Hi folks,

Simple question.

What causes a coil to lock?

On Thursday, my very happy Haunted House table was playing fine. Turned it on Friday night and... "Thunk! Thunk! Thunk! Thunk! Thunk!"

I grabbed my DMM and opened the sucker up. One of the coils went from 2.8-ohms resistance to suddenly 15.8-ohms! Wow.

Ordered a new coil from Marco (actually, a couple of coils just in case) and will replace it when it arrives.

But, I'm just wondering... why do coils lock? Old age? Faulty wiring? Comets? Voodoo priests? Sun spots?

And, yes, ALL of the necessary/mandatory System-80 ground mods were performed a long time ago.

This is just a general question.

Thank ye.

-Bob

locked-coil.jpg

This is definitely a nice start. Thanks a bunch so far!

The coil is for the hole-kicker on the lower-playfield.

I have the schematics, including part numbers, along with a bunch of other System-80 guides and haven't come across a bulletin on this particular coil.

Oh, the driver board is a new Ni-Wumpf board. I'll check that out too just to be sure that isn't acting goofy.

And the fun begins.

Actually, I hadn't turned the game on at all when I took that picture. I mean, it had been plugged in but not turned on. The table had been turned off all night.

Verrrrrrry interesting.

Something simple like a short?

I'll remove the lower playfield and inspect the connections if that's the case.

Okay, new approach here folks.

It appears the coil is fine. I tested the resistance of an equal coil on the main playfield and it shows the same value of 15.8-ohms. I guess it's probably a short or something.

Thanks Crash, I thought all of the coils had the same resistance value. I guess not.

Trying another approach. Maybe tomorrow.

Right. Update:

Everything's fine. The coil's working and was never faulty.

I removed the lower playfield, checked everything out, made sure there weren't any wires touching and re-installed the playfield.

Turned the machine back on and.... no thunks. It's just fine.

I examined the switch to make sure it had the proper clearance. I think that must have been it. Just needed a little jostling to free everything up.

Thanks for the advice everyone. I'm still *very* new to pinball maintenance, mechanics, and electrical engineering overall, so most of the time I really have no idea what I'm talking about.

I guess I know *just* enough to be dangerous and make people think I'm smart. Hah.

So, yeah. Thanks everyone for the pointers.

Maybe next time I'll do some research before immediately going to you guys.