Re: CBM8296D hangs after reset

From: André Fachat (afachat_at_gmx.de)
Date: 2007-04-22 18:53:01

Hi Michael,

it seems something is flakey in your 8296.

I don't think it is the PLA, although this ICs breaks quite often.
Do you have an oscilloscope or logic probe?

Dou you have known-working replacement ICs to check whether an IC
is broken by replacing it and seeing if the problem is fixed?

Is the startup beep faster or slower than normal when it beeps?

I had a 8296 with a broken VIA 6522 that had some similar problems (booting into the monitor, sometimes with beep, sometimes without.)
You may want to check that one first.

You can check this page, it includes links to diagnostic manuals and a page for PLA replacements.
http://www.6502.org/users/andre/petindex/repairs.html

André

-------- Original-Nachricht --------
Datum: Sun, 22 Apr 2007 17:20:11 +0200
Von: Michael Huth <enigma@mail.lipsia.de>
An: cbm-hackers@ling.gu.se
Betreff: CBM8296D hangs after reset

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> Hash: SHA1
>  
> Hello,
> 
> after about 1.5 years I tried to reactivate my 8296D, but it seems to
> hang now after switching on / or reset.
> It worked previously.
> 
> The error looks like this:
> The screen stays black and the CPU seems to stop at some point.
> Most noticeable when the startup sound stops with a permanent sound.
> The floppys seem to reset ok.
> Once I had the screen full of chars, that looked like memory after a
> power-on.
> Once it stopped in the Monitor and when I entered 'x' it showed ready.
> and hanged.
> Once it stopped in the Monitor and the cursor ran forward producing
> random chars, when I pressed shift-clr/home it cleared the screen and
> hanged.
> If I press reset short, it seems to stop in most cases before the
> startup sound is played.
> If I press reset for about one second it plays the full startup sound.
> 
> I took out and in all socketed ICs, to see if it a contact problem,
> but it didn't helped.
> I noticed that UE6 gets quite hot (so hot you cant keep your finger on
> it for some time - if you arent a cook ;) ).
> 
> I read in some forums that this error might be a defect PLA (UE6) ?
> There was also written, that somewhere a reverse engineered ROM is in
> the works, but I couldn't find any.
> 
> So could this error apply to UE6 and if so, where can I get a replacement?
> 
> Ciao...
> ...Micha
> 
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