Re: 6561-101

The problem is that this is my first ever VIC20 so I have no cartridges... 
The idea is however good.
Thanks
Hege


-----Original Message----- 
From: Clockmeister
Sent: Wednesday, October 26, 2016 3:00 AM
To: cbm-hackers@musoftware.de
Subject: Re: 6561-101



On 26/10/2016 4:38 AM, Hegedűs István wrote:
> Hi,
>
> It has black screen of course. I know that the Kernal ROM or VIC used to 
> be the guilty ones. I have burnt a 27c128 with Kernal but still have to 
> build an adapter so I cannot 100% rule out Kernal issue. The guy who sold 
> it said that the 6502 is also sick (he has tried the CPU in an 1541), 
> though with oscilloscope I have seen e.g. proper phi2 signal coming out. I 
> have bought some Rockwell 6502s to replace it. Anyway even if it turns out 
> that VIC is good it is better to have a spare IC.
> I should hook up my logic analyzer to it but so far I had no time (or I 
> was just too lazy).
>


Whilst mask ROM (and RAM for that matter) failures are common on vintage
equipment, the last two VIC-20's with a black screen that I repaired had
a bad 6561-101.
In my case both were easy to diagnose by simply plugging in a cartridge
or blind loading a game. On both occasions the game you could hear the
game playing even though there was a black screen.





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