(Topic ID: 335234)

Coil Ratings and Replacements

By alkregha

11 months ago



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#1 11 months ago

In prepping to order a few new coils (for my 1962 Williams World Series), I found a few locations where I have coils installed that don't match my coil chart. I wanted to get some expert feedback on how critical this is, and a sanity check on why they may have been changed. The machine was repaired once by an external vendor (around 1996).

For each coil below, I compare the:
1) calculated resistance using this page https://www.daycounter.com/Calculators/Coil-Physical-Properties-Calculator.phtml and a set of calipers to roughly measure the Bobbin - I generally measured the OD of the coil sleeve which will be slightly smaller than the Bobbin diameter which will lead to slight underestimates of resistance.
2) the measured resistance (Fluke meter)
3) The "table resistance" (this page https://www.flippers.com/coil-resistance.html or https://www.pinballmedic.net/coilchart.html).

I also found this page to be good at explaining the goal: https://www.marcospecialties.com/pinball-parts-blog/coil-subs/

First one is the increment coil on the Run Unit (in the back insert assembly). Coil chart lists A 26-1100. Unit has an A 22-500 installed.

*A 26-1100: Calculated = 8.26 ohm; Measured = 9.5 ohm; Table = 9.2 ohm
*A 22-500 : Calculated = 1.54 ohm; Measured = 2.1 ohm; Table = ~2.3 ohm (only the A 22-550 is listed so should be slightly less than this)
*Conclusion: In this case, the A22-500 is going to have a higher current, leading to a stronger coil. My guess is, during the previous repair of this system, a gummed up stepper was the issue but the technician repaired it with stronger coils. Probably not the best approach, and now that I have cleaned the stepper, I will likely procure and retrofit with the original value.

Second one is the reset coil on the Run Unit (in the back insert assembly). Coil chart lists B 29-1600. Unit has a B1-26-800 installed.

*B 29-1600: Calculated = 24.25 ohm; Measured = 27.4 ohm; Table = 27.7 ohm
*B1-26-800: Calculated = 6.1 ohm; Measured = 6.5 ohm; Table = 7.7 ohm
*Conclusion: In this case, the B1-26-800 is going to have a higher current, leading to a stronger coil. My guess is, during the previous repair of this system, a gummed up stepper was the issue but the technician repaired it with stronger coils. Probably not the best approach, and now that I have cleaned the stepper, I will likely procure and retrofit with the original value.

Last one is the bat coil use to actuate the bat to hit the ball. Coil chart (and marco specialties) lists the correct part as H 23-870. Unit has H 24-1150, which also corresponds to the one used in deluxe baseball, batting champ, hit and run, pinch hitter, etc.

*H 23-870: Calculated = 4.35 ohm; Measured = NA - don't have; Table = no value
*H 24-1150: Calculated = 8.196 ohm; Measured = 6.8-7.0 ohm; Table = no value, but I see on the marco image a value of 8.5 ohms.

*Conclusion: In this case, I am guessing the repair technician could only track down the 24-1150, or assumed it to be correct based on other machines he had. The end result is a slightly weaker bat. I had mentioned in a previous post that I thought my bat was overly weak, even with the dial turned up. Additionally, I have read about how different pitch and bat machines had different ball sizes and bat types, which might be the reason for the two types. I will likely procure and retrofit with the original value.

Appreciate any feedback or guidance you can provide!

#2 11 months ago

Steppers - someone replaced 50 volt coils with the 24 volt coils that they had lying around. Order correct replacements per the chart.
Bat coil also likely replaced with whatever was handy.
Pinball Resource has the correct part.

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