UK-101. Where does clk o1 come from.

[acollins22]

Hello Folks,

I am trying to get my old UK-101 running and there is no clock on pin 37 of the CPU.

I can see it going into the clock tree of dividers but can't see how it gets to pin 37 on the 6502.

Can anyone shed a little light please?


Thanks,

Andy

 

[Robbbert]

According to the manual, crystal X1 (8 MHz) uses 2 gates of IC58 (7400) for the oscillator, the output then enters pins 1 & 2 of the same chip and comes out at pin 3. This signal goes to IC29 (7493) at pin 1 and is divided by 8 to give 1 MHz at pin 11. This apparently goes directly to pin 37 of the CPU (and many other places).

 

[acollins22]

Thank you Robbbert,

I has missed the branch on that line from IC29. I scoped it at both ends and there appeared to be a break between IC29 and the 6502 so I flipped the board over and a previous owner had broken the track and routed the clock signal to a pair of connectors on the back panel that had become disconnected.

I have connected them, prior to removing the mod and it is working now.

Thanks again,

Andy.