Re: mosaic screen on c64

From: Gerrit Heitsch <>
Date: Mon, 04 Aug 2014 22:25:57 +0200
Message-ID: <>
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.


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Received on 2014-08-04 21:00:02

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