RE: mosaic screen on c64

Thanks, a friend bought a c64

http://cbm8000.com/IMG_1387_2.png
http://cbm8000.com/IMG_1385_2.png

For now I only have a small image around the 6569...

According to this small image it's either

http://www.c64-wiki.com/index.php/File:C64_PCB_Assy250407RevA.jpg
or
http://www.c64-wiki.com/index.php/File:C64_PCB_Assy250407_Schematic251137Rev
B.jpg
or 
http://www.c64-wiki.com/index.php/File:C64_PCB_Assy250407_Schematic251137Rev
C.jpg
or 
http://www.c64-wiki.com/index.php/File:C64_PCB_Assy250407_Schematic251137Rev
D.jpg

I don’t see enough to tell the differences between these boards..

I've forwarded the questions


Thanks

--
Didier



-----Message d'origine-----
De : owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] De la part de Gerrit Heitsch
Envoyé : lundi 4 août 2014 22:26
À : cbm-hackers@musoftware.de
Objet : Re: mosaic screen on c64

On 08/04/2014 10:02 PM, didier derny wrote:
> Any idea why a c64 can only display a mosaic screen an nothing else ?
>
> Just little colored squares on the entire screen
>
> Any idea ?

Lots of them... But first I would need some information:

Board Assy No?

Voltages are OK?

Any MOS-TTLs on it? Those are the small ICs with a MOS logo and a number
starting with '77'.

Any IC getting hot?

What kind of RAMs does the board use? Maker?

If you could supply a picture of the board that's good enough to be able to
read the writings on the ICs, that would really help.

The usual suspect, unless it's a 250469 board which uses the larg 64pin IC,
is the PLA. If it's socketed, try it in a working board.

And quite often trying the following will give you some hints. You can use
the ROM cartridge without all the wires for basic testing.

  http://ist.uwaterloo.ca/~schepers/diagnostic.html



  Gerrit




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