Re: Interesting test tools

From: Ethan Dicks <>
Date: Thu, 29 Apr 2010 09:59:49 -0400
Message-ID: <>
On Thu, Apr 29, 2010 at 8:53 AM, Anders Carlsson
<> wrote:
> I duplicated the five images here:
> Somehow, I'm sure Ruud has seen those before... :-)

I have a couple of those myself.  I've reverse-engineered the PCB
inside to about 95% (I think there are one or two signals I need to
check before I call it complete).

Essentially, these boxes have a local ROM that overrides the
motherboard ROMs (I think the circuit forces the bus to read ROM
addressed at $9xxx rather than $fxxx to capture the normal 6502 reset
vector transaction).  To diagnose your PET, you typically plug
loopback connectors onto the user port and the keyboard connector...

...and clip the box on the CPU, then power on the machine.

Here's a scan of the manual...

(I think I have a copy of the tape mentioned in the manual - I'll
check my PET documentation shelf).

AFAIK, there is no substantial difference between the various "models"
of clip, just different firmware (there might be a 2K vs 4K variety,
though).  I also have a few ROM images for 60Hz machines.  We should
create a new section on to collect these files.
Reproducing these boxes would not be difficult at all - the only
expensive part would be the 40-pin gompers clip.


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Received on 2010-04-29 15:00:10

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