Any video? I always hated how wimpy the Gottlieb knockers sounded compared to my Bally solid state games.

I feel just the opposite and put a felt chair leg pad on TAF to keep the knock a bit more subdued. Even with that in a friend who played jumped when the knock happened.
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Modern solid state games have always had loud knockers, since the coils are rectified, and the plunger thwacks against the actual cabinet--making for a huge resonating chamber effect. The OP is referring to knockers that are used in EMs. They're always really lackluster since the coil isn't DC powered, and they only strike a metal plate that the coil is attached to. Williams was always the worst offender though, since the coils were weak, and mounted towards the rear of the cabinet.

I'm with you! And I'll definitely follow your example!

No.

That's the type of knocker that is in the Acrylic Pin. (Sonic with Williams guts.) It makes a stupid little barely audible sound. I wanted to turn it 90 degrees so it would thwack the case like a Bally but I am afraid of cracking it. This might be a better solution.

Shawn

Where did you order the knocker from? How much $ ??

This is a great thread with good ideas. I have a question as a new Pinsider: I recently bought a 2016 Stern Whoa Nellie machine and it has a mechanical knocker installed. How do I set it to go off during game play? It's currently set to free play with extra credit or replay, not extra ball. I lowered the score threshold but still the knocker does not go off. It tests fine though. Any ideas to get it knocking?

anyone know of a way to retro fit EMs and Williams games with the Stern knocker chirp?

just kidding. nobody on earth likes that noise.

In my EM I have the Bally "Sounder Assembly" with adjusting screw and I can hardly hear it over the machines normal noise. Would love to make it louder - what is the gizmo being used across the lugs? Thanks.

Edit. Found it, KBL01 bridge rectifier, I haven't seen that casing type before, thanks

The more I look at it, how necessary would it truly be to even slap that extra diode across the lugs? Considering a bridge rectifier is just 4 diodes, assuming the bridge you have on there is beefy enough, I can't imagine you'd need the snuffer diode.

This made me wonder if it would be possible to put a knocker on a modern Stern pin and disable the electronic chirp? If someone made a mod to do that I bet it would sell well.

Someone here on site has made this for newer SAM systems and easy parts from Pinball Life. Yes if Stern sold a easy plug in kit like a shaker system with wiring and board it would be a great seller for those of us that love that loud crack on replay or match.

I have always preferred big knockers over loud knockers

Before doing such mods:

For Gottliebs, I centered the knocker assembly as close to the side of the cabinet as possible,
(it seems to help), then replace the original coil with a pop-bumper coil, (4893). Make sure the
assembly is mounted firmly against the cabinet, (any play will muffle the sound), The stronger
coil will have it banging like Saturday Night! It may compromise the life of the plastic plunger
tip a bit, but in the home setting, not really.

I've always been happy with the knocker on my Wms Games and never did anything other than
firmly tightening the mounting screws to the cabinet, but if not satisfied, I'd try the same,
(replacing with a pop-bumper coil), before getting into more complicated mods.

The diode is absolutely needed in this modification. It prevents the backflow current, when the coil magnetism collapses, to extend the life of the bridge rectifier. since there's no fuse in this modification (a bad idea if the bridge shorts!), you better damn well have that diode in place! Speaking of which, there really should be a fuse in this modification. Technically two fuses, one on the AC input and another on the DC output sides. But even one (DC side) would be appropriate. I guess the worse thing to happen is that coil does a total meltdown. Usually coils don't start on fire, so i guess you're OK here...

Note that williams made a mistake in their mid to late 70s EMs and did not use a diode on all the DC coils. Bally (and in 1978) Gottlieb did. I guess that's why i've only had to replace bridges on Williams EMs (and never on a Bally).

Really appreciate you clearing up the diode question and adding fuse. TY. Now I will try this mod and see what happens.
-Mike

bwaaahahhaaaaa, this is what I was thinking the entire time I was reading this thread. all this talk of knockers... I love all shapes and sizes of knockers... I also love loud knockers and quiet knockers too, they just aren't as much fun... thanks @gac, made my morning!

Shame a fuse is recommended on the DC side as installing the BR and diode straight across the lugs is a neat idea.

I have a KBL406 BR on order, I'm going to croc clip it together to gauge the improvement before doing a proper install. Will report back.

There's already a fuse for the whole AC circuit so there's no particular need to add any fuses at all, unless you want a lower amp rating than the existing fuse.

Well that's what Williams thought too on system3-11a games. But i can't tell you how many of these machines i've seen with melted wiring harness and near-fires because of the lack of a fuse on the AC side of the lamp and coil bridges. It's always a good idea to have fuse(s). Williams went one step further on sys11b, and added a fuse to both AC inputs to their bridges because of this problem (though that is probably overkill.)

If there's cloth wire involved (because it's an EM), fire is particularly a potential issue. Cloth insulated wire does not melt, it burns. On the other hand, it is just a knocker coil. So yea, no one is going to die without fuse(s). But there is a reason williams added them. It's kind of a roll of the dice, but the odds are in favor of no issues.

The picture for this mod was completely adequate to perform the mod which I did. Very happy with the results!

Also clean any oil or grime off the plunger so it moves smoothly. You can feel the CRACK in your right hand too now!

"What knockers"!
"Why, thank you doctor".

Can someone explain to me the theory why this knocker is louder than the original? Something to do with DC vs AC? Thanks.

Here is what Tim Arnold had to say about this:

"35 - NICE KNOCKERS
As a kid I lived for the sound of the free play knocker! But now, when I get a game in, it isn't as loud as I remembered! What has happened, the knocker is no longer being held tightly to the side of the cabinet! Tighten the screws, or even better yet bolt it thru! Lop of 20% of the wire (See #24 and #30) and it sounds like Detroit on a Saturday night! "

https://tuukan.fliput.net/tim_en.html

Personally, I've always been OK with what I had.

