I need to replace the flipper EOS switch on my left flipper of #mr-and-mrs-pac-man. As you can see, these contacts are fried. One of them was so damaged from arcing that it fell off! I want the contacts on the new switches I buy to last longer than these did. And I want to do it for all of my early SS pins. The question is, how can I reduce the arcing that damages the contacts, reduces the power to the flipper solenoids and causes weaker flipper performance?

flipper_eos_contact_missing (resized).jpg

flipper_eos_contact_close_up (resized).jpg

In the picture above it appears like the metal from the lower contact was deposited onto the upper contact.

I have done some research about adding a capacitor to flipper EOS and cabinet switches. I have read that it only matters on later 80s games and newer that use parallel and not series solenoids. I have read that 2.2 uF capacitors on the EOS switches and .1 uF capacitors on the cabinet flipper switches will help. I have read that capacitors will not help at all on early SS pins. I don't know what to believe.

Bay Area Amusements has these "225K 50V Axial Capacitor - Early Williams EOS Switch Cap[s]"

http://bayareaamusements.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=CA-225

I don't think I have ever seen capacitors on early Williams pins and I haven't read anything about 225K uF capacitors used for flipper EOS switches.

I know I can upgrade the solenoids/flipper assemblies, but I have too many pins to do that. I don't need to eliminate the arcing entirely. I just want to reduce the amount wear on the contacts and reduce the amount of time that I have to polish these contacts with a Dremel and #443 wire brushes.

So, what is the real story here? Is there a way I can reduce the arcing? I want the pins I have on route to have powerful flippers and I don't want to have to spend a lot of money to do it.

I did some research for non-pinball solutions and found that there is something called a 'snubber' circuit that reduces the arcing.

But first I want to understand what, exactly, is causing the arcing. Okay guys, please work with me here. I am not an electronics expert so I could have some of the following wrong. Please correct any mistakes I make.

Electricity flows into the coils (wires) of the high power flipper solenoid when the cabinet flipper button is pressed and when the EOS switch is closed. This creates a strong electro-magnetic field. The high power solenoid is deactivated when the flipper button is released or when the flipper button continues to be pushed and the flipper moves to the 'up' position, opening up the EOS switch. Current then flows to the low power solenoid (hold solenoid) when the EOS switch is opened. This is better explained here:

http://stevekulpa.net/pinball/bally_flipper1.htm

As I understand it, and, as I mentioned above, I may not understand it, this is how the arcing is created. The 43 to 48 Volts DC causes some arcing as the EOS switch opens. More arcing occurs when the current to the solenoid is turned off and the EOS switch closes. The electro-magnetic field collapses and that creates an electrical current with high voltages - much higher than the 43 to 48 Volts DC used to power the flipper solenoids causing arcing. This is why solenoids on solid state pinball machines have diodes. They prevent the solenoid voltage and the high 'kickback' voltage from reaching the sensitive transistors on the driver board that control the solenoids.

An RC 'snubbing' circuit can be added that will reduce the arcing. The circuit is simple with a capacitor in parallel to the EOS switch and a resistor in series with the capacitor, thus the name 'RC', not to be confused with model RC cars or planes. In layman's terms, that's me, the capacitor goes across the EOS switches and the resistor goes 'inline' next to the capacitor.

This page shows the circuit and some guidelines for determining the values of the resistor and capacitor:

https://www.idec.com/language/english/AppNotes/Relays/contact_circuit_protection.pdf

Resistor Value = .5 to 1 Ohm per Volt
Capacitor Value = .5 to 1 uF per Amp

Bally pins use 43VDC and Williams pins use 25VDC and, later, 50VDC. So, the resistor value should be 22 to 43 Ohms for Bally and 13 to 25 Ohms for Williams @25VDC and 25 to 50 Ohms for Williams @50VDC. I am unsure of the Wattage.

Flipper solenoids draw approximately 4.3A per Steve Kulpa (http://stevekulpa.net/pinball/bally_flipper1.htm). So the capacitor value should be 2.2 to 4.3 uF.

