Re: Apple //e Problem

[rubywand@swbell.net]

Tom31656 writes ...
> 
> .... I had managed
> to scrounge up an 80-column card and a Disk ][ drive, which I know to
> work correctly. I put the 80-col card in first, then tested it. Worked
> fine.
> Then I hooked up the disk drive, stuck a disk (which I know to work) in
> it, and tried booting it.
> 
> After some whrrrr from the disk drive, I got the message "I/O Error" on
> my screen. I know the drive and its card work fine, too. So I performed
> the Apple //e ROM self-test. (Ctrl, Open-Apple, and Reset)
> 
> It flashed only one pattern on my screen, and then displayed the
> cryptic message:
> 
> RAM 0 0 0 0 0 1 0 0
> 
> Turning off the computer, I looked inside at the RAM chips. My
> assumption is that the message refers to the position of a buggy
> RAM chip. The sixth one (counting the odd chip to the far left)
> is a Texas Instruments chip, while the rest are good ol' Apple chips.
> 
> Is this my problem, or is something else wrong with it?
> (Note: My dad got this //e from our school when they "upgraded"
> their computers...perhaps the goof-up is their fault) 

     If the mem IC is defective, it is odd that whoever went to the bother 
of locating and replacing the earlier occupant of the socket did not just 
swap in chips until the problem was fixed.

     Try popping out the TI chip and swapping it with a mem IC one position 
to the left or right. Then, turn ON the computer and repeat the self-test. 
If the error display shows that the bad bit has moved to the TI chip's new 
location it is a pretty good indicator that, at least as far as working in 
your IIe, the chip is defective.

     If the system checks out "Okay", it may mean that the chip just needed 
to be removed and re-inserted to establish good contact.

     If the error display shows that the same bit is faulty, then, it's a 
pretty good bet that the problem is related to lines, probably address 
lines, going to the socket. For example, the socket may have a pin which is 
broken inside the socket or at the motherboard. Or, a solder connection to a 
pin may have fractured producing intermittant contact.

     A problem such as the above would explain why the machine has a new TI 
mem chip and yet remains un-repaired. Pulling the motherboard, checking 
continuity of socket pins to motherboard traces, and, if necessary, 
replacing the socket is a job for a dedicated ][ user.   


Rubywand