Thursday, May 19, 2011

MM flipper repair

When repairing a pinball machine, always check that genuine pinball parts are used.

I'm restoring a Medieval Madness. When the game came in I played a few games to have an idea how it felt, what parts didn't work well (so I knew I had to pay extra attention to them when I stripped the playfield down).

One of the things that I noticed was that the flippers were really weak. I could barely get a pinball up a ramp. But I assumed the assemblies were just worn and would replace them anyway whilst shopping the game.

I always replace the plunger/link, flipper bushing, coil sleeves and the coil stop.
The coils themselves were still good, the sleeve didn't stick into the coil and could be removed easily.
On this particular game I also replaced on end-of-stroke switch as a part of the long blade was broken and the flipper link would stick behind it, leaving the flipper bat in the up position.

But what this post is about - I noticed something really weird when replacing these parts. The flipper return springs were not pinball parts !

Although they looked similar, they were much larger and thicker than what has to go on there.

Here's an image of the large spring that was installed and the spring that should go on there. The larger spring is too strong, probably they caused the flippers to have not enough power. Had original springs been used the game would have played a lot better. Small things like a 50 cents spring can make or break how well a game plays.

The correct springs I had in my spare toolbox, in which a lot of small spare parts (springs, all types of screws, ..) are laying loose.
When I had installed the new spring and checked its tension, I noticed something was inside the little spring ?! See this picture - it's in the middle of the extended spring.

Quiz time: do you know what was hidden inside the spring ?
And no it's not an airgun pellet (although it looks like it), it is a part used on a pinball machine.

Btw when installing the new flipper return springs and the bushing, I noticed the base plate of the right flipper was of a different type than that of the left flipper.
It was of an older type of WPC pinball, as it didn't have 2 extra holes to mount the little spring in. It was the type of base plate that's used on the older wpc games that had a conical flipper return spring that went around the flipper plunger.
I noticed it was different but didn't think much of this. As I replaced the coilstop and flipper link I thought it wouldn't matter anyway - I should have known better...

When the playfield was totally assembled and I played my first game I noticed my mistake. The right flipper had less travel, whilst they were both aligned to be in the same position when down, in the up position the right flipper didn't come as high as the left flipper.

Big problem.. both flippers really need to act the same whilst playing.
My first thought - as you can see on the first picture was that I had used a generic part for the left flipper. The plastic link is a slightly different shape than on an original Williams part. Thought this maybe had a small size difference with another link which cause the left flipper to raise higher.
As the flipper assembly acts like a lever, a small change in distance of how much the plunger travels (because of a different coil stop for example, or plunger link), will be magnified at the end of the flipper tip.
Removed this whole plunger and link assembly and put a new, correct type in.
No difference, the right flipper still didn't raise as much as the left.

Then I remembered the difference in base plates, and I remembered these were slightly different and you needed to use the correct coil stops on them too (which I didn't have, only have 1 type of generic coil stop in my spare parts).
So I disassembled the whole right flipper again and replaced the base plate with a correct, more recent type.

The differences between both base plates are barely noticeable. Visually they look the same, same size, coilstop and flipper are mounted on the same distance, ..
But they are not the same.
You can identify them: there are less holes in the upright metal where the flipper return spring hooks in, and the flipper bushing is secured with screws that have loose nut on one type, while on the other type the nuts are glued onto the flipper base plate.
See the difference between the first (good) and third picture (wrong plate) - in the first the spring is stuck in a hole to the side, in the third picture there was no such hole present, it was stuck in a hole in the center.

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