Question about Donkey Kong with a Sanyo 20Z2Aw in it

ArcRevival

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Question about Donkey Kong with a Sanyo 20Z2Aw in it

I have to say that Nintendo monitors are still a little foreign to me so maybe someone can figure this one out.

Picked up a DK where someone started to put a 20Z2AW from a Punchout in it but did not quite finish it. The plug for sound was plugged into the inverter board and the plug from the chassis that is supposed to go there was just left hanging. The video cable was going to the inverter board but since the audio was plugged into to it instead of the power from the chassis it had no picture. I put the video cable from the board straight to the chassis.

The game had no picture or sound but the monitor was coming on with high voltage. Figured out where the sound plug was supposed to go on the audio board and moved it over. Bypassed the inverter board as it's not needed for DK. Now I have a picture and it looks great but volume is very low, can barely hear it and I mean barely. Volume pot didn't really make a change other than to bring it up to where I can just hear it.

I installed new caps on the audio board and here is where the big question comes in. There is a place for the cap at c378 but it was not populated like it is on a 20ez. Do I need to install that cap ? Does this monitor have the wrong audio board ? I don't see that cap in the 20z2aw schematic. I ohmed out the speaker, it checks good. I tried a second boardset, same volume level. I still need to verify the pot is good but am still wondering about that cap at C378.
 
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The good news is that it isn't causing your audio problem. It's a cap for the power section.

C378 is kind of an odd ball that some have them and some don't. You may have just solved the riddle. Everyone refers to all the Sanyo Monitors as 20EZ when there are actually different models. That and they call them Nintendo monitors even though they were made by Sanyo and other game manufacturers used them.

Sanyo must of decided not to populate that cap for some reason.
 
Ok. I just didn't want to spend a lot of time troubleshooting if I had the wrong audio board or something. I will see what else I can figure out.

Thanks.
 
i have always added that cap and had no problems doing so.

did the two transistors on the audio amp test good?

Peace
Buffett
 
The volume pot meters out ok and has continuity to the audio board. Am I correct to think that the issue almost has to be on the audio board ? The speaker ohms out and there is continuity to the little transformer from the speaker.
 
check the big fusible resister on the edge of the audio amp board.

that can cause audio distortion/loss of audio as well.

sorry i cant remember the location and i am not at home to check.

and have you installed the missing cap??

Peace
Buffett
 
check the big fusible resister on the edge of the audio amp board.

that can cause audio distortion/loss of audio as well.

sorry i cant remember the location and i am not at home to check.

and have you installed the missing cap??

Peace
Buffett

That fusible resistor is at R383, it is 39 ohms. This is the only one that seems to fit the bill that I could find on Mouser.

Hewitson said:
Maybe the lack of that cap is what causes some of these amps to buzz?

If you're referring to "Nintendo hum" then no, it makes no difference at all. I have several examples of both versions of the Sanyo amp here; i.e. the ones from Z2AWs have no C378 cap while the amps from 20-EZVs do have that cap. They both hum in their stock form, and a Z2AW amp still hums after adding the C378 cap.
 
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I metered every resistor including that one and they all check out ok. Also failed to mention that I have all the correct voltages at the motherboard. I did not put in that cap but it doesn't sound like I need it ?
 
I did not put in that cap but it doesn't sound like I need it ?

No you don't need it. It doesn't hurt anything to add one, but adding one doesn't noticeably affect anything at all in my experience.

You don't have another know-to-be-working-properly Sanyo audio amp you could try in it? That would tell you for sure whether the amp is the problem or not.

And what is the ohms reading on the speaker's voice coil?
 
That fusible resistor is at R383, it is 39 ohms. This is the only one that seems to fit the bill that I could find on Mouser.

that's the one i was thinking of.

i had one that tested good but was bad i replaced it and had full volume.

cant hurt to sub it out and see.

Peace
Buffett
 
I replaced TR373 and TR374 and volume is unchanged. I unplugged the speaker and metered it at the plug going to the speaker and got 4.3 ohms.
 
It's definitely the monitor. I found my other 20ez in the garage that I had picked up from an Operator. It was untested but I sat it behind the game and plugged it all in and have normal volume.

My next question, can I just put that audio board in the other monitor. It does have the cap at C378 . Looks like they are the same otherwise ?
 
I populated the cap and swapped audio boards and still low volume but the original audio board works in the other monitor. Getting warmer lol.
 
Finally got this one. It was actually the volume pot after all. I had metered it but what I could not see was a crack on the other leg . Doh !

At least it's working now and I learned more about the audio section of a DK than I ever cared to know lol.
 
Good catch. I was just out in the garage looking at one of my sanyos, and I was going to post that it has to be either the pot or the small transformer on the chassis. Glad it was an easy fix, even if it took a while to find it.
 
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