Re: C64 to C64C mobo conversion

From: Gerrit Heitsch <*gerrit_at_laosinh.s.bawue.de*> Date: Fri, 24 Jun 2022 06:46:37 +0200 Message-ID: <56f34c65-3242-79be-ff97-a05658bb15ae_at_laosinh.s.bawue.de> · gerrit_at_laosinh.s.bawue.de

On 6/24/22 03:26, tokafondo_at_tokafondo.name wrote:
> I have a pre-8701 C64 motherboard and a C64C motherboard.
> 
> If I wanted to test 8580 and 8563 chips in the C64 motherboard, would it 
> be just enough with replace the 7812 with a 7809?

No, the VIC from a C64C expects 5V on Pin 13. You can get that from Pin 
40, but it's a good idea to run it through a ferrite bead and put a 
100nF capacitor between Pin 13 and GND.

Also, you might have to rework the modulator since the 856x VIC expects 
a 1kOhm pullup while the 656x VIC wants a 500 Ohm pullup on the luma 
signal. This pullup is found inside the modulator. Just replacing the 
VIC might result in a dark video signal.

  Gerrit