Could always just disconnect the chimes and bells for now.

By cloth trick, do you mean putting an entire hand towel on top of the chimes?

A resistor would need very high wattage. A cushion or other thick padded covering is best. you could also try covering the chime box so the sound has no echo.

The chime coil gets quite short pulses, so something like 10 ohm/5 watt resistor could work. But I also think putting some kind of cushioning between plunger and chime bar would be the best solution. Some adhesive felt pads or foam rubber maybe?

With a resistor, there always possibility that the plunger does not hit the chime bar. It is designed so that when activated, the plunger "overshoots" striking the chime and then returning back slightly. Otherwise, if the plunger when energized keeps touching the chime, it would dampen the sound. With a resistor, the overshoot might not happen and plungers just jump up and down without ever reaching the chimes.

Have you contemplated a My Pillow for sound suppression ?pasted_image (resized).png

But seriously folks, Mike Lindell looks great in blue.

I own a My Pillow. Best damn $40 pillow on the market.

If you prefer not to mess with the chime unit so the sound is unaltered maybe you could surround it totally/partially with an open ended box lined with foam or whatever, to just reduce the volume... that is if you have room to put it around the unit where the open end is against the side of the cabinet. Sounds like a lot of trouble though. Would be great for the loud-as-hell ringer on BK though, I imagine trying to quiet that would make it sound lousy. Maybe isolate that one from the cabinet by putting a rubber bushing where it mounts, I think it's screwed directly to the cabinet.

I often need to quiet a mechanical pump to prevent interference with acoustically sensitive lab equipment. The solution is placing an enclosure over it, made with some light MDF and lined with sound deadening material. (In the case of the pump, they also put out a LOT of heat so a vent and small fan must be added, but not necessary in this case.)

You can buy inexpensive sound deadening material with adhesive backing to make one. Also, the chime box is bolted to the bottom of the cab, so that must carry some of the initial strike sound, so a rubber mat under the box would help.

Try placing a cardboard box over the chimebox to get the idea what I'm talking about.

While you're experimenting, try to determine what factors make the sounds louder or quieter.
If you strike with a lighter object at the same speed does the volume change?
If you change the size of the striking area does the volume change?
If you strike faster does the volume change?

You might think of other possible solutions if your experiments turn up something unexpected.

Cardboard box. I like that idea. My Pillow is sold in a cardboard box.Neal_ W is on the right track
pasted_image (resized).png

How about clamping something, like a small block of wood or several rubber-tipped clamps, to the chime bars or bell?

How about this one - raising the chime bar grommets in tiny increments in their mounts, enough so that by the time the plunger hits it, it has slowed down a little more before it hits the chime and so will be quieter but with same impact sound? Like dialing that in until the plunger hit and the ring are quieter but it's not missing any 'hits' because it was raised a little too high. No idea if or how good it might work, just tossing it out there.

The main sound that is going to travel is all the solenoids hitting their coil stops. There's no way to block this and still play the game. You may not hear this as the "pinball" sound, but people in other rooms do, and that's all they hear.

Seems like insulating the whole chime unit from where it's mounted would blunt it a little or a lot depending on how was done. I'd think just the plunger falling back on its coil stop would be barely audible with the door closed if the unit was mounted so there's a good deadener between it and the cabinet. I dunno like felt, or insulating it with rubber grommets at the mount holes, so the unit is only contacting the grommets.

I'm not referring to just the chime unit - I mean all the mechanisms in the machine, that's where the noise is coming from that travels between walls.

1 Record the sounds of the chimes and make them into MP3s.
2 Disconnect the chimes.
3 Install a MP3 trigger sound board with a speaker and a volume control.

Problem solved

Doesn't matter where you put the resistor it's going to resist either way.

https://www.easycalculation.com/physics/classical-physics/voltage-drop-across-resistor.php

http://www.ohmslawcalculator.com/ohms-law-calculator
You can see what effect increasing the resistance will have on the current.
V=I*R is the basic form of Ohm’s Law. Dividing both sides by I gives you V/I=R

Looking at a graph may help you understand the relationship. https://ohmlaw.com/how-slope-of-a-voltage-current-graph-relates-to-resistance/

V=IR will get you a long way!!

As to which way the current flows (DC), well that's a topic of long debate. But in the end it doesn't matter, pick a direction and design around it. The key is that it is going one way, as opposed to back and forth 2 ways like AC. Most of the time when we look at DC circuits we thing about it as going from positive to negative, as per convention that goes back a long time. But its actually going from negative to positive. Probably.

Resistors don't have any +/- orientation, they work the same in either orientation. Capacitors, diodes, and some other stuff, not so much.

There is a ton of cool stuff out there to learn about circuits. The books by Platt are very good I think. Such as Make Electronics 2nd edition

https://www.amazon.com/Make-Electronics-Learning-Through-Discovery/dp/1680450263

There are plenty of others.

In a pinch to get a game working I have put a low ohm power resistor in series with a stronger coil. BSD kickout to left inlane. Worked fine and have left it that way for a few years now.

