(Topic ID: 253200)

"White Noise" Coming from Right Speaker?

By jimgravina

4 years ago


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  • 15 posts
  • 3 Pinsiders participating
  • Latest reply 4 years ago by wayout440
  • Topic is favorited by 1 Pinsider

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#1 4 years ago

Recently finished recapping my Data East sound board and power board in hopes to combat the hum/buzz many DE games have. This did not work, however, wiring in an aux power supply to power the sound board solved the issue.

Now, I still have a slight buzz from the transformer, but it is no longer filtering through the speakers. However, I still have a buzz during attract mode when the lights are dancing around (which i do not think there is a solution for yet), and I am also getting some noticeable "white noise" coming from the right speaker.

It is not a "hum" or a "buzz" but more like a white noise as if your not directly tuned into a radio station. I am not sure if this has always been there, and am just now noticing now that the main buzz noise is gone, or if this is a new issue.

Could this be a bad capacitor solder? I'm definitely not the best at it so its very possible...any other ideas what could cause this white noise?

Thanks,
Jim

#2 4 years ago
Quoted from jimgravina:

Recently finished recapping my Data East sound board and power board in hopes to combat the hum/buzz many DE games have. This did not work, however, wiring in an aux power supply to power the sound board solved the issue.
Now, I still have a slight buzz from the transformer, but it is no longer filtering through the speakers. However, I still have a buzz during attract mode when the lights are dancing around (which i do not think there is a solution for yet), and I am also getting some noticeable "white noise" coming from the right speaker.
It is not a "hum" or a "buzz" but more like a white noise as if your not directly tuned into a radio station. I am not sure if this has always been there, and am just now noticing now that the main buzz noise is gone, or if this is a new issue.
Could this be a bad capacitor solder? I'm definitely not the best at it so its very possible...any other ideas what could cause this white noise?
Thanks,
Jim

It could be a lot of things. Check DC offset at the amplifier for that particular channel, use an oscilloscope to examine the audio waveform somewhere in the final amplification stage, see if the noise is there, then move upstream or downstream to isolate where it originates.

#3 4 years ago
Quoted from wayout440:

It could be a lot of things. Check DC offset at the amplifier for that particular channel, use an oscilloscope to examine the audio waveform somewhere in the final amplification stage, see if the noise is there, then move upstream or downstream to isolate where it originates.

I'll have to get a buddy to help with that...a bit out of my capabilities. But good place to start! Thanks! It's not super annoying, but its noticeable when game is in attract mode.
Jim

#4 4 years ago

Another possibility that is often overlooked is your boards in the back box not utilizing enough or all of the screws to hold them in place against the grounded frame. The frame is not used in the sense of the boards needing the ground to properly run. Its utilized to give the boards a common ground with the sound board which helps reduce or eliminate hum.

Loose grounds throughout the machine can cause issues with interference.

Also if your PS is not properly grounded this can become an issue. In Vids if the video pattern is "herringbone" or has "worm wiggle" as some folks refer to it, then you need to wire a jumper between the FG terminal and the DC ground terminal of your PS.

Thanks
Blake

#5 4 years ago
Quoted from Blake:

Another possibility that is often overlooked is your boards in the back box not utilizing enough or all of the screws to hold them in place against the grounded frame. The frame is not used in the sense of the boards needing the ground to properly run. Its utilized to give the boards a common ground with the sound board which helps reduce or eliminate hum.
Loose grounds throughout the machine can cause issues with interference.
Also if your PS is not properly grounded this can become an issue. In Vids if the video pattern is "herringbone" or has "worm wiggle" as some folks refer to it, then you need to wire a jumper between the FG terminal and the DC ground terminal of your PS.
Thanks
Blake

Yeah, I have checked all the main culprits. Everything is tight and secure...will double check the ground on the PS though...I have an alpha numeric display so I can't use that test to judge it. I did just hook in an aux PS to power the sound board, and maybe the white noise is coming form the new PS? I do have another PS laying around I can use to test....

#6 4 years ago
Quoted from jimgravina:

Yeah, I have checked all the main culprits. Everything is tight and secure...will double check the ground on the PS though...I have an alpha numeric display so I can't use that test to judge it. I did just hook in an aux PS to power the sound board, and maybe the white noise is coming form the new PS? I do have another PS laying around I can use to test....

Is that new power supply tied into the common ground?

Thanks
Blake

#7 4 years ago

I am a little new at this (but have done alot of research) and my setup is as follows with pictures to explain.

The incoming AC wires into the aux power supply, which then feeds into the transformer. The outgoing DC power of the aux PS (+12, -12, +5) feeds the sound board. The COM connection on the aux PS feeds the GND pin on the sound board.

