CPC booting with bad GND.

[arnoldemu]

I have a PC power supply with power leads I made myself.

I have a CTM644 lead which has been cut and connected to a  4-pin power connector plug which I connect to the PC power supply.
This used to give me the 12V for the disc drive, 5V for the computer.

I then had a CTM644 lead which has been cut and connected to a DIN plug for a Plus monitor.

So CPC into PC power supply, screen into a Plus monitor. Power from plus monitor is not used.

I found today that the GND on one of my connectors was not always giving a good contact.
How can the CPC boot with a poor GND connection?

[Munchausen]

Most likely explanation is that the display (signal) ground is shared with the supply ground. But I didn't check the schematics... I'm sure someone else will know the explanation for sure

[Bryce]

The GND in the Monitor connector would be at it's limit, but it would be enough to get the CPC to work.

Bryce.