r.lagendijk_at_hccnet.nl
Date: 2006-06-21 20:55:25
Op Do, 15 juni, 2006 7:09 am schreef William Levak:
> On Tue, 13 Jun 2006, William Levak wrote:
>
>
>> Date: Tue, 13 Jun 2006 14:11:58 +0000 (UTC)
>> From: William Levak <wlevak@sdf.lonestar.org>
>> Reply-To: cbm-hackers@ling.gu.se
>> To: cbm-hackers@ling.gu.se
>> Subject: RE: Help needed with PET 2001
>>
>>
>> On Mon, 12 Jun 2006 ruud.baltissen@abp.nl wrote:
>>
>>
>>> Date: Mon, 12 Jun 2006 07:50:56 +0200
>>> From: ruud.baltissen@abp.nl
>>> Reply-To: cbm-hackers@ling.gu.se
>>> To: cbm-hackers@ling.gu.se
>>> Subject: RE: Help needed with PET 2001
>>>
>>>
>>> Hallo Richard,
>>>
>>>
>>>
>>>> It could be that the charROM is not perfect but I don't have
>>>> a 6540 that I know it's perfect to swap.
>>>
>>
>> It looks like an addressing error, address bits 8 and 9 shorted
>> somewhere.
>
>
> There are 4 versions of PET 2001 system board:
> 6540 or 2316B ROM's
> 6550 or 2114 RAM
>
>
> There are also several different versions of ROM's.
>
>
> From the above, I see you have 6540 ROM's. What type of RAM do you have?
> The addressing logic is slightly different. What are the ROM part
> numbers?
>
> This is definitely a malfunction on the system board. The pattern at the
> bottom of the screen is typical of addressing problems. The system has
> cleared the first three pages of screen RAM, but has crashed before
> displaying the usual start up message.
Hi,
I've tried to find a short on the PCB but have not found it yet.
I got 6540 ROM's and 6550 RAM's on the board.
ROM part numbers (I hope this is the number below the MPS6540):
H1 = O19 5078 A
H2 = 013 4478 A
H3 = 015 2878 A
H4 = 016 4478 A
H5 = 012 2978 A
H6 = 014 4178 A
H7 = 018 4378 A
A2 = 010 2678 A
I added another picture to the HTML file
http://www.xs4all.nl/~lagendr/Diverse/PET2001.htm
In the last picture I disconnected pin 2 on E9
E9 gives the video signal to the monitor, pin 2 does the "video on"
I have now 8 char-lines on the screen with recognisable characters, so I
think the char ROM is fine. The 8 char-lines are in the middle of the
screen (vertical)
Char-line "1" and "6" seem to be the same. Also it looks like if the lines
are "written" more than one time.
Could it be that the counter that does the 0 to 24 (char-lines) counting
starts at character-line 9 (or about) and goes to 17 (or about) and does
that over and over again. and not displaying the other char-lines
Greetings Richard
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