Could be this, straight from the DE repair guide: http://techniek.flipperwinkel.nl/desega/index1.htm

Wrong PPB Relay installed on some TftC Games.
During production of Tales from the Crypt, the wrong PPB L/R select relay at K-1 was installed. This can cause solenoids to activate randomly, and flash lamps to not activate at all. The problem was the PPB's K-1 relay was installed with a 24 volt AC relay, instead of a 24 volt DC relay. The incorrect AC relay had a relay coil winding of about 2 ohms, where the correct DC version was about 650 ohms! The lack of ohms will cause the relay to burn and fail. The relay can be identified easily because it is labeled "24v AC", where the correct relay is labeled "24v DC", or the relay's winding can be measured with a DMM. Games with serial number 101664 or later have been inspected for this problem. If a 24 volt AC relay is discovered, replace it with the correct 24 volt DC relay.

You should not be blowing this many transistors this quick. There is something very wrong with your power. Check that relay.

Does the game turn on? Are a bunch of coils locked on? Do you still have hot components? what is the symptom you are trying to fix?

Hot generally means shorted on the transistors.

Without looking at the manual, are you also checking the pre-drivers for those transistors that you are changing out? Maybe they are also bad and are causing the TIP ones to heat up and fail.

Getting ready to start on my own gremlins with a TFTC.

Good Luck.

What was the resistance of the coils in question when you tested them? When you say "shooter coil", you meant shooter lane coil correct?

From the repair guides:

"When Replacing Bad Driver Transistors... (a repeat warning!)
ALWAYS check the coil mounted diode too! Often the coil mounted diode will break, causing the driving transitor to fail. If the diode is not replaced also, the driving transistor will fail again and again. This is often overlooked in DataEast/Sega games." (make sure it is there, correctly oriented - before proceeding)

>Q2/Q8, Q3/Q9, Q4/Q10, Q5/Q11: special coil (switched solenoid) drivers. Connects to chip 12A (7402). On CPU revision 1 or 2, the logic ends there. On CPU revision 3, chip 12A (7402) connects to chip 11C (7407), and then to PIA 8H or 9B or 11D (6821). On all revisions, resistor network RA24 (4.7k x 8), capacitors C40-C45 (.1 mfd), and diodes D1-D6 (1N5234) are used and can fail (causing the affected coil to lock on).

>On games Back to the Future and later, there is a potential problem with this backwards compatibility. The reflexive circuitry can be damaged, and cause the special coils to lock on. This can be very frustrating. For example, say a pop bumper coil locks on immediately when the game is powered on. After replacing its associated TIP122 transistor and the 2N4401 pre-driver transistor, and checking the coil's diode, the coil is still locked on! So go back a step further, and replace the 7402 chip at location 12A or 12B. And still the coil is locked on. Finally go all the way back, and replace the 6821 PIA chip at location 8H or 9B. Yet still the coil is locked on!

The problem could be in the parallel, but unused, reflexive circuit! If just one of the small capacitors at locations C40 to C45 (.1 mfd) shorts, its associated coil can lock on. This is a very common, but confusing problem. Also, one of the diodes at locations D1 to D6 (1N5234), or the resistor pack at R24 (4.7k xcan short (less likely, but still worth checking). In CPU Revision 3 games, these components are unused, but they can still become damaged!

It is easy to determine which circuit a game is using. If connector CN18 (upper right hand corner as facing the CPU board) has a plug connector attached, the game is using the older "reflexive" special coil circuit. No connector at location CN18 means the game is a CPU Revision 3 or later machine.

I know you are ignoring my coil question but let's move past that point. I am still willing to help you. When you test a predriver OR a main tip102 transistor, they quite often test good, but are in fact bad. If you can't figure out this problem, I would replace all the pre-drive transistors and main drive transistors in the questionable circuits, even if they are testing as good. Shooter lane, drop targets, as well as the others (scoop, ect, ect). Transistors are cheap and you should be replacing all pre-drivers in any circuit that had any component(s) fail as a steadfast rule.

