Converting Classic Bally/Stern Machines To WPC Style Flipper Assemblies

2 January, 2009 (22:41) | Restoration Logs | By: admin

Earlier this year I repaired a Meteor pinball machine for a fellow who contacted me through my old website. He had purchased the game on Ebay and had it shipped to Edmonton. I won’t mention what his total cost was on the machine but suffice it to say that it was too much. I didn’t have the heart to tell him I had purchased 2 Meteor machines locally only a couple of months prior for a really good price.

In any event… this was a good opportunity to get some Meteor experience before restoring my own so I agreed to do some work on the machine. As usual it turned out to be much more work that I was expecting but that’s a story for another day. Part of the work I performed was to install new WPC style flipper assemblies and that’s what I’m going to cover here. In the future I will probably write a more detailed article on the process but in the mean time this should provide enough information to perform the conversion yourself.

This is what the finished product looked like. Two brand new flipper assemblies installed complete with new coils, EOS switches and capacitors. A thing of beauty.

I bought all of the parts for this conversion from Pinball Life . I can’t recommend them highly enough. I purchased left and right WPC style full flipper assemblies with FL-11630 coils. These are the williams "red" coil as used in games like Taxi. Initially I was concerned that these coils may be too strong but they turned out to be just perfect. Stronger than original but not so strong that things are going to break or the ball is going to be hitting the glass a lot. The fact that the voltage is slightly lower than what it would be in a newer game likely helped.

I also had to order normally closed end of stroke (EOS) switches for both flipper assemblies. The WPC flipper assemblies come with normally open switches and this modification required normally closed EOS switches. Additionally the switches also need to have high current contacts. The EOS switches that come with the assemblies would burn up in a matter of a few flips if used in this circuit. Keep this in mind because it would be possible to flip the switch that comes with the assemblies and use it as normally closed. I ordered several different EOS switch styles so I could determine which would be the best fit for this application. In the end all of the styles I ordered would have worked. Some with modification and some without. I chose to use the cheapest ones for this project. They worked out perfectly and I’ll use them again in the future. With parallel wound coils and a capacitor across the end of stroke switch there is not a lot of spark at the EOS switch anyway.

This is what the original coil wiring looks like. Note that the original coils are series wound. This means that the 2 coils on the spool are wound in series with the center lug being common. The coils that I’m going to be using for this conversion are parallel wound meaning that the 2 coils on the spool are wired to the lugs in parallel. A full explanation of series vs. parallel wound coils is beyond the scope of this article. More information can be found here as well as many other sources on the web.

Here we see the new parallel wound FL-11630 coil. Note that the common lug is on the left when viewed from this angle.

The first step was to remove the existing flipper assemblies. There will be 2 wires (or series of wires connected together) coming into each flipper assembly. I disconnected these and removed the complete assemblies as one unit after removing the flipper bats.

At this point I needed to determine which wire in each set was the positive side of the circuit and which the negative. I determined this by looking at the schematic but confirmed with a meter just to be sure.

This is what the original assemblies looked like. One difference to note is the orientation of the coil. The original assemblies have the coil connections facing the coil stop. The new assembly has the coil connections facing the opposite direction. This is because there is more vibration energy transferred to the connections with them closest to the coil stop. Reversing the coil is a good modification to make as part of a flipper rebuild. Even when reusing the original coil.

There is a diode missing from this coil.

This is what the new flipper assemblies look like in their original form. Note the normally open switch contacts.

Here we see the same flipper assembly with normally closed EOS switch installed.

I had to modify the switches I chose to use slightly to work in this configuration. One of the switch leaves was too long but fortunately I was able to cut it to length and it worker perfectly. I installed the switch, measured where to cut and cut the switch leaf with sharp side cutters.

This is the switch after shortening.

Another problem was that the switch contacts were not actually making contact in their normal position. This is because the switch leaves were perfectly straight. I bent both leaves with a switch adjustment tool so they were making good contact in their normal position.

The last step was to clean the contacts with a file and the switches were ready to go.

Here you can see where the switch leaf had to be cut to allow clearance for the flipper pawl assembly.

New EOS switch installed and tested.

The next step was to install the new assemblies. I adjusted their position to what I thought was ideal and screwed them down. The exact position the the assemblies is not crucial so long as they’re not interfering with anything else and they’re able to be secured tightly to the playfield with screws in all available mounting holes. Just be sure to not confuse left and right. The assemblies are unique for each side.

In my case I added the additional screws later. The original assemblies used 4 and the new assembly has 8 mounting holes. Use them all if possible.

The next step is to install the wiring. I’m switching to a different type of coil so the orientation of the wires will be different. I find it easiest to isolate the 2 wires (or series of wires connected together) for each flipper and determine their polarity with a volt meter. From there it’s pretty easy to connect everything following these steps:

1. Start by connecting wires to each of the end of stroke switch leaves. Make them long enough to reach the coil lugs. This is also a good time to install a new 2.2K 250V capacitor across the end of stroke switch contacts. Note: In my pictures I’ve doubles the wires for each end of stroke switch contact for better current flow.

2. Connect the positive wire the the common coil lug. This is the one that has 2 coil wires attached to it. It’s also the outside lug nearest to the bands on the diodes.

3. Connect the negative wire and one of the end of stroke switch wires to the other outside coil lug.

4. Connect the other end of stroke switch wire the the center coil lug.

Now you should be ready to adjust the EOS switch and position the flipper bat.

This is what the other flipper looked like when finished. This one shows multiple wires coming in for the positive and negative connections. One lug even has 2 different colored wires.

An important consideration to make when doing this conversion is the length of the flipper bat shafts. In this case I’m converting a Stern Meteor machine. Stern used 2 different flipper styles throughout their production. The earlier style uses a flipper bat with a shorter shaft than the newer style. This flipper bat is seen on the left in this picture. Unfortunately this flipper bat is too shot to work with the new WPC style flipper assemblies. If you’re going to make this conversion on one of these games you’ll need to replace the flipper bats. The newer style Stern flipper bats are long enough (seen on the left).

I had the longer flipper bats on hand but you should be able to purchase them from Pinball Resource or any of the other larger pinball parts suppliers.

If you’re using these flipper bats it’s important to keep the jaws on the flipper pawl from closing into the gap at the bottom of the flipper bat shaft. If one of the jaws on the pawl closes into this gap it won’t be able to hold the flipper bat firmly enough. It’s also a real pain to try to re-open the jaws and get the flipper bat back into position. It took quite a bit of adjusting to get the new mechanisms working perfectly with the old flipper bats but in the end it played GREAT!