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From: binder@asd.DEC.COM ("Exit, pursued by a bear")
Newsgroups: net.micro.apple
Subject: Re: ][+ w/munged memory
Message-ID: <8610152235.AA02391@decwrl.dec.com>
Date: Wed, 15-Oct-86 21:13:00 EDT
Article-I.D.: decwrl.8610152235.AA02391
Posted: Wed Oct 15 21:13:00 1986
Date-Received: Thu, 16-Oct-86 00:05:45 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 52

Boebert@hi-multics.arpa writes:

> My ][+ has the following hard memory failure:  at locations 8000 and
> above, the monitor commands
>
> *8000:  00 00 00 00 00
>
> *8000.8004
>
> results in a display of
>
> 40 40 40 40 40
>
> and similarly for other entered values (i.e., 01 -> 41, etc.).

The failing chip may be one of three.  Take the cover off your Apple and look 
at the RAM area, which is enclosed in a big white box toward the left side of
the motherboard.  At the left end, in IC locations C1, D1, and E1, are three
14-pin configuration jumper blocks.  Pin 1 is at the lower right corner, and
the pin layout is like this: 

           +-----+
	8 =|     |= 7
        9 =|     |= 6
       10 =|     |= 5
       11 =|     |= 4
       12 =|     |= 3
       13 =|     |= 2 
       14 =|    o|= 1
           +-----+

Look at pin 8 of any one of these jumper blocks (they should all be the same),
and see what other pin it's connected to.  If pin 8 is connected to pin 14,
then the failing chip is in location C9.  If 8 is connected to 13, the failure
is at D9.  If 8 is connected to 12, the failure is at E9. 

(I've assumed you have 48K.  If not, then you have 36K, and you should look at
pin 7 instead of 8 in the preceding description.)

Before assuming that you have a bad chip, try reseating the chip in its socket
in case the problem is merely poor contact.  If that fails, try swapping the 
suspected chip with the one to its immediate right (C10, D10, or E10) and see
if the monitor reports that $00 has become $80.  If so, you have a bad chip. 

	*** Do all this reseating and chip swapping with power OFF! ***

Cheers,
Dick Binder   (The Stainless Steel Rat)

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