I can tell you that I have personally found over 100 transistors that tested good but were toast. I saved some if you want to see a few for reference/testing purposes.

You know, if you don't fix this thing, you are going to have to put it up for sale with the statement "It's probably just a fuse"

(now ducking from flying tea cups)

This won't help with your short, but my drop target mech is also missing one of the clips on the small shaft. After replacing a drop target, I'm guessing the tech left it off so it would be easier to replace the next broken drop target (which it is). What he did to keep the small shaft from sliding was to wrap a zip tie around the shaft on the end with the missing clip and looped it around the drop target frame, pulling it tight . This does keep the small shaft from moving--so far I don't see any down side to this mod. It sure is easier to cut the zip tie than to try and remove and replace that tiny clip.

At this point it looks to be an IC at fault that controls multiple things...

Some more things to look at...

Whenever multiple things are going wacky in a pin, the similar IC controlling those things will likely be the blame.

In your case it would likely be the 7407ic chip directly to the left of the "Special Ciol Drive" section of the MPU in the schematic section of the TFTC manual available on ipdb.org. Or, it could also be a shorted closed resistor in that same circuit...

also...
THIS thread:

https://pinside.com/pinball/forum/topic/tftc-3-solenoids-not-firing

suggests your problem could be a faulty plug connection. Very high resistance could build up heat when a coil is fired and blow a fuse or other components causing your symptoms.

This is a very "generalized" view of how I would approach it, breaking the system down and systematically testing and repairing everything.

Read first: http://techniek.flipperwinkel.nl/desega/index1.htm and refer to it often.

Disconnect everything from every board, disconnect every wiring harness except input power to the power supply board. Thoroughly test power supply board and fuses.
Reconnect input power harnesses to CPU board.
Reinstall displays, test displays
Test CPU board switch interpretation. Reconnect playfield switch lines to CPU board and verify interpretation.
Test solenoid outputs, then reconnect solenoid outputs one at a time, each time testing for proper operation.
Reinstall lamp matrix, test lamp matrix.
Reinstall sound system, test sound system

Just for kicks have you tried a different power supply? You stated you first swapped out the power supply upon your first failure and have had trouble ever since. It's probably unlikely but maybe the power supply is not working correctly under load.

1. Swap in a different known good power supply in there
2. I would replace the transistors and mini transistors in question
3. Cut the power wires to the coils that are associated with the blown out transistors.
4. Test coil ohms with wires cut, and diodes on the coils
5. Power up the game with those solenoids removed and see if anything blows.
6. Hopefully everything is still ok at this point, and then reconnect one solenoid coil at a time and power up after each one and test.

Check the transistor for that coil before installing the new one. I think you are on the right track.

Does the transistor test bad after the coil locks on? You HAVE to have a short in that circuit. For fun (not really fun), remove the connector for that coil off the driver board. Then do a test wire for just that coil to see if it works ok. I'm fairly sure you have somebad wiring either on the connector, the pins on the driver, possibly a jumped solder pad at the transistor for that coil.

Side note, possibly easier. Have you swapped in a different main board and or PPB board that is known good? At least then you can chase it backwards from there. Hopefully it tests fine with different boards. If not then that tells me it's a wiring issue / short.

Also have you retested the voltages at the coil and at all the test points? Could you have an over voltage situation?

Any acid damage to your main board? So sorry to hear you are having so much trouble with it.

Glad I was correct with the jumped solder pad on the driver Congrats on the fix.

Allen and Eric both great guys and repair techs.

Right on power up the coil locks on, or after it boots?

Blown transistor, easy fix.

What he said. Check the Pre-Driver as well. They often go in a pair.

You probably had a weak power supply, got some sort of voltage spike and that took it out. Most likely same cause of all the problems you had earlier. Replacing the power supply should help.

A blown transistor isn't necessarily indicative of a bad PSU. It could be a lot of things. They burn up for lots of fun reasons. Anything that'll cause a coil to lock up will do it. Those PSUs are fairly robust, and if it was rebuilt recently with new caps and all, it should be fine still.

Awesome!