, but I would think if you have no problems with that stick on the other computers
you can narrow it down to those areas.
Steven
Well, Speedy.
This time with your help, I was able to fix it.
As soon as I replaced those 4 capacitors, the computer booted and the joystick problem disappeared.
But then I had another problem.
When I would reboot or at random times, the computer would go into diagnostic mode.
At the end of the test, the computer would only say, "MMU".
I looked at the motherboard and found a chip on it that said, "MMU" so I replaced that chip.
After I did that, the new problem disappeared.
I really wonder... What is that chip for? Why did it fail?
Hello insanitor,
MMU is the abreviation for Memory Management Unit .....
its one of the large 40 pin custom chips, that is responsible for handling the access to the banks of the RAM
and ROM chips.
You schould bear in mind the adressing habits of the Apple II and IIe.
It also has reserved space of adressing the paddles and the joystick.
So it seems that the one mistake was masking the other problem. At the moment
the joystick problem was solved, the other problem that was lurking disguised
behind that other problem jumped upfront screaming "here i am"....
The reason of failing might have been related to timing issues ....
the capacitors are also related to the timing of the joystick and the
time availiable for the conversion of the voltage. You must bear in mind that the
558 is in a special kind of way a sort of timing chip ( in fact several Monoflops that
are determined in their timing to the 4 capacitors at the gates and the "Master-Timing"
of the 5th capacitor close to the chip.
sincerely speedyG
Yeah, it seems that a lot of my hardware likes to say this to me.
Here's another problem:
One of my joystick's pots are too damaged from wear. It must be replaced. I ordered another used joystick from Ebay. I hope that at least ONE of those pots inside can be used! It was the only joystick of the same model which has some kind of damage and could be used for parts so I ordered it.
I just hope that this time I am lucky.