Re: Faulty RAM on Apple IIc motherboard

[ralphp@gcstation.net (Ralph Wade Phillips)]

Hi, Mitchell!

In article <25JUL199603103854@vax2.concordia.ca>, spec@vax2.concordia.ca
(Mitchell Spector) wrote:

>    An Apple IIc (ROM 0) I bought the other day seems to have defective
> DRAM chips on the motherboard. They're soldered-in of course, so I'd
> like to know _exactly_ which chips need to be replaced. Conducting the
> built-in self-test reports back the following:
> 
>      *RAM ZP 0 0 0 0 0 0 1 0 0
> 
> (I know the 1's are 'bad' chips, but which end would that be on and
> what is the "ZP"? Which of the sixteen 8K DRAMs are at fault here?)
> 
> Mitchell Spector
> spec@vax2.concordia.ca

        ZP says that the //c failed RAM test in the Zero Page (i.e., the
first 256 bytes).  That's rather drastic (sigh).

        Bank 0 (the first bank) is towards the front of the computer, Bank
1 (the one I remember this form of the error message identifying) is
towards the back.  The rightmost character is the backmost chip.  The
"1"'s ID the defective chips.

        I !MIGHT! be wrong.  One thing you can TRY is to clip a spare 4164
over the suspected RAM chip (a sacrificial one).  And, try leaving it on
for about 4-5 minutes with the cover off.  See if one RAM chip gets
noticably warmer.

        RwP

-- 
Ralph Wade Phillips, CET #LA-82
ralphp@gcstation.net