POTC ship mechanism problem - Solved

[Michi]

Hi guys, looking for inspiration on a problem with my POTC ship mechanism.

 

Basically, the ship will come up, but it won't go down. The sails are working fine, no problems.

 

When I play and sink the ship, the ship won't go down into the playfield. I hear a lot of whirring from the ship motor, but the ship won't move; sometimes it shudders a bit. I have to power the game off to get the ship motor to stop.

 

If I push the ship down into the playfield by hand and turn on the game, it comes up just fine, no problems.

 

When I run the ship test, the same thing happens. The ship won't go down, ship motor making lots of noises until I power the game down.

 

I did some searches, and it looks like the most likely causes are either a worn clutch, or a worn gear box, but I'm not sure how to decide which (and buying them just in case is a tad expensive). If anyone has any tips, I'd be much obliged!

 

Cheers,

 

Michi.

Edited September 13, 2016 by Michi

[Amigas]

Hi Michi

Yes this has happened to me as well, the ship comes out from the top with the sails removed ,there is a nylon slide guide item 8 and bronze pivot bushing item 3 which is very loose on mine can't find a replacement as not listed on the parts list .What happens is the bushing wears in the main supporting plate (so the hole the bushing goes through wears) .I Just dismantled the whole thing and applied small amounts of teflon grease to the slide assy and re lubricate the bushing, think the motor assy is fitted with a clutch so if it binds or a piece of say playfield plastic gets caught it won't burn the motor out

See link http://www.sternpinballparts.eu/index.php?item=&action=page&group_id=20000151&lang=EN

AMIGAS

[Michi]

Hi Amigas,

 

thanks for the tip! I'll pull the ship out tonight and see what I can learn. It looks like the bushing is part of the ship support (part #515-7573-00). It's available here (but not cheap): http://www.marcospecialties.com/pinball-parts/515-7573-00

 

From the photo, it seems the bushing comes with that part.

 

I'll see what state mine is in tonight. The other likely culprit seems to be the clutch. There is a thread on pinside about this here:

 

https://pinside.com/pinball/forum/topic/potc-ship-problem

 

It mentions three "leaves" in the clutch that can be swapped around. I don't know what is meant by that. Does the round clutch actually come apart?

 

This is the clutch I'm talking about: http://www.marcospecialties.com/pinball-parts/545-6182-00

 

Cheers,

 

Michi.

 

- - - Updated - - -

 

Ah, looking around more, the clutch plates are visible on page 80 of the POTC manual. Looks like there are three clutch plates (part #535-9811-04) behind the backup plate inside the plastic clutch part. Anything slipping here would explain why the motor keeps turning, but the ship not moving.

 

Might also be necessary to thoroughly clean the entire mechanism. I'll see what I learn when I pull the thing apart.

 

Cheers,

 

Michi.

[JOKERPOKER]

Hi @Michi,

 

As Amigas said it is a good idea that you pull it out and give it a good clean.

Lower the ship and it's only a matter of 6 wood screws and a couple of connectors and the WHOLE assembly will come out through the bottom of the playfield. This will make it much easier to work on.

 

My first one used to do this and would wail around and hit the sneeze guard and cause havoc. I cleaned and lube (DRY LUBE and SPARINGLY) it and it did improve it by 90% it would still glitch sometimes but i would just reset it in the test and it would be fine again.

I had no such issues with the following 2 POTC that i have owned.Check that the home switch (lower) is working correctly and not slightly bent as this was also part of my problem with the first one.

 

Your issue may be with the home switch in the (raised) position. As it won't sink i would be checking that out as well.

[Michi]

Hi Scott, thanks heaps for the pointers, I appreciate it! I'll check the ship up/down switches while I'm at it. I don't think the ship won't sink because of the switch though because the motor clearly is trying to move it (I can hear the motor going). It's just that the ship won't physically move.

 

Right now, my money is on the clutch, and possibly friction being too high in general, so the clutch lets go to protect the motor.

 

Any particular brand and source of dry lube you can recommend? I have a can of teflon spray dry lube kicking around, but I'm not sure whether that's the right thing to use. And I've heard plenty of warnings regarding lubricants in pinball machines. Apparently, the lube tends to accumulate dust and gunk up, and make matters worse in the long run, and I don't want to use something that will cause trouble later.

