Control unit disassembly - by anonymous

The overhaul section on the site talks about taking the control unit apart, but the example machine is Magic Ring - not ideal as the control unit doesn't have the typical search disc out on the end. So this writeup will take apart a control unit for a screen game.

Get the switches out of the way
switch bracket screws
remove three screws ... and maybe bundle clamps

Remove the two screws fastening the switch bracket to the metal shelf plate with a long phillips screwdriver. A magnetic bit holder will make your life easier.

Remove the screw fasting the left end of the switch bracket to the motor bracket. On many games, there's a metal bar here with a plastic cable clamp for the wire bundle. This game is missing that. You can leave the bar/clamp attached to the wire bundle after taking out the motor bracket screw. There may also be a plastic clamp at the lower end of the bundle - if so, unscrew it so it doesn't break.

flip the switch bracket back/down out of the way
switches out of the way
flip the switch bracket away

Flip the switch bracket back and down to get it out of your way.

Remove the slip ring wipers
slip ring wiper bracket screws
remove slip ring wiper bracket screws
slip ring wiper bracket off
leave slip ring bracket hanging

Remove the slip ring wiper bracket screws and leave the slip rings hanging.

Notice some alignments you'll need for reassembly
reflex unit
important alignment

There's two adjustable components - the search wiper locking coil/unit and the search wiper pin switches. The wiper lock coil can be slid on the shelf plate to set the wiper contact "home"/locked position. Often the contacts are between rivets, but it doesn't matter much since the rivets on that area of the search disc aren't connected to anything - except on most late-model 6-card games. For late-model 6-card games, make sure the search wipers are locked in the position shown on the manual diagram.

For most games, all you care about is the search wipers are locked somewhere around position 2 on the search disc, and if there are switch stacks lifted by a pin on either the locking came or the search ratchet cams on the other side of the search disc, the wipers need to be locked so those stacks make sense.

On this game, there's a switch stack that should be lifted by a pin sticking out of the locking cam when the wipers are locked. You need to lock the wipers so the stack is fully lifted by the pin and/or adjust the stack position so it's sitting on the top of the pin.

Remove pin switches
pin switches
remove the two pin switch bracket screws
pin switches
flip bracket out of the way

Make your life easy and take the pin switch assembly off the search disc bracket. You won't have to deal with adjustments when you put it back on, assuming it's ok where it is. Take out the two screws and flip the switch bracket out of the way.

Remove the shaft screw, spring and washers
shaft screw parts
remove shaft screw, spring and washers
pull wipers from back
pull wipers from back. Do NOT pull on hub.

Spin the wipers around to a position that looks like they will clear the search disc brackets without mangling wiper fingers. On some machines, there's no position that works, and you need to:

  1. unscrew one of the search wiper brackets from the shelf plate
  2. remove one of the nuts/bolts connecting the bracket to the contact plate. The top is usually easier to get to.
  3. pivot the bracket away to make more room

With the wipers more-or-less positioned to clear, remove the shaft screw - watch out for the spring tension. Then take off the metal cup washer, bakelite washer and nylon or metal washer.

The search wipers can now be slid out on the shaft, but you may need to do the next step first. Do not pull on the slip ring hub or locking cam, it's only held on by the wires and electrical tape. Pull on the area where the wiper arms meet.

Remove the search wiper locking coil/unit from shelf plate (if present)
search wiper locking coil/unit
remove search wiper locking coil/unit

On games that have a search wiper locking coil, it will probably prevent you from pulling off the wipers. Occasionally a game has no wiper fingers on a couple arms and you can leave the locking coil unit on, but you won't be that lucky.

The reason for taking out the shaft screw first is that it may be easier to get at the mounting screws if you can move the wipers in/out on the shaft. If you can easily get to the locking coil unit mounting screws with the wipers screwed on, you can do this step first.

Remove the search wipers
search wiper locking coil/unit
remove search wipers

Pull the wipers off as mentioned above. Turn the wipers as needed to clear the search disc brackets.

Optional - unscrew search disc from shelf plate.
search disc bracket screws
remove search disc bracket screws
search disc flopped
tip search disc off shaft

If you need to clean off the metal shelf, it's easiest to unscrew the search disc brackets.

