Repairing the F-14 Beacon Motor

The F-14 pinball from Williams puts on a very flashy light show in attract mode including three rotating red, white and blue beacons mounted on the top of the backbox. During a game these beacons will light once you get three balls locked and are shooting for multiball mode. Unfortunately, the motor that turns these beacons is often non-functional. The problem is made even worse by the fact that replacement motor can be hard to find and can cost up to a $100 if you can find one. Fortunately, these motors can sometimes be repaired as one of the most common causes of failure is that one or both of the yellow wires that enter the motor housing break as a result of vibration and strain from the motion of the motor starting and stopping.

As with just about any pinball project, I started by first searching the rec.games.pinball (RGP) newsgroup through Google (see my links page for a link to take you to the Google search page). This search turned up several message threads on the topic of F-14 motor repair and I want to express my thanks to all of the people in that news group who offer their expertise to other hobbyists.

The beacons on my F-14 were completely non-functional when I got it. Not only did the beacons not rotate but the lights in the beacons didn't even light up. In fact the 4 amp slo-blo fuse that protects both the lights and the motor for the beacons would blow instantly indicating a short circuit somewhere. If it was in the motor then nothing would fix it short of rewinding the motor which would not be something I would feel capable of doing although one of the RGP posts I read indicated that the original motor manufacturer would rewind motors. Anyway, in my case the short turned out to be in the lights and not in the motor. Since the three lights and the motor are wired in parallel, in order to determine whether the short was in the motor or the lights, I disconnected (cut) the wires going to the motor from the connector that connects the output of the beacon circuit relay to the lights and motor. I then removed the bulbs from the light sockets and used my multimeter to test the light circuit and found zero resistence (or near enough as makes no difference). There was a short in the lights somewhere. After a bit of poking aound I found that the socket for one light was shorting out in the base. If I moved the lugs where the wires attach one way there would be no short, move them back and the short came back. Probably a result of corrosion and wear over time. Since these sockets are not easily replaceable I settled for moving the lugs until the short disappeard and then securing them in that position. Not the best fix and probably not permanent but I was anxious to find out if my beacons would work now that the short was gone.

No such luck. After reassembling the beacons in the back box and connecting the motor, the fuse no longer blew and the lights lit, but the motor didn't budge. (Pinball rule number one: Nothing is ever as easy as you hope it will be.). So back to the drawing board and time to see if the wires going into the motor were broken. The picutre below is a shot of the motor mounted on the beacon bracket after the assembly has been removed from the backbox. The motors originally had a housing that covered the motor but is was gone on my game.The round silver can at the bottom of the picture is the actual motor and the portion just above it is the gear housing. Also this is actually a picture of the motor after the repair since I forgot to take a "before" picture so if you are looking for the yellow wires you won't see them in this picture.

With the motor wires once again disconnected from the lamp circuit I used my meter in continuity test mode and as I wiggled the wires sometimes I would get a tone from the meter and sometimes not. Looks like I had the broken wire syndrome. Now came the fun part, seperating the motor from the gear housing. The next two pictures show the gear housing (left) and the motor (right) after being seperated.

The only thing holding them together is the shaft sticking out of the center of the motor which fits very tightly into the hole in the center of the gear box. To seperate them I used a regular head screw driver and placed the head between the motor and gear housing and twisted it and then kept repeating this in small steps going around the edge of the motor somewhat like the way you might open a paint can. Frankly it took a bit of guts but I figured the motor was useless anyway unless I could repair it.

Once I got the motor seperated I then had to pull the yellow wires out of the motor housing a bit in order to work on them. If you look at the picture above on the right you can see a small notch between the two wires. This is where they originally came out of the motor and where the wire was broken inside its insullation. You can also see this notch in the picture below.

In this picture I have trimmed the insulation back and have tinned the wires with solder. Since these wires were going to have to go back inside the motor housing I used the minimum amount of exposed wire and solder as possible.

Next I tinned and solder on two 18 guage wires to the yellow wires comming from the motor, again using the minimum amount of solder. I then covered the soleder joints with heat shrink tubing and stuffed the wires back into the house so that they protruded from the notch (not shown).

Since I wasn't sure whether I had fixed the motor or ruined it beyond repair and because I was getting tired of connecting and reconnecting the motor to the wires that go to the lights I added an extra connector for the wires going to the motor.

Now cam the moment of truth. I mounted everything back into the backbox, turned on the game, put it into test mode, and low and behold the beacons worked!