Power supply 5v regulator - what's wrong with this picture? (mr. do)

[HudsonArcade]

@TheShanMan - yes I know this is an old post but I am in the exact same boat with my Zero Hour restore. Getting 10V on the power supply. Was going to replace the regulator but maybe that is not the issue. What did you end up doing?

Yes, I have 6 other Universal games but they are all in storage right now so I don't want to pull them out just to see how their power supplies behave.

Lift a leg on the shunt resistor and see if you get 5V.
The regulator itself shouldn't need a load to regulate properly, but the extra shunt current messes it up.

If you're still getting 10V, the reg is prob internally shorted.

 

[HudsonArcade]

The other part of me knows if I fry a Zero Hour board, it is going to be a PAIN to fix it if I ever do and no one really repairs these.

There's nothing particularly difficult about fixing a Zero Hour... Z80 game with the same basic architecture as the other Universals of that era.

For some reason, the notes on my redesigned Universal Boards don't mention Zero Hour, but I haven't looked at it that closely, so it may be a pretty easy addition.
It's listed in the MAME redclash.cpp driver rather than the cosmic.cpp driver, but it probably isn't very different.

The only really nasty Universal is Cosmic Guerilla, as it's TMS9980-based instead of Z80, although the 8080 games kinda suck too.

 

[DZA]

Lift a leg on the shunt resistor and see if you get 5V.
The regulator itself shouldn't need a load to regulate properly, but the extra shunt current messes it up.

If you're still getting 10V, the reg is prob internally shorted.

So I did this and get 4.9V. What would you do

I also ordered the resistors to make the load so I can also test that....

 

[HudsonArcade]

So I did this and get 4.9V. What would you do

I would have swapped in a switcher as soon as I got it, but that measurement at least implies the reg isn't shorted and won't overvoltage your board.

A few years ago, I made up a bunch of switching regulators on TO-3 shaped boards to replace linear regulators, but never got around to playing with them

 

[DZA]

FYI - I built the resistor load @wpmcnamara suggested. The voltage then became ~5V. Between that and the pulled leg resistor check, I was confident enough to plug in the board. No issues. ~4.7V at the board. Booted up. Game works. The monitor just needs some final tweaks

Thanks all!