Re: IIe faulty RAM ?

[Stephen Shaw <xstephenx@apple2.org.za>]

Mark, the message means there is faulty RAM.

On Wed, 13 Jun 2001 23:56:41 +1000, Mark Cummings wrote:

>> 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

-- 
2 + 2 = 5 for extremely large values of 2.