Has this clock ever had working high voltage? I just re-read the entire thread and it's not clear whether it ever worked.
Also, can you try a different power supply? The problem you are having now may be as simple as the power supply - which I already said was of marginal size - is cutting out under load. Power supply should be capable of 500mA or more.
If the same thing happens with different power supply I guess we are headed for a big troubleshooting exercise. For that, a good quality photo of the solder side of the board would probably be helpful.
Look into it later when the dust is clearing off the crater.
Is it ok to use a 2.5 ma 12v power supply? The clock was working but every time I powered it on I had to touch the mosfet to get the tubes to light up so the mosfet eventually broke, that's why I rep!aced it.
The power supply must be 500ma (1/2 amp) or greater. The voltage can be anywhere from 7.5v to 12v. Less than 7.5 volts risks running too low for the inline regulator on the board to maintain the 5v that is needed by the CPU. More than 12v will generate more heat than can be dissipated without additional heat sinks.