 

Cheers,

 

Michi.

[JOKERPOKER]

A teflon spray would be ok just make sure you don't get it anywhere you don't need it.

Dry graphite is good as it doesn't allow build up. In home use it's not as critical as when out onsite just use it sparingly and wipe off any excess

[Michi]

So, I pulled out the ship and had a good look. Nothing obviously wrong.

 

Removed the motor housing and the clutch. Removed the clutch plates and found that the plate facing the shaft had some minor wear marks (nothing serious), but swapped the second and third plate anyway, so a clean unmarred surface would contact the drive shaft.

 

Found some gunk around the bronze bushing that looked suspiciously like gummed-up lubricant. Removed as much as possible with alcohol and applied a tiny amount of PTFE spray dry lube. A very small amount of play in the bushing, but nothing serious.

 

Cleaned the nylon track and generally inspected the mechanism for any obvious defects. All good. Ship moves very freely and easily with the motor removed. No stickiness or anything like it.

 

Re-assembled the entire thing and tested it with a 9V battery. Ship motor moves the ship up and down just fine. (Slowly, seeing it's only 9V, but working fine.)

 

Used multimeter to test the bottom switch with the ship in the bottom and half-raised position. Switch works, and diode across the switch is fine too.

 

Put the whole thing into the machine and tried. No joy. Exact same symptoms as before. Ship doesn't move or, occasionally, moves down a little bit and then snaps back into the up-position. All the while the motor is whirring and won't stop until I turn off the machine.

 

I can easily move the ship while it's in the machine. (It takes a bit more force because you have to turn the motor through the gear box.) But moving it up and down works fine, and there is no obvious mechanical obstruction.

 

Ran out of time to do more. Next candidate is the top switch, which is mounted on the playfield. Hopefully, I'll find something there. If not, I'm fresh out of ideas.

 

Does anyone know how the ship logic actually works? Obviously, the top switch is there to turn off the motor when the ship hits the top position, and the bottom switch is there to turn off the motor when the ship reaches the bottom position. Assuming a fault in the top switch, would that cause the ship to fail to move? (But mine *does* move or, rather, the motor comes on and then the ship doesn't move. When it does move, it moves down a little and then snaps back...) Strangely, if I manually push the ship down and then turn on the power, the ship moves up perfectly and stops exactly where it should.

So, the problem is only with moving down, not moving up.

 

Weird…

 

And wonderful. If it were easy, it wouldn't be fun :D

 

Michi.

[JOKERPOKER]

Hi Mitch,

 

Do a test with ship in the uppermost position. Do the sails drop first before the ship tries to sink. If that solenoid is not working properly these is a switch there somewhere that would stop it sinking so as not to damage the sails from memory (could be wrong memory not as good as it used to be?)

 

I know if the sails get out of sequence that will cause problems like my first one.

[Michi]

Found it.

 

I couldn't figure out why the ship was working fine when I powered it with a battery, but not when in the machine. Almost as if there was a mechanical obstruction, because the motor was whirring, clearly trying to move the ship down, but failing to move it.

 

So, I figured I'd try to help the ship along when it was trying to go down, to see whether I could spot something. When I did that, I found that when I was pushing the ship down, the motor was pushing back against me. In other words, telling the machine to make the ship go down actually made it try and go up. That doesn't work when it's up already :)

 

The ship motor is controlled via a relay on a board underneath the playfield. The relay reverses polarity when powered on. In the resting state, the relay makes the ship go up; with the coil powered, it makes the ship go down. Measuring at the coil showed that the coil wasn't powered. Measuring on the driver board showed that the transistor was switching correctly. That didn't leave anything else but the wiring. Sure enough, broken wire at pin 3 of J6, which goes to the relay. (I have a Y-connector there for an LED backboard that has a few flash lamps in addition to GI, and it was that short piece of wire from the connector that plugs into the board, to the connector that the original J6 connector piggy-backs onto.

 

So, all is well, thanks for all the suggestions. I learned something about systematic fault finding in this exercise, and my ship is all clean and moving very nicely now because of it all :-)

 

Michi.

Edited September 13, 2016 by Michi
typo