Re: IIe faulty RAM ?

["Mark Cummings" <NOTfigjams@primus.com.au>]

> Pull all the cards from your IIe and attempt a start up.

Yes I did that too, but the fault is identical, so I put the drive
controller and 64K/80col card back. Both are known servicable anyway.

> If you do NOT get the Apple II message at the top, you may have a Power
> supply issue.    Swap in a known good power supply and start your tests
> over again.

As I stated this is a known good power supply, and I did try another supply.
Also tried the original supply on another board and it was fine. It _IS_
down to the motherboard, no doubts at all !

> If you get the Apple II message at the top, press Control Reset and see
> if you get a basic prompt.

As stated I usually get 99% garbage, but after a little time it occasionally
gives an Apple ][ at the top and a prompt, along with a shed load of
flickering garbage overlayed. As soon as I hit a key it sort of locks me out
again, probably due to faulty memory in Page 2 where the input buffer is.

> If you get a basic prompt, press Solid-Apple Ctrl-Reset to run the main
> board self test.

Occasionally I can get a RAM ZP 0 0 1 0 1 1 1 1 or similar message along
with garbage and flickering. The position of the 1's and 0's in the RAM ZP
message alters every time I see it. I also see an MMU message occasionally.
As far as I can tell the test routines cannot run properly because they are
likely trying to use ZP or the Stack for some of the loops. As that memory
is faulty the tests don't last before bombing out. I was considering
swapping the RAM IC's over to proove this, but since they are soldered I was
looking for a second opinion first to save a bit of heartache in removing
the IC's.

> If the main board fails in some way, you will get an error message.
> Refer service to a qualified professional, or see about getting a
> replacement main board.

I am a qualified professional, just after some local Apple IIe knowledge and
experience with RAM faults. This is the first IIe I have ever seen with a
faulty motherboard. I have 5 IIe's, one is a non-enhanced model that I
upgraded myself. Two of them had faulty power supplies, I fixed those, now a
motherboard failed and the IIe Reference manual I have has a circuit for a
non-enhanced IIe, not the Platinum model which is greatly down on chip
count. This circuit is not much help on the newer model. As far as a
replacement is concerned, this is a "spare" board as I stated. If I can fix
it, it'll only be for the fun of it. Then maybe someone will pay me a lousy
$1 for it, even though the RAM will cost me more. Like I said, this is for
the fun/experience, if someone else fixes it, I don't have any fun, nor do I
get any experience.

> If the the test comes back with Kernel OK message, then place the 80
> column card in and restart the computer.  Keep adding cards one at a
> time and restarting until the computer fails.  The last card put in
> should be the culprit.  Of course sometimes cards fail only when paired
> with another card, good luck finding that.

It's NOT a card, see above. BTW: The message is "System Good", not "Kernal
OK".

thanks Ed, no offence, but I put a stack of info in my first post to cut
down the generic answers.

BTW: I did get a personal reply from someone that has had similar
experiences with faulty RAM, and the symptoms I stated are typical of that
fault. He has managed to fix a few IIe's with just these RAM faults, so I'd
say this is a common motherboard fault. Wheras the IIe power supply has C7
as a common fault.

Going back to my II+ days, when I knew jack about computers or electronics,
I made friends with a guy that worked for an Apple distributor as a
technician. The II+ I purchased had about 7 or 8 bad RAM IC's that failed
within about a week of my purchase. He showed my the in's and out's of
testing for faulty RAM in those models. A hair dryer and a can of freeze
spray were handy for that. Another technique that works well is to place the
suspect IC's in a particular row of 8 (centre one I think) on the
motherboard and boot it, then type HGR. The bad ones would show up as
vertical lines on the screen. This was a piece of cake to master. He gave me
about 8 spares so if it happened anymore, I could have a go myself. The only
problem with applying this technique on the newer IIe and platinum IIe's is
that the RAMs are soldered to the board (to increase reliability). In those
days some of the sockets were pathetic single wipe styles. These days dual
wipe or machine pin are far more reliable. I wish they had stuck with the
socketed chip policy, particularly when it comes to CMOS RAM, which is very
susceptable to static damage.

Mark