Unsolder the motor wires and remove the motor mounting bracket screws.
control unit motor wires
unsolder control unit motor wires

Unsolder the motor wires. Usually the wire length gives you a hint on which of the lugs they go on, but it doesn't matter unless the motor has multiple lugs. The late model games used motors that had extra lugs for 50 vs. 60 cycle AC power, so pay attention on those and make sure they are on the appropriate lugs for your country's power system.

Remove the two screws fastening the motor bracket to the metal shelf.

Remove control unit shaft assembly from game.
control unit assembly removal
remove control unit assembly

Pick up the entire control unit/motor assembly and take it out of the game. If the search disc is still fastened to the shelf, pull the shaft out of the search disc as you lift. When reinstalling, you'll want to hold the drag arms away from the cams as shown in the picture.

Remove search index ratchet/cams and clutch.
search index ratchet/cams
remove search index ratchet/cams
search index ratchet red dot
search index ratchet/cams red dot
search index ratchet clutch
search index ratchet clutch

Take off the search index ratchet/cams. Some games only have a metal ratchet with no cams attached.

For games with attached cams or a pin sticking out of the search ratchet, the ratchet must be reinstalled on the wipers correctly. Line up the red dot on the cams with the red dot on the wipers. If you forget or guess, you have a 50/50 chance of getting it right.

Remove the clutch washer and plate from the shaft. There may also be a thin washer between the clutch plate and the roll-pinned collar on the shaft. If the thin washer(s) are there, leave them if they are stuck or remove them if they will fall off.

Remove shaft roll/tension pin.
pin punch
1/8" pin punch
drive out pin
pin out, punch in

A pin punch has a nub on the end that fits into the pin and keeps it from slipping off. If you can't find one, a flat punch works too.

Support the shaft end on a block of wood or something to get the cams off the bench surface, then whack out the pin with the punch. The pin is 1/8" x 1" if you lose or mangle it.

Pull out punch and remove shaft pieces
remove punch
remove punch, pieces can slide off the shaft
timer cams
timer cams are connected together

Slide the pieces off the shaft. The only thing to watch out for is washers that are usually between the timer cam and replay cam clutch plates, and sometimes a washer between the replay cams clutch and the shaft collar.

Clean the pieces
clutch washer hole wear
clutch washer hole wear

Next up, clean up!

  1. clean the oil/grease off the shaft. You can put a light film of lube on the shaft as an anti-corrosive, but there's no need to lube the shaft...especially with something that gets dry/sticky.
  2. clean all the metal clutch plates and surfaces on the cams
  3. drop the good clutch washers in a bath of neatsfoot compound and let them soak

You may have worn clutch washers - don't worry about it unless they are really thin. Another kind of wear is expansion of the shaft hole caused by the white plastic cam inserts chewing up the leather. No big deal there, either.

dealing with the spring

Rebuilding the motor will be left for a different howto. Reassembly is basically reversing the order with the following suggestions:

  1. wipe oil off the clutch washers with a rag or paper towel. You do not want layer of oil on the surface of the leather - the clutch will slip too much.
  2. the metal nut/spring part that goes between the drag arm cam and the timer cam is a pressure adjust. Set it so the spring pressure is the least, and if the clutches slip, you can turn the nut to add more spring pressure to the cams.
  3. picture shows one way to compress the spring and get the drag arm cam on. I usually put a punch halfway in the hole to hold things together, then insert the roll pin from the other side and push the punch out with it.
  4. on mixers, I use thin channel-lock pliers to squeeze the pin in. Seems easier than pounding and it lets you wiggle the parts to get the pin into the shaft hole. However, the drag arm pins won't let you get pliers in for at least one pin, so you'll need to get the pin started and bang it in.
  5. you can use a heavy grease or super-lube on the drag arm cam edges, pins and drag arm stops. If you want to lube the bakelite cam edges, use a thin film only. Excessive lube will just scrape off.
  6. you have the search wipers off, so clean the contact plate. Scrub pad and alcohol gets to goo off, and a thin coat of super-lube will take care of it.
  7. clean the index unit, drag arm and back switches while the shaft is out...there's no easier access once the shaft goes back in.
  8. before you remount the search wiper lock unit, slip ring wipers, motor power wires and the entire bracket of CU switches, it's a good time to attach 120V directly to the motor and use a piece of alcohol-soaked cloth string in the slip ring wiper grooves to "floss" them clean. Hold the string in the groove, let the motor spin the wipers/hub.

Got any questions, send in a comment and I'll add to the above.