As Quench mentioned:

Has anyone tried an RC 'snubber' circuit to reduce arcing? Results?

I was trying to figure out the wattage needed for a resistor in the RC circuit and came up with this:

P = I x V
P = 4.3A x 25V
P (Watts) = 107.5

107.5 Watts? That can’t be right, can it?

Thanks Ken. That’s what I am going with.

Thanks guys for the good info!

I have ordered the following from GPE for the grand experiment:

Caps For Flipper EOS Switch:

Part Number CPA-2.2uF-250V Capacitor, Axial Polyester. These are the yellow caps, equivalent to the ones that Williams used.
Part Number CPR-2.2uF-250V-J Capacitor, Radial Polyester, 2.2uF, 250V, 5% Metalized Polyester Film. These are smaller and probably lighter.

Cap for Cabinet Flipper Switch:

Part Number CCD-0.1uF-500V-P5 Capacitor, Ceramic Disc, 0.1uF, 500V

Resistors For Both Flipper EOS Switch and Cabinet Switch:

Part Number RN70D33R2F, Resistor Metal Glaze, 33.2 Ohm, 3/4 Watt 1% These are really 2 Watt resistors downgraded to 3/4 Watt for Mil-Spec purposes.
Part Number RC5W-27-SQT Resistor, 27 Ohm, 5 Watt, SQT, in case 2 Watts isn't enough and parts begin to fry.

Both resistors are supposed to be flame resistant so I don't expect to be starting any fires. But there could be some smoke! Can you tell that I like to experiment?

I plan to somehow attach the caps to the EOS switch with zip ties, silicone or ???

I will be reporting back how well these parts reduce arcing in several different configurations.

Oh, that’s bad, really bad. I like it!

Thanks for asking. I haven't gotten to it yet.

I got the parts from GPE:

Arcing Reducers (resized).png

Caps For Flipper EOS Switch:

Part Number CPA-2.2uF-250V Capacitor, Axial Polyester. These are the yellow caps, equivalent to the ones that Williams used.
Part Number CPR-2.2uF-250V-J Capacitor, Radial Polyester, 2.2uF, 250V, 5% Metalized Polyester Film. These are smaller and probably lighter.

Cap for Cabinet Flipper Switch:

Part Number CCD-0.1uF-500V-P5 Capacitor, Ceramic Disc, 0.1uF, 500V

Resistors For Both Flipper EOS Switch and Cabinet Switch:

Part Number RN70D33R2F, Resistor Metal Glaze, 33.2 Ohm, 3/4 Watt 1% These are really 2 Watt resistors downgraded to 3/4 Watt for Mil-Spec purposes.
Part Number RC5W-27-SQT Resistor, 27 Ohm, 5 Watt, SQT, in case 2 Watts isn't enough and parts begin to fry.

I will try to get to the experimenting soon.

Good idea, but you are too late Ken. Experiment completed!

All tests were done using a Williams 1980 Black Knight.

Experiment 1: Part Number CPA-2.2uF-250V Capacitor, Axial Polyester, only.

There was a big, huge suppression of any arcing. There would occasionally be some visible arcing, less than without the capacitor, but most of the time there was little or no spark.

DSCF3723 (resized).JPG

Experiment 2: Part Number CPA-2.2uF-250V Capacitor, Axial Polyester, only AND Part Number RN70D33R2F, Resistor Metal Glaze, 33.2 Ohm, 3/4 Watt 1% These are really 2 Watt resistors downgraded to 3/4 Watt for Mil-Spec purposes.

The arcing was much worse with the resistor and capacitor than with the capacitor only! It shouldn't be according to what I read about RC snubbing circuits, but that is what I saw and I'm sticking to it!

DSCF3724 (resized).JPG

During the second experiment the resistor didn't even get warm, even with constant flipping.

I never really paid attention to this, but you are absolutely right @quench. Thanks for the correction.

So, I will be putting the capacitors on all of my SS flipper EOS switches.

I just realized that I didn't test the flipper cabinet switches with the ceramic capacitors. Maybe I will do that experiment later.