Ahem,...
The 424mkII has an attached AC power cord, and no "module", as such.
Given that you plugged it into a viable power outlet,... which should be verified,...
I've opened up the 424mkII before, and looked for a fuse, but did not find one. However, it's my gut feeling that there is a main power fuse, and I just did not find it. I think if I were to look again, I'd probably find one.
Y'know, it depends on your DIY skills, when it comes to opening up a Portastudio. There's nothing incredibly difficult about it, but you have to have a minimum baseline of DIY repair skills. In this case, a volt meter would help.
I'd suggest, if outlet power has been verified, to maybe open up the unit, and inspect the power supply section for a fuse, and determine if any fuse is blown. Beyond that, you're pretty limited, but at most you could poke around in there with a volt meter to test for voltages.
Of course, at the point of disassembly and inspection, the unit should be unplugged. If you venture to the point of actually testing voltages, it should be done only with the most extreme care. I'd not recommend power-on testing if you're not moderately skilled in electronic repair. Lethal voltages present.
If you could locate a fuse, that's a no brainer, but anything beyond that might be best referred to a trained service techncian.
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