(Topic ID: 289579)

Bally flipper coil question

By Sea_Wolf

6 months ago


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  • 18 posts
  • 5 Pinsiders participating
  • Latest reply 6 months ago by Sea_Wolf
  • Topic is favorited by 2 Pinsiders

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#1 6 months ago

Just wondering what the chances are that the 2 AF-25-500 coils could be different in power. The game when I picked it up had a generic replacement coil on the the left (AF-25-500) and the original coil (AF-25-600) on the right. I decided I liked the extra power on the left flipper so I ordered a replacement coil from Marco and installed it.

Both are opening the EOS at the same point but the ‘Pincoil’ replacement from Marco is just a bit weaker than the generic one on the left and it’s definitely noticeable.

Just wondering if the generic one on the left is possibly mid-labeled or if anyone else has had a similar issue. I just grabbed a 9-volt for my multi meter and would love any advice. Thanks. Danny

#2 6 months ago

I also should have mentioned that I just rebuilt both flippers. New bats, everything. Thanks again for any advice.

#3 6 months ago

Here are some things that can cause differences in flipper strength when all parts are new, besides what you already mentioned.

If you haven't done this yet, you can check your coils (out of circuit) with a multi-meter to see how many ohms you have on the power windings. If the ohm reading between the two coils is much different, the one with the lower ohm reading will generally have the stronger kick.

If the return spring tension is different on the two flipper assemblies, the flipper with the stronger return spring will have a weaker power stroke.

If the plunger pivot on the flipper crank is binding on one crank but not the other, the crank with the binding pivot will seem weaker (yes you can have a binding pivot on a brand new crank).

If the flipper crank is installed on the shaft of the flipper such that the bushing of the crank is too tight against the bottom end of the nylon sleeve that runs through the PF, that binding point will make the flipper weaker. If one flipper has good end-play between the crank and the sleeve bottom, and the other flipper is too tight, then the tight flipper will seem weaker.

If the coil mounting bracket for the flipper coil is positioned such that the plunger path into the coil is not lined up quite right, the plunger can bind against the inside wall of the coil sleeve. This mis-alignment can sometimes be caused by attaching the flipper crank onto the flipper shaft too far down (ie, towards the end of the shaft). If one flipper plunger is binding in this way and the other isn't, then the binding flipper will seem weaker. You may not notice this type of binding problem unless you check the action of the flipper assembly while the PF is in the normal playing position.

- TimMe

#4 6 months ago
Quoted from TimMe:

Here are some things that can cause differences in flipper strength when all parts are new, besides what you already mentioned.
If you haven't done this yet, you can check your coils (out of circuit) with a multi-meter to see how many ohms you have on the power windings. If the ohm reading between the two coils is much different, the one with the lower ohm reading will generally have the stronger kick.
If the return spring tension is different on the two flipper assemblies, the flipper with the stronger return spring will have a weaker power stroke.
If the plunger pivot on the flipper crank is binding on one crank but not the other, the crank with the binding pivot will seem weaker (yes you can have a binding pivot on a brand new crank).
If the flipper crank is installed on the shaft of the flipper such that the bushing of the crank is too tight against the bottom end of the nylon sleeve that runs through the PF, that binding point will make the flipper weaker. If one flipper has good end-play between the crank and the sleeve bottom, and the other flipper is too tight, then the tight flipper will seem weaker.
If the coil mounting bracket for the flipper coil is positioned such that the plunger path into the coil is not lined up quite right, the plunger can bind against the inside wall of the coil sleeve. This mis-alignment can sometimes be caused by attaching the flipper crank onto the flipper shaft too far down (ie, towards the end of the shaft). If one flipper plunger is binding in this way and the other isn't, then the binding flipper will seem weaker. You may not notice this type of binding problem unless you check the action of the flipper assembly while the PF is in the normal playing position.
- TimMe

Thanks TimMe for listing all the possible causes. I’ll go through your tips one by one tonight.

The only one that I’m pretty sure is ok is where the flipper crank is attached but I’ll double check again.

#5 6 months ago

If you'd like to test relative coil strength, swap them left for right.

#6 6 months ago
Quoted from HowardR:

If you'd like to test relative coil strength, swap them left for right.

Thanks Howard. That makes total sense but I’m trying to be lazy to not have to desolder and resolder.

The former owner snipped the wires to the coil on the left flipper, that there’s not much length left.