I will say that the aux PS does have a FG connection that I am not using (I was told using the COM would be ok). The black wire in this case is the ground wire and also included a pic of the outputs of the aux PS.

Do I need to move the ground wire to the actual FG ground on the PS? I also included a pic of the PS data sheet...thank you so much for the help!

Jim

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#8 4 years ago
Quoted from jimgravina:

Do I need to move the ground wire to the actual FG ground on the PS?

No this is specifically for the example I gave about vids/monitors and was simply reinforcing the theory of interference associated with ground. If ever doing this you want to be sure your chassis and cab wiring are all correct (someone hasn't swapped the hot/neutral) or it could be fireworks.

What I wonder is why if you have a PS that has FG as an input terminal and your pulling your A/C line and A/C neutral from the transformer, why is there not a FG from the cabinet of the pinball machine connected? This would be normal wiring procedure for any switch mode PS receiving its power from an A/C source.

I could be wrong and maybe your PS manual specifies why, but from my understanding there should be a common ground connecting all the metal pieces in your cabinet. Especially switch mode power supplies as they can produce a lot of feedback. I am guessing that one post of the transformer there is a ground. And that ground has continuity with the coin door, side rails, ground braid, fuse assembly, line filter exc.

Thanks
Blake

#9 4 years ago

This is exactly why i come to this forum as I am not entirely sure. I was just following another PINSIDE thread regarding this setup...

To answer your questions, I do have a ground braid running through my entire machine, and as far as i know, everything is connected to it correctly. As for the aux PS, Im not powering it from the transformer, im powering it from the AC line right after the switch...then powering the transformer.

As for the PS ground...I was just following what someone else has suggested. Are you saying I should consider connecting the Power Supply Floating ground to the ground braid?

#10 4 years ago

Also make sure that your grounds (usually green or green/yellow) are somehow tied into the ground on your A/C line filter. Usually they will be attached to one of the mounting screws. If you don't see this then you could have all sorts of interference.

thanks
Blake

#11 4 years ago
Quoted from jimgravina:

As for the aux PS, Im not powering it from the transformer, im powering it from the AC line right after the switch...then powering the transformer.
As for the PS ground...I was just following what someone else has suggested. Are you saying I should consider connecting the Power Supply Floating ground to the ground braid?

I would first try and locate the manual for the PS you are using as that may provide valuable insight on how to wire to a specific scenario.

The standard input wiring for a switch mode PS is A/C line(hot) and A/C neutral, then FG. FG in this scenario can be traced back all the way to the ground plug of your power cord.

I have to go pick up my son for soccer practice so I don't have time right now to get you a good diagram. But if you look up on google "how to wire a switch mode PS" I am sure there are tons of diagrams and tutorials.

But look up your manual first. Maybe you don't need it in your case. I will touch base later on.

Thanks
Blake

#12 4 years ago

All the things Blake has suggested affect ALL channels, not one. If you are having the noise on all channels (L R backbox and cabinet) then by all means investigate those suggestions. As I interpreted your post, you had the problem on ONE of the three audio channels, which is a very localized final auidio amp problem to the sound board.

#13 4 years ago
Quoted from wayout440:

All the things Blake has suggested affect ALL channels, not one. If you are having the noise on all channels (L R backbox and cabinet) then by all means investigate those suggestions. As I interpreted your post, you had the problem on ONE of the three audio channels, which is a very localized final auidio amp problem to the sound board.

Correct, I am just hearing the "white noise" mainly in the RIGHT speaker. It exists in the left, but very very faint. I would say I heard 90% of it in the right, 10% in the left.

#14 4 years ago

I apologize, it does seem like the white noise is coming from all 3 speakers (though louder on the right).

I will look Further into grounding the aux power supply.

#15 4 years ago
Quoted from jimgravina:

This is exactly why i come to this forum as I am not entirely sure. I was just following another PINSIDE thread regarding this setup...
To answer your questions, I do have a ground braid running through my entire machine, and as far as i know, everything is connected to it correctly. As for the aux PS, Im not powering it from the transformer, im powering it from the AC line right after the switch...then powering the transformer.
As for the PS ground...I was just following what someone else has suggested. Are you saying I should consider connecting the Power Supply Floating ground to the ground braid?

Earth ground is the 3rd terminal pin on that supply marked with the earth ground symbol. You should have your AC ground connected there, from the middle pin of your 3 pin AC mains plug. This terminal should then have continuity with the AC mains middle pin, braid, and external metal parts of the game (coin door, side rails etc...) If you have a metal chassis, then it's pretty much required to at least ground that in case a live wire comes loose inside and hits the case, for example. Then it trips a breaker / blows a fuse and shuts off instead of frying someone.

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