This is using an elephant gun to kill a fly.

Still doesn't explain to me why DC vs AC for louder knocker. I think I get what Tim Arnold is saying...make sure the assembly is tight to the cabinet, and remove 20% of the windings so the coil acts stronger, right? But the OP says convert to DC. That part I don't understand the theory. Is it because the full wave rectified voltage is higher than the AC RMS voltage and therefore produces stronger coil energy?

Yes.

The extra diode is not necessary indeed. The bridge rectifier itself consists of 4 diodes which do the job. You could replace the diode by a capacitor of 1000 MRD (mind the polarity). It will make the knocker even stronger.

Great! Thanks for satisfying my knocker curiosities.

my knocker curiosity is never satisfied, always looking for more.

I'm not convinced that this is what's going on. Unmodified, the AC voltage fed into a knocker, or any other solenoid, crosses 0 volts and looks like this:
AC Voltage (resized).jpg
When you throw a rectifier in there, the rectified AC voltage to the solenoid no longer crosses 0 volts and looks instead like this:
Rectified Voltage (resized).jpg
Note that the rectified AC voltage will actually be slightly lower than the AC voltage because of the voltage drop (~.7 volts) across the diode in the rectifier, but let's ignore that for now. Typically when AC voltage is rectified a capacitor is used to smooth out the voltage like this:
Smoothed Rectified Voltage (resized).jpg
The green part of the graph represents the voltage that the capacitor supplies to the solenoid while the rectified AC voltage dips to zero and back. The capacitor is usually recharged with each voltage peak so the average voltage is higher with a capacitor than without one. So with a capacitor on the output of the rectifier it's easy to see why a knocker would be stronger using DC (or smoothed, rectified AC) than plain old AC. There's just more voltage more of the time.

But the mod suggested here doesn't use a capacitor so something else must be going on. The strength of the knocker is determined by the magnetic field created in the solenoid. The magnetic field is proportional to the current flowing through the solenoid. Since it's the amount of current and not the direction of the current that determines the strength of the magnetic field the current represented in the first two graphs above is the same. If the knocker is really stronger with a rectifier there must be something else that's increasing the magnetic field in the solenoid when going from AC to rectified AC.

I think what's going on is that the knocker (which is an inductor) is conserving energy between voltage peaks much like the capacitor does in the third graph. When using AC, the voltage across the knocker changes polarity (from positive to negative to positive) each cycle so the current must also change direction. But like capacitors resist changing voltage (as shown in the third graph) inductors resist changing current. Changing current from one direction to the other (AC) takes a lot more energy than reducing and increasing the current in the same direction (rectified AC). So what may be happening is that with rectified AC, the knocker solenoid is putting more energy into moving the plunger and less energy into changing the current than it does with simple AC. That's probably why the knocker is stronger with a rectifier. Note that it would probably be even stronger with an capacitor added to the rectifier.

/Mark

I played a Bally "Freedom" and the knocker was so loud! The owner told me he took off the rear plate and that was why it was so loud.

The 50 volt knocker that came stock in my 1960 Williams Magic Clock is louder than the modern games I own.

I guess when the entire cabinet including the bottom is made with thick plywood and you run 50 volts in an EM you don't need any modifications. They had it right in the first place.

Knockers come in all shapes and sizes, right? Well have a look at mine and tell me if it looks normal. It is in my 1966 Bally Bazaar, showing in the power off position. When it knocks the plunger moves down only about 1/4" into the coil before it stops then returns to the upper position. It's not loud. None of my other knockers look/work like this. Oh, and I've unscrewed that brass stop and that doesn't help. Comments? Help?

IMG_8190 (resized).jpg

It's normal.
Bally Sounder Assembly (resized).jpg
The spring inside the plunger may have weakened over time though, or your air gap might not be right.

/Mark

Those older Bally knockers are barely audible. It's just how they are I guess.
They sure made up for it when they started SS games!

This is indeed a common knocker. Bally used this type of knocker in EM games for many years. This model produces a gentle, double 'click' and is typically weaker than the Williams models.

So I have an all original 1966 game, Bazaar, with this "gentle" knocker. Would it be a sin to replace it with a newer style that wakes up the dead? I mean, I get a thrill when I hear a loud knock....like I really won something. Or should I just accept it as the way it was back in 1966?

You mean you want to subject your "Bazaar" to a knocker enhancement procedure?

If you replace the coil, you'll want to use another 50 volt coil
https://www.ipdb.org/files/201/Bally_1966_Bazaar_Schematic_Diagram_continuous.pdf

Not my quote. How did that happen?

Must be a bug but I was able to fix it.

Thanks, Howard.

If you run the screw up higher in the Bally Bazaar knocker, it will become louder. Bally knockers just have a different sound than the others. They have more of a click sound than the usual knock sound.

The loudest knocker in my collection belongs to my Williams Ding Dong. When I bought the game, someone had removed the knocker so I replaced it with a Gottlieb knocker from PBR. It has to be the location of the knocker, back in the back left corner, and composition of the cabinet because this thing is way louder than my other Gottlieb knockers. It literally sounds like a hammer coming down on something. Whack!

Yeah, Iv'e run the screw all the way up. Still not too loud, but I guess it's ok in my home environment. If it was in an arcade you wouldn't hear it. All Bally knockers are not like that. For example, my Hokus Pokus is LOUD! My Old Chicago is LOUD! I've been playing Bazaar every day. I'm getting used to the click-click sound.