#7 6 months ago
Quoted from TimMe:

Here are some things that can cause differences in flipper strength when all parts are new, besides what you already mentioned.
If you haven't done this yet, you can check your coils (out of circuit) with a multi-meter to see how many ohms you have on the power windings. If the ohm reading between the two coils is much different, the one with the lower ohm reading will generally have the stronger kick.
If the return spring tension is different on the two flipper assemblies, the flipper with the stronger return spring will have a weaker power stroke.
If the plunger pivot on the flipper crank is binding on one crank but not the other, the crank with the binding pivot will seem weaker (yes you can have a binding pivot on a brand new crank).
If the flipper crank is installed on the shaft of the flipper such that the bushing of the crank is too tight against the bottom end of the nylon sleeve that runs through the PF, that binding point will make the flipper weaker. If one flipper has good end-play between the crank and the sleeve bottom, and the other flipper is too tight, then the tight flipper will seem weaker.
If the coil mounting bracket for the flipper coil is positioned such that the plunger path into the coil is not lined up quite right, the plunger can bind against the inside wall of the coil sleeve. This mis-alignment can sometimes be caused by attaching the flipper crank onto the flipper shaft too far down (ie, towards the end of the shaft). If one flipper plunger is binding in this way and the other isn't, then the binding flipper will seem weaker. You may not notice this type of binding problem unless you check the action of the flipper assembly while the PF is in the normal playing position.
- TimMe

I have the multimeter at hand but had a quick question. Obviously power off but do I first need to disconnect a wire or 2 on each flipper coil before testing? I was assuming that’s what you meant by out of circuit.

Or can I just test the lugs with the power off and no disconnects and get a true reading? Thanks

#8 6 months ago

Early pinball machines (of every brand) that have directly controlled flippers using the EOS to break the high current circuit, rely very heavily on accurate and careful cleaning and adjustment of the EOS switches. This is the most critical part to having flippers working well in these machines.

You need to adjust the contacts close enough to shunt power to the pull side of the coil as long as possible BUT make sure the EOS is able to open reliably at the end of stroke to prevent burning out of the coil.

Naturally there are many other considerations such as flipper bush wear and plunger/sleeve wear but, as you have replaced all of these, it probably comes down to SUPER critical EOS adjustment or replacement of you haven't already?

#9 6 months ago
Quoted from pins4u:

Early pinball machines (of every brand) that have directly controlled flippers using the EOS to break the high current circuit, rely very heavily on accurate and careful cleaning and adjustment of the EOS switches. This is the most critical part to having flippers working well in these machines.
You need to adjust the contacts close enough to shunt power to the pull side of the coil as long as possible BUT make sure the EOS is able to open reliably at the end of stroke to prevent burning out of the coil.
Naturally there are many other considerations such as flipper bush wear and plunger/sleeve wear but, as you have replaced all of these, it probably comes down to SUPER critical EOS adjustment or replacement of you haven't already?

Thanks.
Yes I just rebuilt both flippers. New EOS switches, bushings, flipper bats, coil stops, etc....

#10 6 months ago
Quoted from pins4u:

Early pinball machines (of every brand) that have directly controlled flippers using the EOS to break the high current circuit, rely very heavily on accurate and careful cleaning and adjustment of the EOS switches. This is the most critical part to having flippers working well in these machines.
You need to adjust the contacts close enough to shunt power to the pull side of the coil as long as possible BUT make sure the EOS is able to open reliably at the end of stroke to prevent burning out of the coil.
Naturally there are many other considerations such as flipper bush wear and plunger/sleeve wear but, as you have replaced all of these, it probably comes down to SUPER critical EOS adjustment or replacement of you haven't already?

Also, I’ve got it adjusted to where both EOS switches open just enough to break the circuit. Thanks for the post.

#11 6 months ago

With the power off and wiring intact, I tested both flipper coils and the weaker one on the right tested right at 3.2 ohms and the stronger one on the left tested right at 1.7 ohms.

That makes sense from what TimMe suggested but I just wanted to make sure I’m getting a true reading. I’ve read in other posts that in order not to have other coils down the line get involved that some wiring may need to be disconnected.

Last thing, the weaker flipper on the right works well and may be performing correctly for its rating but the flipper on the left is just extra powerful but I like it. Maybe too strong? I originally purchased and installed the weaker AF25-600 flipper coils that were what the game originally called for but i wanted more oomph. Both flippers were equally lacking enough power for my liking. Now I just want to get them equal again but stronger than the originals.

Thanks for the help.

