Re: 2001 repair help

From: Francesco Messineo <*francesco.messineo_at_gmail.com*> Date: Wed, 27 Dec 2017 20:30:33 +0100 Message-ID: <CAESs-_zaM82fCd90SX9V7NJd-MJT_tdmM0-cXSgi1hJ6zgxf6w@mail.gmail.com> · francesco.messineo_at_gmail.com

On Wed, Dec 27, 2017 at 8:18 PM, vossi <vossi@ceffy.de> wrote:
> Normally at this boards the half of the 6550 and some 6540's are dead...
> Often the 6520 are faulty too.
> The sockets are a very big problem. Commodore used in the old 2001 the high
> black sockets with metal outside - these are very bad! Also they have not so
> high sockets with metal contacts inside - these are much better. And they
> used TI-sockets with very thin holes - these are the best!.

yes, I'm making an external test set to check all the 6550s one by one.
As for the 6540, I haven't decided if I want to make a similar setup.

>
> I have a rom-replacement board that fits in H2 to H5 as 6540 replacement.
> And I test the RAMs and ROMs with my 2001TEST in H7 (with adapter 27xxx to
> 6540). You find it here: http://lc64.blogspot.de/2016/10/

Thanks for the pointer, I will surely give it try!
Do the 6540 really need a running clock or the phi2 input just needs
to be in the high state for the ROM to be selected?
I was hoping they could be read on a standard EPROM programmer with a
bit of glue logic.

>
> Poking and peeking to $8200 worked, but on the screen is still a wrong char.
> That was because the screen-display-counter D7 74177 has probs with the jump
> to the highest bit.

nice find :)

Frank

       Message was sent through the cbm-hackers mailing list