(Topic ID: 272019)

How to shield the audio board?


By bghill

12 days ago



Topic Stats

  • 3 posts
  • 2 Pinsiders participating
  • Latest reply 8 days ago by bghill
  • Topic is favorited by 1 Pinsider

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#1 12 days ago

The player four 7-digit display is inducing noise in my audio card. In attract mode, it causes a buzz each time the display flashes. Can I build a shield to prevent this? What have others done for this kind of problem?

Background:
The machine is a Bally's Fireball Classic. I've been trying to improve the sound. It works, but there is far more noise than I would like. On machine startup, there is a period of static before any sound starts. Then I get the startup sound. Then in attract mode, I get buzzing as the digit displays flash. I started by replacing the audio caps (C4, C29, C30) on the Cheap Squeak, hoping that is was a frequency filtering issue. No dice. Then I noticed the sound went away when I swung the display open. The sound clearly seems to be a function of how close the player four 7 digit display is to the audio board. I presume the digit display is inducing the static.

#2 8 days ago

Perhaps using a choke or ferrite core on the wires feeding the 4th display might reduce some of the noise. Have heard sounds like this on many games before and it's probably normal.

Haven't personally ever done this, but it's whats normally done to reduce noise. Not sure if you would have to desolder all the wires feeding the display and wrap them around the choke or not. That would be a huge effort though.

#3 8 days ago

I hadn't thought of that. Amazon seems to have relatively inexpensive ferrite choke rings. Most are snap-on, so I shouldn't have to desolder and re-attach the connectors. I'll dive into researching this to see if it would work.

Thanks!

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