https://sites.google.com/site/pinballfaz/

Faz is the man!

I would start with the bi directional board. There is a capacitor on there that likes to leak, and take out the trace below it.

I'm unclear if your motor is working at all. It sounds like you pulled the MPF... pull out the motor/gearbox then pull the motor off the assembly.
Plug the motor in the connector to check the motor. I really doubt the motor is burned out; it really does not get that kind of abuse.

faz

Assuming "stuffed"=="not awesome"... and yea, probably is.

I'd be happy to do a Facetime/Tango chat if you want to talk through it?
faz

EDIT: Isn't it 3:00am in AUS?

I wish to bump this and say that if you hear some gear noises but the axle doesn't turn means your gear box most definitely is "stuffed." I had mine go out, and it's pretty obvious. It goes up and then just doesn't, yet the motor is spinning and (some) of the gears are turning, yet the axle on the opposite side isn't spinning... it's doomed.

Pinball Resource may have one or rebuild for you.

I've done that too, but it doesnt always indicate an issue. You're gear box can be going out and yet will still pass this test.

Keep in mind that the game powers that motor with 11V more than the 9 volt battery, so if there is a problem with the gears, it should be exposed by this. Many people seem to disassemble the gearbox to “fix” a problem that isn’t even there. In my case, the motor wasn’t being given enough power while in the game because I had lost one of the -2- wires which are feeding the motor

If you lost one of the two wires, you won't just get weak power, you get NO power.

Not 1 wire to the motor, there is a flasher (I think it’s the doctor 5 flasher) that the mini play field power also runs through - in my case, there was a connector that had 1 hot wire from the harness and 1 hot wire from that flasher which joined in the connector. The connector (if I am remembering correctly) is a 2-pin molex which then connects to the motor

There is only one set of wires feeding the motor power. The flasher can be totally disconnected and not harm the performance of the playfield.

yup... it's a DC motor. This is the one time where in "sci-fi" terms... "Reversing The Polarity" actually does something. -12V or +12V causes the MPF to move CW or CCW.

faz

I wonder if mine was wired incorrectly? That is pretty bizarre

Whoops... sorry.. I misstated something. The voltage is +/- 20V. and I'm not illustrating which voltage drives CW/CCW.. I don't remember. The important thing is that it's just a simple DC motor.

faz

pinball_faz

I am in a similar quandary. Recently purchased a Doctor Who and the MPF has been rock solid for a month. Two days ago it froze in the up position. On inspection, it appeared that the positive power supply wire to the motor popped its connection.

Upon reconnection, it worked fine for about a game and then MPF started slipping.

I popped the playfield up - and was able to move the MPF along its track with very little effort.

Here is a video -

Before I go out and drop the $, I just was hoping for some independent confirmation that the gear box is hosed - and my best course of action is ordering a new motor/gearbox and replacing that.

Thanks for any guidance. This is my first machine and I am excited to learn with this community.

Thanks,

Morbius

IMO... something indeed is "hosed". But before you put a new gearbox/motor in you need to check a few things.

I hear the motor spinning really fast and the gear box jerking along. That's a combination that does not happen.

If the gear box is good and you stop the motion, the gears will break under all circumstances. It's direct drive, there's nowhere for the energy to go.
If the gear box is broken, why does it keep moving?

Check the path of the MPF completely on all four sides. Make sure it's 100% free of any binding/rubbing.

Use my white paper to tear down the whole thing and build it back again. Just the physical parts (leave the top of the MPF alone).

When the brackets are out, you need to run them with the motor alone up/down to make sure the action is smooth. If they got hung up, they warp/twist. You may need to reshape slightly.

I'm wondering if the set screw on the cam is loose or slipping. This would be a simple fix if that's the case.
Another possibility is one of the gears inside the gearbox has sheered off it's mount. There's some delicate repairs to repair the gear collet but unless it's done correctly it could turn into a lot of wasted time/frustration. But if you love to try to fix things, this would be a good one

Let me know. Glad to call you too.
faz

Inside the box there is a brass sprocket pressed on a steel axle wich can be welded,
it fixed my problems ...

Thanks, pinball_faz

I am going to take the MPF out tomorrow morning and follow your diagnostic suggestions on Sunday morning. Thanks for the offer on the call! I may take you up on that.

pinball_faz

It took me some time but I finally had some time to separate the motor from the assembly - and the same behavior is going on without being attached to the Cam.

See video -

It feels like a few of the teeth are grabbing on the screw, but generally it just slides or binds up.

Am I better off just buying an new gearbox and motor assembly at this point or is it worth while to attempt a fix?

If worth a fix, any idea how I break into that gearbox?

Thanks!

Normally the case is held together with four rivets.

Looks like there's some torx screws. Assume there's a nut on the other side. Get a torx bit and open it up. Peek around but I see a new gearbox in your future. My guess is someone's already been inside hence the non-standard fastener.

I'm betting someone got medievil on the inside with a pair of pliers and blowtorch.

Should just unscrew nice and easy. Take some pics... and don't forget to share
faz

pinball_faz

Well, I got the motor gearbox and reassembled and while it wasn’t binding, I noticed a bit of torque at the top and bottom of the cycle (as the cam reaches the top and bottom).

During that, I noticed that the ring and e-clip on one side were missing. Does anyone know the size, part number, and/or designation of these?

Thanks again!

Morbius

F02FC9BC-6AC8-47B7-99FD-B5272AC1ABD1 (resized).jpeg

90AE1630-4BF4-4C99-8411-AAD83AF4FDC2 (resized).jpeg

Just take the entire thing to a good local hardware store. They should have a variety of e clips

Dude... you have one of the e-clips.... take THAT to the hardware store and say... "I need one of these".

easy peasy
faz