Path: utzoo!attcan!uunet!husc6!bloom-beacon!mit-eddie!ll-xn!ames!pasteur!ucbvax!MITRE-BEDFORD.ARPA!jhs
From: jhs@MITRE-BEDFORD.ARPA
Newsgroups: comp.sys.atari.8bit
Subject: 130 XE Service problem
Message-ID: <8805171542.AA12361@mitre-bedford.ARPA>
Date: 17 May 88 15:42:14 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 40


>       I have a 130 XE machine, that will not allow one to do
>       anything except watch the RAM test in the self help
>       diag's text. It goes there right off. Once in a while one
>       can press RESET and get the machine to Basic, but after
>       hitting Return, major Lock-up.
Since the PIA is the chip that selects the self-test ROM, I would check
the PIA first.  Look at the logic line from the pin (I think it is Bit 7,
the Most Significant Bit (MSB)) to see if it is asking for the diagnostic
ROM (I think that would be a LOW output instead of +5 volts).  Also check the
logic chips that this bit controls.  One of them may be burned out, causing it
to command the diagnostic ROM into action even if the PIA is not telling it
to.  I suspect you will find the problem to be either a bad PIA or a bad
gate driving the ROM chip select line.

>       Have tried the OS chip, wish another, and even my Omni view,
>       along with the Antic, the Salley and MMU (6161) all to no
>       avail. These seemed to be the place to start, but all yeild
>       the same problem. I was going to try the PIA chip, but think that
>       this would yeild the same, and really don't like de-soldering
>       40 pin chips. I can think of more pleasent things to do ;^)
Given the symptoms, the circuitry from the PIA to the O/S ROM is the probable
location of the problem.  Save all those parts you changed, 'cause they are
probably perfectly good.  Since you changed the MMU, I suspect it is, after
all, a bad PIA chip.  The only other thing I can think of is a short across
the lines from the connector where the keyboard plugs in.  Hah, that's
eliminated by the fact that both OMNIVIEW and the Atari chip come up the
same way.  Since they react oppositely to the OPTION key, it can't be just
a short that makes it look as if the OPTION key is being held down.

>       Any help would be appreciated, as this one has me scratching
>       my head.
It would of course help if you had a 130XE schematic diagram and a 'scope
or at least a VOM (Volt-Ohm-Milliameter).  But the more I think about it,
the more I think it is probably a bad PIA.  Either that or a fault in the
wiring to the PIA, like a solder splash that shorts a pin to ground.

Good luck.

-John Sangster / jhs@mitre-bedford.arpa