(Topic ID: 222803)

Humming sound, WPC-S


By m111111

1 year ago



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  • 16 posts
  • 4 Pinsiders participating
  • Latest reply 1 year ago by m111111
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transformer (resized).jpg

#1 1 year ago

game: #WhoDunnit WPC-S , 1995

There is a humming sound coming from the machine, its not audible at all during gameplay, but in attract mode it makes 10x more sound than my other machines, so i guess something is wrong.

I dont think it is the back-box speakers or the cabinet speaker.
However it feels and sounds like its coming from the WPC transformer.

Any clue what might be the solution for this?

My best
M

#2 1 year ago

I had a JM that did this. I removed a metal cover that surrounded the transformer and it solved it. No ill effects but im sure it was there for some other reason?

#3 1 year ago
Quoted from m111111:

game: #WhoDunnit WPC-S , 1995
There is a humming sound coming from the machine, its not audible at all during gameplay, but in attract mode it makes 10x more sound than my other machines, so i guess something is wrong.
I dont think it is the back-box speakers or the cabinet speaker.
However it feels and sounds like its coming from the WPC transformer.
Any clue what might be the solution for this?
My best
M

Likely the transformer. It's called "singing". There are fixes out there for it that involve rubber mallets and smacking.

https://pinside.com/pinball/forum/topic/king-of-diamonds-transformer-buzzing-loudly

2 weeks later
#4 1 year ago

Thanx guys, gonna try the rubber mallet smacking thing first

#5 1 year ago

Hmm... tried the following:

Switched machine off.

Unplugged it from the wall.

Smacked transformer hard a bunch of times with rubber mallet.

Turned machine on, but "singing" still present.

I have done this maybe 5 times now.

Look at attached image, i am only able to smack it hard enough on the upper side.

Am i smacking it "wrong"?

Might it be something else?

transformer (resized).jpg
#6 1 year ago
Quoted from m111111:

Hmm... tried the following:
Switched machine off.
Unplugged it from the wall.
Smacked transformer hard a bunch of times with rubber mallet.
Turned machine on, but "singing" still present.
I have done this maybe 5 times now.
Look at attached image, i am only able to smack it hard enough on the upper side.
Am i smacking it "wrong"?
Might it be something else?
[quoted image]

Oh, you have a foreign one. Dur. I forgot, those are mounted sideways.

You need to smack from the TOP, which is the side for foreign cabs. I don't think it will work if it's mounted sideways. You'll likely have to remove and rotate it into "USA position" then smack from there. You can probably leave it loose in the cabinet, smack and re-test, then re-mount it when you have it quieted down.

#7 1 year ago

Yes, that probably explains it, i was just now noticing that on my TZ, the transformer was oriented different, with the "USA angle".

Ok i will try remove it and smack away.

Btw, is there any risk for me handling the transformer ? Is it carrying a residue charge? ( after unplugged from the wall ofcourse ).
Thanx Vireland

#8 1 year ago

That looks like my one. I removed that big silver plate behind the transformer like i previously mentioned.

#9 1 year ago
Quoted from m111111:

Yes, that probably explains it, i was just now noticing that on my TZ, the transformer was oriented different, with the "USA angle".
Ok i will try remove it and smack away.
Btw, is there any risk for me handling the transformer ? Is it carrying a residue charge? ( after unplugged from the wall ofcourse ).
Thanx Vireland

As long as you're unplugged from the wall, you should be fine in my experience. I don't think transformers store energy like capacitors (if someone else knows differently, please chime in and save a Norweigian getting shocked).

#10 1 year ago

So i unmounted the transformer, smacked it again, but it was still "singing".

Then i removed the metal cover, and.. "singing" gone.

Anyone know what that metal cover is for?
Might it be to evenly distribute ground along from the ground-wire visible in the image above?
Is there a risk to remove it ?

Will it be enough to have the ground touch the one side of the transformer as visible in the image? The ground would then still be between the metal foot and the wood.

#11 1 year ago
Quoted from m111111:

So i unmounted the transformer, smacked it again, but it was still "singing".
Then i removed the metal cover, and.. "singing" gone.
Anyone know what that metal cover is for?
Might it be to evenly distribute ground along from the ground-wire visible in the image above?
Is there a risk to remove it ?
Will it be enough to have the ground touch the one side of the transformer as visible in the image? The ground would then still be between the metal foot and the wood.

Probably just for fire-protection so it's not mounted to wood. Maybe a European regulation thing because the USA ones are mounted straight to the wood in the bottom center of the cab - no metal plate.

#12 1 year ago

Agreed.

But, on a sidenote:
On my TZ and my STTNG the transformer actually is mounted on wood in the bottom, center of cab.
There is however a second layer of wood there, with space between.
Is this layer ment for mounting of the transformer alone?
Would there be any logical reason the transformer should not be mounted on the cabinet-wood directly?

#13 1 year ago
Quoted from m111111:

Would there be any logical reason the transformer should not be mounted on the cabinet-wood directly?

My best guess...
Without the metal shield the electro-magnetic lines of flux from the transformer may be capable of extending beyond the cabinet and cause interference to external devices by inducing noise on power cables behind the machine, this type of external interference is not allowed; the shield may have been required in order to prevent this.

#14 1 year ago

Why do transformers hum?
Transformer noise is caused by a phenomenon which causes a piece of magnetic sheet steel to extend itself when magnetized. When the magnetization is taken away, it goes back to its original condition. This phenomenon is scientifically referred to as magnetostriction. A transformer is magnetically excited by an alternating voltage and current so that it becomes extended and contracted twice during a full cycle of magnetization.

The magnetization of any given point on the sheet varies, so the extension and contraction is not uniform. A transformer core is made from many sheets of special steel to reduce losses and moderate the ensuing heating effect. The extensions and contractions are taking place erratically all over a sheet and each sheet is behaving erratically with respect to its neighbor, so you can see what a moving, writhing construction it is when excited. These extensions are miniscule proportionally and therefore not normally visible to the naked eye. However, they are sufficient to cause a vibration, and consequently noise. Applying voltage to a transformer produces a magnetic flux, or magnetic lines of force in the core. The degree of flux determines the amount of magnetostriction and hence, the noise level.

Why not reduce the noise in the core by reducing the amount of flux? Transformer voltages are fixed by system requirements. The ratio of these voltages to the number of turns in the winding determines the amount of magnetization. This ratio of voltage to turns is determined mainly for economical soundness. Therefore the amount of flux at the normal voltage is fixed. This also fixes the level of noise and vibration. Also, increasing (or decreasing) magnetization does not affect the magnetostriction equivalently. In technical terms the relationship is not linear.

Source: https://www.mgmtransformer.com

#15 1 year ago
Quoted from vireland:

Likely the transformer. It's called "singing". There are fixes out there for it that involve rubber mallets and smacking.

Why does this work? The physics involved here deal with attempting to remove the magnetism that the transformer has picked up over the years...

https://sciencing.com/demagnetize-magnet-5071154.html

#16 1 year ago

Yes, but in my case what worked was to remove the metalcover, or am i wrong?
The tiny vibrations between transformer and the cover was the singing, not the transformer itself.

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