No sound on NEO-AES

[chaoticjelly]

I bought a Japanese AES to use as my own personal machine, it is one of the original green box rental units. It loads cartridges just fine, with no errors, however there is no sound at all.

This is the original revision of mainboard (NEO-AES).

I have tried the headphone socket with a pair of headphones, but no sound there either. If you turn the volume up very loud, there's just a constant hum, that changes ever so slightly every now and then.

The only other post I can find with a similar issue is this one; and unfortunately, the original poster does not update as to whether the problem was solved or not.

http://www.neo-geo.com/forums/showthread.php?t=107576&highlight=aes+sound

I have checked the mentioned 4.7K pull up resistor at pin 56 of the YM2610 and it is high, so it seems that a dead YM2610 may not be the problem? Is there any other way to test this IC?

I do not think that the problem is the electrolytics around the opamps, since the system is in extremely good shape and seems to have been stored well in its original box, however I have not attempted to test them.

Does anyone have any repair tips please? I was wondering if there is any way I can construct something to connect up, to output sound at certain stages on the mainboard, what would I need to make to do this, and which stages should I check first?

I have not really troubleshooted/repaired an audio problem before, except for bad capacitors on other systems.

 

[channelmaniac]

There's a D/A converter that takes the digital output of the 2610 and converts it to audio. Check the inputs and outputs of that chip with a logic probe. It also uses an op-amp for feedback into that D/A converter.

If you have sound out from there then check each component down the line until you find the problem.

An oscilloscope or a logic probe with beep helps here. You can hear the beeping of the probe in beat with the music. hehehehe. Sounds freaky.

RJ

 

[chaoticjelly]

There's a D/A converter that takes the digital output of the 2610 and converts it to audio. Check the inputs and outputs of that chip with a logic probe. It also uses an op-amp for feedback into that D/A converter.

If you have sound out from there then check each component down the line until you find the problem.

An oscilloscope or a logic probe with beep helps here. You can hear the beeping of the probe in beat with the music. hehehehe. Sounds freaky.

RJ

The D/A converter? That's the YM3016 isn't it?

Hmm I have checked the inputs and outputs with a logic probe and they are all HIGH.

My probe unfortunately does not have a beeper.. I thought it did but no..

I don't have an oscilloscope either..

I also checked the inputs and outputs from the BA10324 that the outputs from the YM3016 go to, and they are HIGH too..

 

[ttooddddyy]

The D/A converter? That's the YM3016 isn't it?

.

Yes it is, if you put your finger on the output pins do you get a hum/buzz from the audio output ?

 

[chaoticjelly]

Yes it is, if you put your finger on the output pins do you get a hum/buzz from the audio output ?

Yeah, when I use my finger there is a low hum, sort of a "wheeeee" noise.

If I touch either of the output pins with the logic probe it makes a "pop".

 

[chaoticjelly]

I think I'm just gonna try and get an oscope.

I presume that I will be able to see the sound waveforms on the oscope CRT when I probe around?

 

[channelmaniac]

Yes.

However, the noise you get when you touch the outputs of the D/A converter and the lack of pulses on the input leads me to believe the 2610 is out.

 

[chaoticjelly]

Hey RJ,

Thanks for that, hmm I guess that would be pretty logical.. is there a pinout for the YM2610 anywhere?

I was hoping it wasn't that chip.. where am I supposed to find another?