#12 6 months ago

It's best to detach one solder lug of a coil so that you are testing it totally out of the circuit. Since you only need to check the high-current winding of your flipper coils, you won't need to unsolder all the wires. If you are not sure which two lugs represent the high-current winding, look at the magnet wires coming up from the coil winding, where they attach to the solder lugs. The two lugs with the thicker magnet wires on them are the two lugs for the high-current winding. Detach the game wiring from one of those lugs to get the most accurate ohm reading from the coil.

If the two readings you posted are really correct, that is a pretty big difference in power. It surprises me that those two coils are the same part number. The part number literally represents the wire gauge and the number of windings, and so I would not expect two coils that are wound the same to be so different.

I would not consider those two coils to be a matched pair, and I would not put them in the same game. If you don't want to replace one of the coils with something that creates a better matched pair, you can compensate for the power difference by adjusting the EOS switch of the stronger coil to open sooner than the EOS switch of the weaker coil. That will make the two flippers have the same power level, although it accomplishes this by making the stronger flipper become less strong.

In your situation (again, assuming your ohm readings are correct), if you want to make the weaker flipper stronger, you'll probably need to put in a different coil that matches the ohm reading of your strong coil more closely.

- TimMe

#13 6 months ago

if you want to keep the stronger/weaker flipper coil setup but have the stronger coil a little weaker you can add in a ceramic resisitor to the EOS circuit, maybe a 5W 1.5ohm to start?

#14 6 months ago

Some additional info on this - I got curious so I just checked the high-current windings of the spare Bally flipper coils I keep on hand. All my 25-500s landed at 3.1 ohms. All my 25-600s landed at 3.8 ohms. So your flipper coil with a high-current winding that is 1.7 ohms seems to be the odd one out.

- TimMe

#15 6 months ago
Quoted from TimMe:

It's best to detach one solder lug of a coil so that you are testing it totally out of the circuit. Since you only need to check the high-current winding of your flipper coils, you won't need to unsolder all the wires. If you are not sure which two lugs represent the high-current winding, look at the magnet wires coming up from the coil winding, where they attach to the solder lugs. The two lugs with the thicker magnet wires on them are the two lugs for the high-current winding. Detach the game wiring from one of those lugs to get the most accurate ohm reading from the coil.
If the two readings you posted are really correct, that is a pretty big difference in power. It surprises me that those two coils are the same part number. The part number literally represents the wire gauge and the number of windings, and so I would not expect two coils that are wound the same to be so different.
I would not consider those two coils to be a matched pair, and I would not put them in the same game. If you don't want to replace one of the coils with something that creates a better matched pair, you can compensate for the power difference by adjusting the EOS switch of the stronger coil to open sooner than the EOS switch of the weaker coil. That will make the two flippers have the same power level, although it accomplishes this by making the stronger flipper become less strong.
In your situation (again, assuming your ohm readings are correct), if you want to make the weaker flipper stronger, you'll probably need to put in a different coil that matches the ohm reading of your strong coil more closely.
- TimMe

Thanks. I will desolder the one wire and retest this evening and post what I get.

The coil with the lower resistance was installed by the former owner and he or somebody else was pretty rough on this pin. The wrapping on the coil is generic looking orange and says AF-25-500 and doesn’t seem like it was messed with but who knows.

If it comes down to it, I’ll adjust the EOS switch on the left to open a bit earlier. Thanks for the idea.

#16 6 months ago
Quoted from Rikoshay:

if you want to keep the stronger/weaker flipper coil setup but have the stronger coil a little weaker you can add in a ceramic resisitor to the EOS circuit, maybe a 5W 1.5ohm to start?

Thanks. Another option and that’s always a plus.

#17 6 months ago
Quoted from TimMe:

Some additional info on this - I got curious so I just checked the high-current windings of the spare Bally flipper coils I keep on hand. All my 25-500s landed at 3.1 ohms. All my 25-600s landed at 3.8 ohms. So your flipper coil with a high-current winding that is 1.7 ohms seems to be the odd one out.
- TimMe

I just wonder if it got mislabeled somehow from whoever made it. It’s really powerful but I have to admit I like it. If you fully pump the left flipper and you hit the center target it comes back at you like a bullet. I’ve actually ripped the spinner with that left flipper and it spinned like you couldn’t believe.

I went ahead and ordered a new AF 25-500 coil today from PBR so I can find out.

Really appreciate all the help.

#18 6 months ago

TimMe . Well I desoldered one of the thicker copper wires on each coil and re-tested and it was pretty much the same result. 1.6 ohms on the left flipper coil and 3.3 on the right flipper coil.

I’ve got the new 25-500 coil on the way so I’ll wait to mark this thread resolved but I appreciate all the help and the gained knowledge.

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