I had to tinker with the value to get it the strength i wanted. I think i ended up with a few 3w of equal value resistors in parallel.

In parallel is the key. Splitting the load between several resistors in this application. BTW https://nvram.weebly.com/ is barakandl ’s site. If you need what he has buy with confidence.

Been watching this thread, interested if this resistor theory will work.
I don’t think you can get the coil weak enough to make a big difference in the sound without the coil being so weak it can’t draw the plunger up from rest.
That made me think that in addition to weakening the coil, I would shim the plungers to have a lot less travel, and that made me think that alone might do what you are trying.
Have you tried just shimming the plunger to only have like 1/2” of travel?
That alone might work.

A resistor can be used but it isn't pretty.
If you know the coil voltage and and the coil resistance then you can determine how much current travels through the coil and how much power it is dissipating while energized.

Using round values for an example: 48V source and a 4 ohm coil -- you have (48V / 4 ohms) or 12 amps.
During the on period - the coil is dissipating (48V * 12A) = 576 watts. That puppy is going to get hot if locked on!

Adding a series resistor will lower the voltage drop across the coil which will reduce the current flow and the power dissipated (and physical power transferred to chime).

Suppose you add a 1 ohm (pretty high value) resistor in series with coil:
(48 volts / (4 ohms + 1 ohm)) = 9.6 amps. You have reduced the coil current and power to 80%.
Power dissipated by both coil and resistor = (48V * 9.6A) = 460 watts. A lot less but still quite a bit.
Power dissipated by coil only = ((9.6A * 9.6A) * 4 ohms) = 368 watts.
Power dissipated by resistor only = (9.6A * 9.6A) * 1 ohm) = 92 watts.
In a locked on coil - it will be a race to see which burns up first - the coil or the resistor (assuming the fuse doesn't blow first).
Theoretically, for the resistor to survive and everything else still burn up - you need a 200W resistor (don't go above 50% rated power).

Thankfully, coils don't lock on very often and are protected by fuses when they do.
The actual wattage of resistor you need depends on how often the coil is pulsed and for how long.
As long as the resistor is allowed to cool between activation cycles then you're covered.

The hard part is figuring out the wattage value for the resistor required for these pulse overloads. There have been studies done on most resistor types for pulse overloads but I have never read them so can't go any further on that one.

Many resistors have a pulse overload test performed by manufacturer. This pulse overload test is typically performed at 4x rated power and typically at 1 second on, 25 seconds off. Coils are typically on for only milliseconds at a time with more than 25x inactive gaps between. My seat of pants guess would be that a 20W part (still a whopping 10x pulse overload) would work in a properly working circuit. Locked coil and all bets are off. I would love to see how many pieces a quarter watt carbon film resistor would burst into if this was tried.

Resistor clump is about 4.8 ohm and the coil resistance is 4 ohm for total resistance of 8.8 ohm.

No evidence the resistors have been overheated.

I actually did buy the right coil just never got around to proper fix since it works fine.
20200403_211206 (resized).jpg

Stern Meteor and Stern Seawitch had a power resistor in series with a flipper coil. Probably because an upper flipper so close to drop targets they where getting busted. I can't remember the value Stern used, but it might be included in a wiring diagram.

My Lightning manual says for games with extra flippers sometimes a 1 ohm 5 watt resistor is used to reduce power.

There are multiple resistors of equal value (looks like each resistor is a 27R 3w) parallel to each other. But the resistor clump is in series with the coil.

Here is a nice online calculator tool that you can use to help figure out parallel resistor values. And to think, I used to do this manually in college!

http://www.sengpielaudio.com/calculator-paralresist.htm

The resistors look like 27 ohms to me also (Red-Violet-Black). However I think there are at least 4 of them, and probably 5. It looks like 5 total wires in each clump. You can see one partially hidden behind the front 3. They are wired in parallel which would make their total resistive value nominally 5.4 ohms which is somewhat close to the stated measurement of 4.8 ohms. (assuming 5 resistors, since they are in parallel and all the same value, then the total resistances is 27 divided by 5).

The dissipation of the wattage load isn't directly affected the the parallel resistors. Its the total resistance in the circuit that determines this, along with the current. Total resistance was stated to be 8.8 ohms.

That old standby V=IR always works. Or if you rework it you could say I=V/R. If the voltage is 48V then the current I is about 5.5 amps (divide 48 by 8.8).

The other handy equation is P=IV if you want to know the power (wattage). In this case it is 5.5 x 48 = 264 watts.

If you want to get fancy you can also calculate the power as V squared over R. That would be (48x48) / 8.8 = 262 watts. The minor difference is due to some rounding I did.

Based on all this, as as typical in pinball, this is not a circuit you would leave on for any length of time. The resistors would not handle the power. That is also why typical coils burn out if they are locked on. It is meant to be a transitory circuit. That's why coils that are on most of the time like a Lock relay have a much higher resistance (like 100 ohms), to cut the current down and therefore the power.

Assuming I got everything correct, I am not an electronic engineer, I just play one on the internet.