Warm CPU, no heat else wear, dead cpu?

[inabityo]

I have 3 Famicom motherboards, all of which have no output on the AV mod.

When powered in, the CPU shows a temp of around 55c so not too hot, but no heat elsewhere in the board.

Is it simply dead CPU, anything else we can try? We don't have an oscilloscope. But if reset is low, would that prevent boot?

What can I check without an oscilloscope that might help?

[Skawo]

Even with a dead CPU, you should get a gray screen.
No signal would indicate dead PPU, no clock, or no voltage in general.

I'd check your AV mod work, weird that all three boards would show nothing.