Problem with 4066BE and Crystal Signal.

Thread Starter

rafael1138

Joined Feb 17, 2024
1
Hi, I'm not electronics expert but wnat to try to figure out a solution to an issue I have.

I have a custom Commdore 64 board, it works fine. This board has 2 modes, NTSC and PAL. For this, the board has 6 jumpers that require to be in an specific position to work in NTSC/PAL mode (The green jumpers):

IMG_4823.jpg

Each jumper carries an specific signal or voltage. (1v, 5v, 12v, signals)

Because I don;t want to open the case every time I need to change the mode I made a switch solution, the thing is, I have used SPDT switches, 2 channels, so I ended with 3 of them for the 6 jumpers:

IMG_4826.jpg

I wanted to have only 1 switch to change all of them at once. I believe there is no a 6 channels (18 pins) switcher, maybe I'm wrong, but someone recommend me to use a 4066 IC, so I did a test and all works except when I try to switch the Crystals signals.

There is a switch that requires to join Pins 1&2 for NTSC and Pins 2&3 for PAL. Pin 1 = Ntsc Crystal signal, Pin 3 = PAL Crystal Signal, Pin 2 = Pin that connects Crystal signal to the Clock Input.

1708217388432.png

If I test the switch with only 1 signal in the IC, it works, the problem happens when I add both signals.

So I added in the 4066
Pin 1 = Pal Crystal Signal input
Pin 2 & 3= Line to clock input
Pin 4 = NTSC Crystal Signal.

To me looks like for some reason, when I join Pin 2 & 3, that is common for both switches, the whole things fails.

Do you know if there is an easier and efficient way to acomplish what I'm trying? Maybe a different IC?

Thank you.
 

MrChips

Joined Oct 2, 2009
30,779
Quartz crystal oscillators are very sensitive to capacitance effects. Any long wires from the crystal to the CD4066 would cause it to stop working.

Yes, you can do it with a single toggle switch.

1) You need to examine, reverse engineer, or get the circuit schematic and see what all the jumpers do. You can build a data selector circuit to satisfy those requirements.

2) To switch between the two crystal frequencies, you can either have two separate CD4066 circuits (i.e. add another CD4066 circuit), or you can build two separate crystal oscillator circuits and then select which oscillator feeds the CD4066.
 
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