Tech: Serial vs. Parallel Flipper Coils

[LexingtonVAPin]

Revisiting this old thread:
https://groups.google.com/g/rec.games.pinball/c/7w_ylCWpvHo/m/sPUKBGMuEAAJ

I am trying to figure out how to tell whether a coil is serial or
parallel (without unwinding it).

Early flipper coils had part numbers that were descriptive like
23/600-30/2600. That would indicate #23 wire 600 turns, and #30 wire
2600 turns.

Since they are two different diameter wires, aren't they parallel?

One person said that if there are four different wires, they are
parallel. Aren't there always four wires, even if serial? Williams Sys
6 Firepower looks like two different diameter wires.

Are parallel coils wound with the power coil on the inside and the hold
coil on the outside?

Serial are wound from one end to the other with a tap part way through?

The only thing I can tell is that later pins disconnect the power
winding (hence the two diodes).
The earlier ones short out the hold winding, then opens - keeping both
the hold and power energized. Both fields collapse simultaneously, so
only one diode needed.

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[cfhatprovidedotnet]

easiest way is to look at the diode. if there's two diodes,
it's parallel wound. if there's one diode, it's serial wound.
All EM flipper coils (no diode) that i have ever encountered
are serial wound.

[LexingtonVAPin]

That is what I always thought too.

In looking at how these coils are wired, in one setup, the EOS switch
shorts out the hold coil. When it opens up, both the power and hold
coils are connected. When the flipper switch is released, both windings
collapse at the same time, so only one diode - across both - is needed.

In the newer setup, the EOS switch is connected in series with the power
coil. On the flip, both power and hold coils are initially powered.
When the EOS opens, the power coil is disconnected and a diode is
required for the back EMF.
The hold coil stays powered. When the flipper switch is released, the
separate diode is required for the hold coil.

I am looking at two coils: 11630 and 25-500/34-4500. The obvious
difference between the two is that the 11630 is wired with both coils to
the left lug (viewed from the plunger side), power to the center and
hold to the right.
With the other coil, two wires go to the center. Power to the left and
hold to the right. Both coils have two diodes.

The 25-500/34-4500 is used in a Bally could be a parallel coil, but they
never used a cap on the EOS or flipper switch (that I am aware of).

I looked at a Gorgar. Williams supposedly used serial coils. It is a
19-400/30-750. It looks exactly like the 25-500/34-4500 in that the
power connections are left/center and the hold is center/right. A
single diode is on it. It is wired just like the early Bally, with the
EOS shorting out the hold coil.

What makes a coil serial vs parallel?

https://flic.kr/p/2kmRDZk

https://flic.kr/p/2kmR5eZ

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[seymour.shabow]

LexingtonVAPin wrote:
>
> The 25-500/34-4500 is used in a Bally could be a parallel coil, but they
> never used a cap on the EOS or flipper switch (that I am aware of).
>

They are, I unwound one to find that out. The primary flip circuit is
in the center and the hold is around it. They have 2 diodes on them as
well.

Now, when williams came up with advertising "parallel wound" coils, they
might have referred to the coils having both the primary and hold coils
being wound in parallel at the core, vs. having all of the flip coil
then the hold coil windings within each other - this would help with
heat dissipation I'd think.

[seymour.shabow]

...although I haven't unwound one of the WMS parallel coils yet

[John Robertson]

The advantage a parallel wound coil has over serial is the game applies
current to both windings at the same time - so both act on the plunger
giving you a bit more power for the same size windings.

An easy way you tell if you have a parallel coil is there are two wires
to an outside lug - the same lug that two diodes terminate. This is the
common for the parallel coils...

A serial coil has the lug with two windings attached as the middle lug.

John :-#)#

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[LexingtonVAPin]

So what physically makes it "parallel". Winding the power coil first
completely across the core?
Then winding the hold on top of the power winding?

In early posts, it was said that the cap on the EOS and flipper switches
reduce the spark only in parallel coils. Did Bally not know this?
Should those games be retrofitted with caps?

What makes the physical configuration of the coil require two diodes?
It seems that the two diodes are really only required when the two
windings are shut off at different times. That occurs depending on how
the EOS is wired to the coil.

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[LexingtonVAPin]

Thanks John. I posted before I saw your reply.

If that is true, then the early Bally coils are serial, not parallel.
But Scott unwound a Bally coil and found it to be parallel.

[I am still not certain what physically determines parallel vs. serial.
I don't have handy old coils to unwind them - I recycled them.]

What keeps a serial coil from being wired to an EOS switch so that 'both
windings are on at the same time'? Will the magnetic fields of the two
windings work against each other?

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[John Robertson]

Parallel means just that - the two fields work together in parallel as
long as they are wound in the same direction.

[LexingtonVAPin]

That makes sense. So if they were both on at the same time, they would
not work together if they are serial. The magnetic field would be weakened.

How can one tell when unwinding it? Would they be wound in opposite
directions? What physically determines if the two coils magnetic fields
would be additive?

