Could you provide images of the circuit boards in the head?

I'm just curious if there is "battery damage" https://pinwiki.com/wiki/index.php?title=Bally/Stern#The_Single_Largest_Culprit_in_MPU_death

also if you have original or replacement boards

There are some troubleshooting steps to isolate where that short may be coming from if not from battery corrosion ( I don't have them at the top of MY head but other Pinside members do )

I think you're talking about fuse F4. That's 43 volts DC for the solenoids. you may have a stuck on solenoid or a short in the solenoid wiring.
Remove connector J1. If the the short goes away look for a problem on the playfield.

The boards visually look good , battery had been removed from MPU with "NVRAM" installed

New capacitors on SDB and some voltage regulator upgrade seems to have been done

In the pic of the playfield I noticed 2 balls locked in the "ball-walker" (or ladder) area. Upon start up that is one of the first solenoids to fire (along with the coin reject solenoid on the coin door)

With power off,First visually inspect those 2 to see if they are burned , you should be able to manually actuate the "ball walker" solenoid to release the balls

If you have a multi-meter it's be best to test for a resistance on those coils. you can manually actuate all the others as well.

F3 is the +12v fuse that the +5v is derived from. Pull the 25 pin connector on the right side of the solenoid driver board, replace the fuse, turn the power on and see if it blows. If it does, you have a fault in your rectifier board. If it doesn't, you have to move on to the other boards, the normal sequence is to disconnect all the boards, and with only J3 and J2 connected to the rectifier board, turn on the game, test all the voltages on the rectifier board. If good, move on to connecting up only the solenoid driver board (which is also part of the power supply, generating the regulated voltages). Test there. If good, add the mpu board. Then the lamp driver board. Then the sound boards.

Looks like Larry Ricky did a lot of work on the boards in that game. Interestingly it's a Bally-35 mpu board there with the Weebly update to make it act like an mpu200, but I doubt that's related.

Might want to check that the clock circuitry has been updated to MPU-200 spec.

nice catch by oldschoolbob

The rectifier board image does show fuse "F4" being blown , the confusion is the "e3 test point"

On the SDB it's tough to see if the components surrounding "q13" are ok , also on the schematics it's tough to distinguish the difference between the associated "Ball launcher" and the "ball kicker"

There are times if either the coil or a board component fails that drives the coil it takes them both out.

It's great to have both slochar & Quench on this thread & their diagnostics by removing connectors will help quickly resolve the culprit.

Stern F2k - q13 (resized).jpg

Stern F2k ball launcher - kicker (resized).jpg