sand1
Active member
Hi all!
I believe I narrowed down what causes the "Nintendo hum" and how to fix it.
I recently picked up a Donkey Kong and a Punch-out. The hum produced by DK was annoying and the PO hum was obnoxious.
After reading though dozens of Nintendo hum related threads I found lots of possible solutions mostly relating to rebuilding the 20ez audio amp or recapping the game's power supply. Most people reported these solutions did not work for them. Others reported using a separate 12v sound amp and some said they designed their own amps for Nintendo games. While others simply stated "that's what Nintendo game do".
I tried the following ...
* Recapped the power supply (didn't help)
* Rebuilt the 20ez audio amp (didn't help)
* Rebuilt the 20ez rectifier circuit (didn't help)
* Put a 430uf cap across the speaker output (this filtered out most of the hum but also made the game sound like you were playing it underwater)
Then I found the last post of this thread...
https://forums.arcade-museum.com/showthread.php?p=3014160#post3014160
The post above suggested unplugging connector JB, moving C379 to the "correct" position and installing a 50k pot at VR371. This made sense as the wire going from connector JB to the adjustment pot board utilized the only shielded cable in the entire cabinet. Eliminating this cable entirely might help. So I ordered a few of these pots http://www.digikey.com/short/3912b7
To be clear, you must permanently disconnect JB. This will disable the original sound pot. All sound volume adjustments will then be made directly on the amp board.
See a before and after below...
I tried this on three different audio amps (two rebuilt and one original) and it solved the hum in all three cases.
-Sean
I believe I narrowed down what causes the "Nintendo hum" and how to fix it.
I recently picked up a Donkey Kong and a Punch-out. The hum produced by DK was annoying and the PO hum was obnoxious.
After reading though dozens of Nintendo hum related threads I found lots of possible solutions mostly relating to rebuilding the 20ez audio amp or recapping the game's power supply. Most people reported these solutions did not work for them. Others reported using a separate 12v sound amp and some said they designed their own amps for Nintendo games. While others simply stated "that's what Nintendo game do".
I tried the following ...
* Recapped the power supply (didn't help)
* Rebuilt the 20ez audio amp (didn't help)
* Rebuilt the 20ez rectifier circuit (didn't help)
* Put a 430uf cap across the speaker output (this filtered out most of the hum but also made the game sound like you were playing it underwater)
Then I found the last post of this thread...
https://forums.arcade-museum.com/showthread.php?p=3014160#post3014160
The post above suggested unplugging connector JB, moving C379 to the "correct" position and installing a 50k pot at VR371. This made sense as the wire going from connector JB to the adjustment pot board utilized the only shielded cable in the entire cabinet. Eliminating this cable entirely might help. So I ordered a few of these pots http://www.digikey.com/short/3912b7
To be clear, you must permanently disconnect JB. This will disable the original sound pot. All sound volume adjustments will then be made directly on the amp board.
See a before and after below...
I tried this on three different audio amps (two rebuilt and one original) and it solved the hum in all three cases.
-Sean
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