Help with repair

[1024MAK]

Sounds like it. But you can still test the resistance of the +5V supply to 0V to see if you no longer (hopefully) have a short circuit.

Thanks for that info Mark, where should I put the meter to test this?

Across any +5V and 0V connections. So across the solder pads of ZD2, or as I wrote in an earlier post:

A good 0V point is either the modulator case, or the ground on the video output (if the lead is plugged in to the MTX video board!), so connect the negative black meter lead to 0V.

and

Test the right hand pin of the 7805 regulator. Resistance should be >300 ohms.

or between the Vcc and GND pins of any of the 74LS series logic chips (links to data sheets are here), plus on many of the other chips like the CPU or DRAM chips.

Mark