So has anyone solved the "Nintendo hum" yet?

MaximRecoil

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So has anyone solved the "Nintendo hum" yet?

I know for a fact that the problem is caused by the amplifier on the Sanyo monitor because I've fed the audio from my Super Punch-Out board directly into powered PC speakers, and it was perfectly clean; zero hum; but I don't know if it is an amplifier design problem or an interference problem resulting from the amplifier being mounted so close to the monitor and/or getting power from the monitor.

Replacing the capacitors and transistors on the Sanyo audio amplifier doesn't solve the problem ... ever.

Someone mentioned a couple of years ago that Mark Spaeth was looking into this. Did anything ever come of that?

It seems to me that a suitably clever person (not me) could design an audio amp that doesn't hum, and have it have the same dimensions/holes/connectors as the Sanyo amp so it would be a drop-in replacement. They could probably sell one (or two) to most people that own a Nintendo cabinet. People who I'd bet have the knowledge and means to do this include Clay Cowgill, Mark Spaeth, Jrok, and probably others.
 
I've always thought that it was the power from the monitor to the audio amp. It's not really regulated and IIRC is basically tapped right after the filter cap. I've never tested that theory, but I believe that was what Mark's solution was.
 
I've always thought that it was the power from the monitor to the audio amp. It's not really regulated and IIRC is basically tapped right after the filter cap. I've never tested that theory, but I believe that was what Mark's solution was.

They make little solid state 3-legged regulator chips that you can attach a heat sink to and could put inline between the power source and the amplifier. I used a 5V version recently to replace a mechanical regulator for the gauges in an old car. I assume the Sanyo amplifiers run off ~12 volts?

I would imagine that your theory could be tested by disconnecting whichever plug powers the Sanyo amplifier and powering it off a separate 12V power suppy (assuming 12V is what it needs). Do you know which plug provides power? There are 3 of them (not counting the audio signal input plug), two 3-prong plugs labeled "JB" and "JC", and one 2-prong plug labeled "JD". I assume it is not the 2-prong "JD" plug because that connects to a separate device (which looks like a small transformer) which then goes to the speaker, which indicates it is the amplified output circuit.
 
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It's the JC connector and it isn't ~12Volts. It's much more then that. Regulated may of been the wrong word, as it isn't really regulated. Filtering would be a better word as the supply is almost right out off the wall and the "hum" everyone hears is the AC ripple.

That's my theory.
 
I'm showing -135.2 VDC on the JC plug. Does that sound right? That seems like a really weird voltage, especially being negative voltage. For test points I used the prong's solder joints on the back of the amplifier PCB, and I put the multimeter's red positive lead on prong #3 (see image below), and the black negative lead on prong #1, and I also tried it with the black negative lead on prong #2 (because both 1 and 2 appear to be ground), with the same results in both cases.

sanyoamp.png


So if I did that right; i.e., if the amplifier really does need -135 VDC, then I guess testing it with a separate power supply is out of the question, right?

By the way, I can see what the JB plug is for now that I've looked at it; it is for the volume pot on the control board (which I'm sure you already know).
 
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No reading whatsoever using ACV, not even a flicker of a reading; it stays rock steady at zero (I tried it on both the 200 and 750 range settings using the same test points that I mentioned above). I also rechecked the DCV while I was at it, and it is still steady at -135.2 VDC.
 
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It seems to me that a suitably clever person (not me) could design an audio amp that doesn't hum, and have it have the same dimensions/holes/connectors as the Sanyo amp so it would be a drop-in replacement. They could probably sell one (or two) to most people that own a Nintendo cabinet. People who I'd bet have the knowledge and means to do this include Clay Cowgill, Mark Spaeth, Jrok, and probably others.
I could easily do that... Do you believe there is a big market for these replacement amps?
 
I could easily do that... Do you believe there is a big market for these replacement amps?

If you can get it made for $30 or less, then yes for me.

Or, to keep things lighter, could you design it as a PCB swap for the DIY crowd? We could transplant the common components to your board, already populated with the 'new' stuff.
 
I could easily do that... Do you believe there is a big market for these replacement amps?

