The main 5A SB (replaced the 15A FB as recommended) is blowing and taking out some of the solenoid fuses on the fuse board as well. Presuming it's the bridge rectifier C3 here giving too much juice?

It wasn't blowing out the 15A FB but it would blow out ALL the solenoid fuses on the fuse board; now with the 5A SB main it's just taking out a couple of the fuse board 2A SB before giving way.

So, bridge rectifier C3 most likely culprit as if it were some of the transistors on the main board for the solenoids, it wouldn't get all the way back to the 5A SB main - it would just take out the corresponding fuses on the fuse board, correct?

TIA!

Hmm. . . sometimes when powering on, the 5V is about 8.8v. Other times, several solenoids lock up. Then, other times, the voltage is about 4.8 and everything operates normally, save for the aforementioned solenoid issues.

I've replaced several of the 6044 transistors and have brought some of the solenoids back from the dead but changing some of the 6044s has no effect. Having a hard time finding the chip that controls the switches for the solenoids on the schems. Wondering if it's not a chip issue on the remaining bad solenoids.

More concerning is the varying voltages upon power on. Any advice there - really want to avoid anything but 5v on startup, of course.

TIA

No. Only area that is hot is the large ceramic resistor near the 5v regulator, near the solenoid section.

Ah! Started focusing on the voltage regulator on the main PCB and noticed it didn't have any nuts on the end of the screws. Surely, they should be there. Checked pic online - yup. Nuts missing. Nuts installed. Consistent 4.88v every time turning it on now without fail!

Now, back to the solenoid issues. . .

Only ones that are still dead are 1 (outhole), 3 (upper drops), 6 (lower drops). Upper drops, when power is applied, stays engaged constantly (disconnected power for now). Lower drops and outhole seem to get no power.

Lower drops was just the 6044 transistor - all good now. Outhole and upper drops next.

While troubleshooting the outhole solenoid issue, mistakes were made:

https://pinside.com/pinball/forum/topic/middle-earth-dead-switches#post-3870963

EDIT: Switches fixed.

Upper drop target solenoid was remaining on all the time. Transistor and diode replaced - no change. 9334 at C14 changed out (74LS259 subbed in) and that took care of it.

Outhole - would rapidly stutter and blow out the fuse. Replaced transistor and diode as well as the 9334 at C13 - now just blows out fuse after kicking weakly once. Will update when fixed. Suspecting diode on coil or coil itself.

Outhole kicker was the coil itself.

100% working now!