Congrats on your purchase. The batteries have failed, corrosion on the battery holder, or has no batteries installed at all. Can you post a picture of your CPU board? I would go with NVRAM to forget about batteries since it is plug and play on this machine. https://www.pinitech.com/products/6264_nvram.php

You can open the coin door and close it to get it in attract mode, if you have all 6 balls in the game, and play it even with this failure. Though, you would be going through this every time you turn on the game until you have good battery voltage or install NVRAM. If you want to stick with batteries, go with Lithium batteries, stay away from alkaline ones since they have been known to leak often and sooner than expected.

You may get lucky to get it past the "open the door" message if you turn off and on the game fast 2 times. If not, you will have to drill the lock to open the coin door.

It would be good if you post a picture of the CPU board for another set of eyes to be sure there is no battery corrosion.

There are 2 solder tabs on the right side of the battery holder on the middle and bottom pins where it is soldered into the board. At least there you should be able to tell if the voltage made it to the board.

Is the game in attract mode, as in the insert lamps are blinking throughout the playfield?

That sounds good. Take voltage readings on the top right of the power supply..5v, 12v, and -12v.

12 volts sounds a bit too low for not being in attract mode. Sure would like to see a picture of that power supply as well. If it is an original board, I would change the capacitors on fhe board.

Yes. It should work fine. Seems your capacitors need to be changed on the JP power supply. Need to consider doing the same for Tommy as well in the near future too.

Basically, the power supply from the standard size 128x32 DMD game is compatible only with those style games, which are what you have now between JP and Tommy. Large size DMD power supply will not physically at all in either of the other 2 DMD sized games.

I am hoping t hat you can measure the 12v on the Tommy power supply before you oull it.

This is why I like seeing pictures of boards when someone has battery leakage. Need to see how bad it is. Hopefully, only a new socket and NVRAM will take care of it, if there is no other corrosion anywhere.

Do you have the original JP power supply in it now or the one from Tommy?

I'm still waiting to see a picture of the MPU board.

ChrisHibler would be happy to give you an estimate.

You need to adjust both switch contacts with a bit of a gap on the left slingshot.

Pretty sure if you test the Q43 on the MPU, it would measure as a short between 2 of the legs.

The correct way to adjust that leaf switch is bend the leaf close to the stack of the switch under the playfield. It is possible that the 2 leafs are touching under the surface of the playfield, where you have to look down into the hole the switch is sticking out of. Remember the slingshot has 2 switches and it can be either one.

I normally just do an ohm test. Outer leg to outer leg, then middle leg to an outer leg and middle leg to other outer leg. You can compare to another one next to it but I would imagine you would find one of those three measurements reading under 10 ohms. A transistor can short in any of these combinations, so measuring to ground will not always find that the part is shorted.

You can use the tab on the top of the part as that is connected to the middle pin anyway.

For the outer pins you might be able to see from the top side of the board what connects to each of the outer 2 pins. That may be easier to measure.

I usually.pull the board out anyway and measure on the backside of board since it is highly likely to be a transistor problem.

If you swap the leads around on the 2N4401, you would likely get the .4 to .6v reading. Though, long as you didn't see a short and all of them measured the same, then they all sounds good.

You used the diode test. I was suggesting just to use the regular ohm test on the meter (horseshoe) to look for a short between a pair of legs, which you did find. Either way of testing works anyway.

Since the Q43 is shorted, it will not allow the flashers to work. So once you change the Q43, I am expecting all to be good.