(Topic ID: 297726)

Williams Match Stepper Unit

By megoman

83 days ago

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  • 18 posts
  • 4 Pinsiders participating
  • Latest reply 73 days ago by megoman
  • Topic is favorited by 2 Pinsiders


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#1 83 days ago

I’m having an issue with a Williams match stepper unit. I’m sure there are others that had the same issue and can share how they fixed.

The stepper unit itself works and has all of its parts + springs. The issue I’m having is that the nylon lever that moves back and forth when the metal plate is pulled by the coil is collapsing behind the nylon gear. The lever moves correctly a few times and then collapses and gets stuck behind the nylon gear.

If I move the metal plate manually I CANNOT recreate getting the nylon lever stuck behind the nylon gear.

I’ve attached a few pics showing the unit and what is happening.

Many thanks in advance for the feedback.

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#2 82 days ago

the coil yanks the armature plate a lot harder/faster than you can, so if pieces are worn you may have your problem.

the one thing you can do something about is the position of the brass finger that prevents the shaft from turning backwards when the pawl is pulled back (pawl = the plastic pusher you are having trouble with).

make sure the finger has good tension against the ratchet and is positioned to hold the ratchet so it can't spin the wrong way. Loosen the screws to slide the finger to position desired.

look for other adjustments to the armature plate position ... the goal is the pawl retracts enough to reliably grab the next ratchet tooth, but not further.

if your problem happens often enough, mark one of the big alternator teeth with a sharpie and watch as you hit whatever playfield thing makes the unit step. You want to see if the shaft turns backwards or the pawl is slipping off the edge of a worn ratchet tooth.

part numbers are for a 10 step unit are:
3A-7366 - pawl
A-7595 - shaft with alternator

12 step unit:
3A-7369 - pawl
A-7567 - shaft with alternator

I don't remember if the coil screw has a brass washer on it, but if it does make sure it's between the coil and the frame (not under the head of the screw). If it needs a washer and it's not where it should be, that'll make the armature plate pull the pawl back further.

what game is it on?

#3 82 days ago

Many thanks for the detailed feedback regarding the unit.

I checked the brass finger position and it is properly placed (ratchet cannot spin backwards).

My plate is pulling too far back when the coil fires and this is dislodging the pawl.

There seems to be just one point of adjustment
that can impact the plate - namely the metal plate at the bottom the holds the spring (photo below). My plate is positioned such that the bottom spring is at its loosest tension.

I moved that bottom plate to a few different positions (all resulted in the spring getting tighter) and each time I was able to manually displace the pawl. No good so I put back to original position.

With no other way I can see to limit the back and forth movement of the pawl, I took some electric tape, cut into pieces 1/2” wide, layered several tape pieces and put at the very top of the copper plate from the coil. Tested out how many pieces of tape could be added so that mechanism still worked manually and that is where I netted out.

Not the ideal solution, but it worked and stopped the pawl from getting displaced.

Would ultimately like to fix without the use of tape. Other thoughts / suggestions welcome.

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#4 82 days ago
Quoted from megoman:

My plate is pulling too far back when the coil fires and this is dislodging the pawl.

Does the coil in the unit match the coil specified on the schematic? It may have been replaced at some point with a slightly shorter coil.

Could the pawl be worn so that it's a little shorter than it should be?

Should there be, or could you add a spacer or washer between the coil base and the frame to push it a little closer to the armature?


#5 82 days ago

mark's suggestion of a spacer washer between the coil and frame would be more reliable than the tape.

the pacific pinball museum has a prospector in the warehouse ... no paperwork tho. I can pull it out monday and take pics of the unit in that game for comparison.

#6 82 days ago

Thanks for the feedback.

I missed the part about the coil + washer from first post. Sorry.

Great point Mark made about the coil and does it match the original spec. This unit is on a Prospector game and it has a Sega coil with what looks to be original solder joints to the game wires.

I’d like to think the Sega folks mimicked the original Williams spec for the coil, but maybe not?

As for the washer, there are two on the outside of the coil. A large brass one and a small silver one. Don’t know if that is the correct configuration? Really appreciate you taking a look at the game at the Museum. Curious to know what coil is in the game and how washers are configured.

Should my current setup prove to be correct, I will try to add a thin washer between coil base and frame as agree that is a better solution than electric tape.

You two guys are the best (M & D)!

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#7 82 days ago

Meant to also say there does not appear to be any wear to the tip of the pawl.

#8 82 days ago

typically a brass washer goes between the coil and the frame. It's there to mess with the magnetic field and help prevent magnetizing the frame.

however, I can count on one elbow the number of segasa games I've worked on in the past year, so don't know how they mounted coils. You can look at other relays in the game to compare.

#9 81 days ago

I’ll look around the machine for similar type coils for possible comparison.

The brass washer on the outside is rather thick and I think much too wide to be located inside the frame and still have plate function correctly.

#10 81 days ago

Sadly the parts catalog doesn't specify where the washers go:
Segasa_Sonic_PartsCatalog_pg_9 (resized).jpg

#11 81 days ago

Amazing you even found this

#12 81 days ago

I took another look at where the back of the coil is relative to the back of the frame. There is a narrow gap (back of coil is NOT touching back of frame - see photo) and a washer creating that space.

If I’m going to add another thin washer, does it need to be a particular metal (copper, brass) or will any washer do?

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#13 81 days ago

As baldtwit pointed out the brass usually goes inside the frame. I wonder if the thin washer inside and the brass washer outside were swapped at some point?

I just noticed these that might be helpful if swapping the washer doesn't work:
Brass Screw w/ Brass Washer 8-32 on http://www.pinrestore.com/Hardware.html

#14 81 days ago

Here’s a similar coil inside the cabinet that has the same brass washer on the outside.

There are 12 of these types of coils I. The cabinet and they all appear similar.

Looks like the addition of a thin brass washer will be the permanent fix.

Thanks again for the knowledge about this type of stepper plus your input + help

#15 79 days ago

if you use a steel/aluminum washer, put the brass washer next to the coil.

below are pics of the museum game.

I can't force the pawl down like yours is doing, so hopefully the pics help you find the issue.

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#16 79 days ago

In post 3, first pic -- should the spring be pulling the plate all the way? It looks 'away'. Could the over pull be a factor of fatigued spring? << asked by he guy who never has a clue!! Have a Space Mission with the same match unit and getting the spring tension just right was one of the issues.

#17 78 days ago

Many thanks for the pics from the museum game.

Question - an order was listed for use of a steel / aluminum washer. Will there be a difference in how the unit functions based on the type of washer used (brass vs steel / aluminum)? If brass is better/preferred, then I’ll use brass.

Zaphod - thanks for the input. When my plate is pulled by the coil it goes so far back it’s pulling the pawl with it (too far back causing pawl to disengage). At issue is the total amount of space available for the pawl to travel. A tighter spring would provide more tension for the return, but the plate will still move the full distance and touch the brass end when the coil fires.

Welcome other suggestions on what may be causing the issue on my step unit.

#18 73 days ago

And to final close the loop I’ve included photos of the tip and length of pawl.

Looks similar to the photos that Baldtwit sent.

Thanks again to all for the help

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