Greg was the original weldment that damaged? It's probably coil strength with the mantis weldment but if you can swap in the old one temporarily to see that would work. (Or remove windings, how much I don't know? 10-15 turns at a time?)

Unsolder one of the tiny wires coming off the lug to the coil, unwind it how ever many turns you want. Resolder.

You might have to remove the wrapper to see which wire to unwind. There is a start and a finish to the wire.

LTG : )

Had the same problem when I had a TOM. One of the coil wires is broken. If you can't find it or are disinclined to repair it, then replace.

In the solenoid test, I think it always just pops up for a split second, so don't be deceived by that.

I am having the same problem with my new Mantis weldment. I removed the spring as noted above but this did not solve my problem. I've metered the coil, checked the wire, etc. Did anyone solve this by using a stronger coil, and if so, which one specifically? Thanks.

Bottom. Thanks. If no one responds with a coil recommendation I'll try 11753, this was used for the MM trolls.

Funhouse was having the same issue and it was the spring

I had the same problem after installing my Mantis trap door assembly. I resolved the problem by bending the bottom tab up just a little bit. It was bent up just enough to allow the trap door to touch the playfield. I discussed this problem with Kerry at Mantis and was told this problem only affects a small percentage of those sold.

Hah! Not a problem unless you're in that small percentage...

Yeah, it's like the old Starfish story...

Hey NJ...going to Bask Bar tonight?

putting in a stronger coil, 11753, solved the problem. Also, with the stronger coil you do not need to remove the spring.

Man this shit burns me up. Bought the mantis weldment from Marco https://www.marcospecialties.com/pinball-parts/04-10015.2 and just spent half my Sunday trying to get my trap door to open. When I finally came across this thread and changed the coil it started to work. Weird that the stainless steel somehow causes the coil to be weaker. Would be nice of Marco mentioned something about it in their item description !@#$%^&. I did get it to work using the 11753 coil but it worked better with a 11630.

The problem is stainless steel is non-magnetic. So it doesn't help the coil. Putting steel near a magnet boosts the magnetic field slightly. I could make them out of zinc plated steel but that defeats the purpose of making a stronger, better, not prone to rust or breakage unit. I feel your frustration though. I was frustrated trying to figure it out originally as well.

Kerry - Mantis

Hi Kerry, I just edited some of the frustration out of my post, I apologize but I was all heated up when I posted that. I do appreciate and use many of the Stainless repro pieces you make and think you make great stuff and are an asset to the parts business, I just think in cases like this that whoever sells these has an obligation to disclose these kinds of possible issues. Thanks for explaining...

Just replaced my Theatre of Magic trap door mechanism. I too bought the mech from Mantis Amusements. Replaced the mech and all coil sleeves as well. Turned the game on and the trap door wouldn’t go up more than 1/4” above the playfield.
I bent the trap door forward just a little just to be sure it was hitting the playfield. After doing that it pop up most of the way but it wouldn’t stay up. I read in here about the trap door working after ppl have removed the lower spring. I don’t understand it but it works. Just wanted to add my experience to responses. Thanks for everyones input. Pinside for the win again.