I think there would be, as long as the new amplifier could directly replace the old one without modifying anything in one's cabinet. "Nintendo hum" has been asked about on the internet for many years, and so far I haven't seen a solution beyond the suggestion to replace the capacitors and such on the amplifier, which doesn't work, because the hum is a design flaw. For example, here is an RGVAC post from a dozen years ago:

Sunshine (Elio)
Jan 23 2000, 3:00 am
Subject: Nintendo Donkey Kong Jr Hum sound (need schematics)

Hi.

As you know, most of these Nintendo arcade games seem to have 'speaker hum',
usually low pitched. Even by recapping the little sound amplifier board on
the Nintendo monitor, I still get the hum coming from my machine.

I think that this may be due to the PCB itself (and I have tried different
PCB which do indeed have different bad hum sounds, hence the PCB!!).

It may be the CAPs (electrolitic) on the PCB and I want to try if this is
indeed the problem.

I need the Schematics to the Donkey Kong Junior CPU PCB? Could anybody help
by provide a scan of the area before the Amp out (bottom right corner of
schematic)? The pages of my copy stuck together and the ink is faded now.

This might put an end to these Nintendo Hum problems that everybody has had
and still has....

Thanks.

Link

He was on the wrong track thinking that the problem was with his DK Jr. CPU board however.

By the way, what do you believe is causing the hum in the current Sanyo amplifier design/setup?

If you can get it made for $30 or less, then yes for me.

Or, to keep things lighter, could you design it as a PCB swap for the DIY crowd? We could transplant the common components to your board, already populated with the 'new' stuff.

I agree with all of this.
 
FWIW, my Mario is using a Mike's inverter/sound board and it still hums just as loud as my DK using a capped with new transistor Sanyo audio board.

It might be the game boards and not the amplifier.
 
Heh... I have 9 amplified channels of Nintendo "hum" goodness and we honestly don't notice the hum. I guess if you only have a Nintendo game on and it's pretty quiet you'd notice... but in an arcade full of games the ambient noise definitely drowns it out.

BUT, if there was a simple(and cheap) thing to add to either the power line or audio line to take care of the hum... I'd probably do it. $270 just won't make it happen though. :)
 
FWIW, my Mario is using a Mike's inverter/sound board and it still hums just as loud as my DK using a capped with new transistor Sanyo audio board.

It might be the game boards and not the amplifier.

Like I said, I've fed the audio from my Super Punch-Out board directly into powered PC speakers, and it was perfectly clean; zero hum. I made an adaptor so that I could run RCA cables directly off the audio pins of the SPO board's card edge, and then I ran the cables into my PC's sound card input, which then went to the PC speaker's amplifier and out to the speakers. The audio was perfect. I did it so that I could cleanly record some audio because I had some missing/corrupted sound effects in the game at the time (turned out to be a bad TTL logic chip), and I wanted the recording so that the Nintendo engineer that helped me fix the problem could hear the missing/corrupted sounds himself.

In any event, here is the recording from my SPO arcade machine, and you can hear that there is no hum whatsoever (it is every bit as clean as the comparison recording that I made from MAME at the time to illustrate what the correct sound effects should be):



Maybe Mike's amplifier doesn't address whatever design problem it is that causes the hum. Where do you have it mounted? Have you tried it at various distances from the monitor?
 
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I agree, its still there when using mikes nintendo jamma adapter.

It sounds like it has a design and/or placement problem as well, because I know for a fact that you can get clean hum-free audio from the gameboard when using a different amplifier; at least you can from a PO or SPO board (see above).
 
Has anyone tried a 1:1 audio transformer to see if it's a ground loop issue?

That would be cake to add into the audio circuit between the board and the amp to isolate them.
 
Has anyone tried a 1:1 audio transformer to see if it's a ground loop issue?

That would be cake to add into the audio circuit between the board and the amp to isolate them.

What type of transformer is it that is already there, between the output of the amplifier and the speakers; the one that looks like a small isolation transformer?

sanyoaudiotransformer.jpg
 
No, silly.

Between the board and the amp...

You need a 1:1 audio isolation transformer.
 
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