Re: option ROM into a 3032

From: Francesco Messineo <>
Date: Fri, 29 Sep 2017 10:20:58 +0200
Message-ID: <>
On Fri, Sep 29, 2017 at 7:55 AM, Francesco Messineo
<> wrote:
> On Fri, Sep 29, 2017 at 7:05 AM, William Levak <> wrote:
>> On Thu, 28 Sep 2017, Francesco Messineo wrote:
>>> On Thu, Sep 28, 2017 at 12:48 PM, Francesco Messineo
>>> <> wrote:
>> If you have an older PET (without CRTC) that has been upgraded to Basic 4.0,
>> the jumpers may not have been set correctly.  There are jumpers that
>> control addressing of the ROMs. If they are not set correctly you will have
>> addressing problems. Check the schematics for correct jumper settings.
> Yes, I was just going to check that. I've noticed the jumpers don't
> match my 3032 (with older basic). The owner of this PET said it used
> to work though, so I was assuming that the jumper were correct.
> I will also change the timing resistor and tantalum capacitor on the
> 555 reset circuit, I've noticed the reset signal isn't very well
> behaved (it resets randomly and sometimes doesn't release the reset
> line). I think the tantalum capacitor is shorting randomly to ground
> or the 1M resistor is intermittent.
> Old hardware sometimes has lots of faults.

update: changing the UD8 socket, did bring the system to the basic
prompt, with correct bytes free count.
I then restored the two CAS resistors (I had lifted them to swap RAM
banks) and now I have a completely black screen, not even the garbage
screen if I remove the UD9 ROM :(
Looks like I now have to debug the video signal path. This PET hates me I guess.


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Received on 2017-09-29 09:00:02

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