Re: IIe faulty RAM ?

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

thanks Stephen,

FYI I already posted my findings, and it was the one of the two RAM chips
producing this fault.
Also the built in test will normally fail, because each chip is 4 bits x 64K
and the CPU just cant cope trying to run the diagnostics with bad data on
the bus. In the older II+ I can see that provided the lower 16K is working
that it would likely run some kind of diagnostic from disk. However on the
newer IIe and Platinum IIe design, it is a waste of space IMHO.
I conclude that the best way to know if the RAM is the fault is just by
looking at the screen and talking a guess as to which chip is bad.

This would also apply to a GS, as I also had a RAM fault in a ROM-3 which
exhibited virtually identical symptoms.

Anyone wanting assistance replacing or aquiring RAM chips for the IIe, drop
me an e-mail. I have various spares for both models. Otherwise you most
likely will find them on some old PC video cards.

Mark
Townsville, Australia
remove NOT to e-mail me.


Stephen Shaw <stephen@apple2.org.za> wrote in message
news:9h5239$3di$1@venus.itns.co.za...
> Very likely!
>
> On Sun, 10 Jun 2001 23:30:03 +1000, Mark Cummings wrote:


> > I have an extra Platinum IIe International NTSC motherboard that WAS
> > working and now NOT working.
> > IIe has known good power supply, and 5.25 controller in slot 6 with a
5.25
> > drive connected and a 80col/64K card. Except for the motherboard all the
> > other parts are known good.
> >
> > These are the symptoms:
> >
> > 1. Power on produces No beep, a display full of random text/or graphics
> > which appears to be flickering, and the disk fails to boot. All voltages
> > measured on the motherboard are good.
> > 2. Attempt to Ctrl-Reset freezes display until RESET is released, but
then
> > returns to previous condition but usually with a slightly different
screen
> > of garbage.
> > 3. Attempt at Ctrl-OA-Reset, is pretty similar to Reset, although
> > occasionally I get a noise from the speaker or the disk light goes on
> > (forever, until Reset again). I guess this is just the drive motor I/O
> > location getting some garbage.
> > 4. Attempt at Ctrl-Option-Reset gets treated similarly, occasionally the
> > 80-col display comes on, or a graphics page with similar flickering
> > graphics.
> > 5. Attempt to use freexe spray or my thermonuclear device (hair dryer)
has
> > failed to alter the state of the fault. This was an old trick that I
> > remember using years ago on a II+.
> >
> > I have swapped all the socketed IC's out with another identical working
> > unit, and the result is the same. The chips placed into the other IIe
work
> > fine.
> >
> > I am suspicious of the soldered in RAM, which is 2 of 41464C-10. Before
I
> > go desoldering, can anyone shed any experience with RAM faults and the
> > symptoms.
> >
> > Would the inbuilt diagnostics (Ctrl-Option-Reset) run correctly if the
RAM
> > was faulty, if so how would it display the result, since the text screen
is
> > memory mapped. Also, should it still make any sounds, as this would be
> > addressed outside of RAM space ?
> >
> > One thing I have noticed is that there appears to be some message in the
> > middle of the screen occasionally that looks like R?M something or
other,
> > which I think is a call for help ! :O
> >
> > Mark