Like the drag arm stops, this problem is also subtle, and to some extent theoretical. The mixer discs randomize the game and control the odds such that the game operator will make money over the long term (this is known as percentaging, and is why Las Vegas exists).
The mixer operation is pretty simple. When a coin is played, the
mixers are released to spin by activation of the mixer latch coil(s).
After some time (related to those cams that
the drag arms where mucking with), the mixer latch coils release and the
mixer lever arms slide up, the index pins catch the mixer discs and stop them
The sneaky bit is the lever arms themselves slide at different times relative to each other, thus causing the discs to stop at different times.
Mixer Roller and Cam
lever arm roller
a roller on the lever|
arm which the cam rides on
Anyway, here we have a roller on the lever arm, and we can see that the
roller is not perpendicular to the arm. In fact, it wobbles around,
but in actual use it is pushed back so the cam is riding on it's surface
at an angle.
|Well, obvious wear...|
Of course, the main question about wobbly rollers is "so what". Well, let's
take a look at the cam that rides on this roller....though this is NOT
a common problem.
Part of the reason for the excessive wear is that the cam edge is no longer flat...it's got a bevel caused by running along the skewed roller surface.
So what to do about it. Well, if the cam still works, I guess you stick it back in and forget about it. The difference between the original steep hill and the worn slope doesn't really matter at all - it may cause the rotor to spin 1-2 additional positions before it is stopped, but that's about all.
Another option is to replace the bakelite cam with one from a parts machine. If you are truly
desperate, you'd have to make a new cam. John found a source for phenolic canvas sheet
material - www.professionalplastics.com, but you'd only need a tiny piece. Probably easier to go to a retail plastic place like Tap Plastics, get a piece of scrap acrylic and carve out your own.
|mixer arm diagram|
Notice how the arms (15 - although the one they point at is different from the rest) slide in a slot in a metal plate (32). The diagram shows the arms in their "stop the disc" position. You can't see the notch. However, if you imagine the arm sliding down, the notch (see picture below) will catch on the plate and keep the arm from sliding back up.
|no notch any more|
There are two solutions - the correct one and the one the operators normally chose. The correct one was to replace the arm. Since that costs money, the operators generally did what you are about to do..they filed the metal to recreate a nice notch. However, there are limits.
If you remove too much metal, it won't work. Either the arm will slide
up far enough to stop the disc before it should, or the cam will push the
arm off the notch before it should.
filed lever arm
|This guy overdid it.|
The only solution at this point is to replace the arm or replace the metal by welding it. I saw a GI-Joe junior welding kit at a hardware store for about $50. It uses some stuff called Mapp Gas and oxygen, and I tried it. It produces a nice little flame that is good enough to make the metal red-hot, and I used some kinda brazing rod to form a big blob of metal where there was no metal before. The tricky bit is that metal is a liquid when it's melted (duh), so you need to figure out a way to hold the arm and apply the new metal so it doesn't run away in a direction you don't want. I used a bench vise. The other nasty bit is the torch itself is shooting out a flame under pressure, so it wants to push the liquified material away. A little experimentation and will eventually get a blob of metal where you want it. Don't try and be neat...you grind off the excess after it has cooled using you trusty moto-tool with cutter attachment.
The open question is how soft is brazing material...will it wear away
much faster than the original material?