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[John Robertson]

It took electronic flipper control to be additive and thus parallel wound.

The whole series/parallel is a bit of a trick. You still have in essence
one large continuous run of wire with a connection.

You could wire the coil with the Power at the centre terminal on older
coils and have the EOS open the power winding and the hold winding would
always be on when the button is pressed. Might work out to slightly more
power - or not. All coils are wound the same direction, so the windings
are parallel...

Series coil

----/\/\/\---|---/\/\/\-|---
|----||----| (EOS)

Parallel coil

----|----/\/\/\---||-|--- (EOS or transistor)
|----/\/\/\------|

That's as good as my ASCII drawing gets...the left connection is the
power (or ground through the flipper switch) and the right lead is
ground through the flipper switch (or power). No diodes 'cause I'm lazy...

Clear?

[LexingtonVAPin]

Great ASCII drawings. Thanks John. Reminds me of my first computer
terminal games.

I wish I had not recycled my burned out coils. I need to do an autopsy
myself on 'parallel' and 'series' coils to see what the difference is in
construction.

Scott said 'The primary flip circuit is in the center and the hold is
around it.'

That is what I imagined the construction parallel coils. Not certain
what the construction is for serial.

Also not certain why two diodes are used on early Bally if the power and
hold windings lose power at the same time. And why not add caps if the
Bally is truly parallel.

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[seymour.shabow]

LexingtonVAPin wrote:
>
> That is what I imagined the construction parallel coils. Not certain
> what the construction is for serial.
>

I should take apart a serial one and see. I assumed perhaps incorrectly
that it was a tap-type situation and the same wire bundle, where the
thicker wire was still in the center and used for the power stroke, then
the thinner wire attaches to that coil's endpoint to add into it for the
hold coil. I dislike ruining good parts even in the name of science though.

> Also not certain why two diodes are used on early Bally if the power and
> hold windings lose power at the same time. And why not add caps if the
> Bally is truly parallel.
>

2 coils collapsing in 2 different endpoints=needs 2 diodes to block
voltage I would assume.

The spark suppression argument I remember from long ago, along with the
Clay video showing the differences and I remember not really noticing any.

[LexingtonVAPin]

On 1/2/21 11:44 AM, seymour.shabow wrote:
>> Also not certain why two diodes are used on early Bally if the power
>> and hold windings lose power at the same time.  And why not add caps
>> if the Bally is truly parallel.
>>
>
> 2 coils collapsing in 2 different endpoints=needs 2 diodes to block
> voltage I would assume.

I think that early Bally and Williams flippers were wired the same way:
EOS switch shorts out the Hold coil. EOS switch opens and both Hold and
Power are energized. Flipper button releases and both coils collapse at
the same time.

One diode should be sufficient, unless there is something about winding
them differently that would require a second diode?

The Bally schematics seem to confirm the EOS Switch shorting out a
(hold) winding. So do early Williams SS. Both drawings make the coil
look like there is a center tap of a transformer.

Marco lists EB flipper coil as 25-500/34-5050.

Bally Strange Science 6803 shows a 0.05 cap on the flipper switch. It
shows a 0.01 cap on the EOS switch. Two diodes on the coil. EOS switch
shorts out a (hold) winding. Marco lists the flipper coil as
24-570/34-3600.

Jumping to a FP2, when Williams upgraded the power supply, they show the
same flipper schematic, with a the EOS switch shorting half the flipper
coil. No cap is present on any of the EOS switches.

Williams HS does not show the presence of a cap on the parts list of the
flipper. The schematic shows a cap on the flipper switch but not the
EOS switch. Schematic indicates EOS switch still shorts out the Hold
winding. Coil looks like a center tap. Coil is 23/600 - 30/2600.

F14 shows a cap on the EOS switch and flipper switch. Flipper schematic
shows a different connection with the EOS switch removing the Power coil
from the circuit. Coils are drawn as two separate coils (no 'center
tap') Hold is always on. Coil is 11630.

I too, don't want to sacrifice a good coil. Would like an early Bally
SS coil, early Williams SS coil and a later Williams WPC era.

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[LexingtonVAPin]

I have been converting an EBD to WPC style flippers. I did this because
I am moving the relatively new linear flippers to a Kings of Steel. And
because I wanted to try doing this.

I don't know if this helps at all but:

Linear flippers - no cap on EOS:

https://youtu.be/78VVc8Vqz-E

WPC style flippers with caps:

https://youtu.be/Q-JN2tVaM0Y

This is the linear upper flipper in EBD. No cap:

https://youtu.be/OuXGx-AH9w4

I added a cap to the existing linear flipper:

https://youtu.be/aID5tXysjUg

This is the same linear flipper, no cap, slow motion:

https://youtu.be/Mj49Eu_dZEk

The same linear flipper, with cap, slow motion. At first, no arcing.
Then after a few flips, arcing occurs:

https://youtu.be/GjwnfehkE8g

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[LexingtonVAPin]

I made an error. The upper left flipper is not linear. It has been
modified to the 05/1975-04/1980 style.

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