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View topic - Game Gear 2 asics: mono sound from the speaker doesn't work

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  • Joined: 29 Mar 2013
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  • Location: Italy
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Game Gear 2 asics: mono sound from the speaker doesn't work
Post Posted: Thu Feb 23, 2017 8:48 pm
Hi guys

I've got a 2 asics chip Game Gear in which the "mono" sound doesn't work.
I mean that for game musics/sounds composed of 2 different channels, from the speaker you can here only one channel (I don't understand if the right or the left one). While from the hearphone jack you have both!
You could say it's the sound card but it's not! Because I changed it with the one of another game gear I've got and it does the same (and the one of the Game Gear with the problem works well on the other GG).

What have I to check? There is continuity on the 5 wires cable from the GG to the soundboard...it's not the problem.

I don't know how the "mixture" of left and right channels works and so I don't know what I've to check to solve the problem...

Obviously we are talking of fully recapped GG and soundboards...


To explain better the problem:
mono music: all right
stereo music (whit different tones from the left channel and the right one), eg. "splash wave" of Out Run game (in which the problem is very evident) you can hear only a part of the sound, while you can hear all of it using hearphones (different tones from left to right)
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  • Joined: 31 Oct 2007
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  • Location: Estonia, Rapla city
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Post Posted: Thu Feb 23, 2017 9:51 pm
There's a switch in the headphone connector that controls if output is stereo or mono, if that switch fails in some way you will get the effect you describe.
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  • Joined: 29 Mar 2013
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Post Posted: Thu Feb 23, 2017 10:24 pm
TmEE wrote
There's a switch in the headphone connector that controls if output is stereo or mono, if that switch fails in some way you will get the effect you describe.


Thank you but I said that the soundboard is good. I tried it on another GG and on it works fine!
So I tested another (perfectly working on the other GG) soundboard on the GG with the defect and it has the same problem.
It seems the problem is on the GG motherboard...but...how?!

I really don't understand...
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  • Joined: 04 Dec 2016
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  • Location: Guarulhos - SP - Brasil
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Post Posted: Fri Feb 24, 2017 3:46 am
game gearer wrote
TmEE wrote
There's a switch in the headphone connector that controls if output is stereo or mono, if that switch fails in some way you will get the effect you describe.


Thank you but I said that the soundboard is good. I tried it on another GG and on it works fine!
So I tested another (perfectly working on the other GG) soundboard on the GG with the defect and it has the same problem.
It seems the problem is on the GG motherboard...but...how?!

I really don't understand...


Check IC6 on Main board, Pin 3 and 5 is audio in from ASIC and Pin 1 and 7 are audio out.

Pin 5 is Left Audio In and pin 7 is Left Audio Out.
Pin 3 Is Right Audio In and pin 1 is Right Audio Out.

If you want I have a schematic of main board in high definition on my Website
http://neto-games.com.br/esquemas/esquema_gg_2_asic_placa_principal.png
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Post Posted: Fri Feb 24, 2017 7:17 pm
Neto wrote
game gearer wrote
TmEE wrote
There's a switch in the headphone connector that controls if output is stereo or mono, if that switch fails in some way you will get the effect you describe.


Thank you but I said that the soundboard is good. I tried it on another GG and on it works fine!
So I tested another (perfectly working on the other GG) soundboard on the GG with the defect and it has the same problem.
It seems the problem is on the GG motherboard...but...how?!

I really don't understand...


Check IC6 on Main board, Pin 3 and 5 is audio in from ASIC and Pin 1 and 7 are audio out.

Pin 5 is Left Audio In and pin 7 is Left Audio Out.
Pin 3 Is Right Audio In and pin 1 is Right Audio Out.

If you want I have a schematic of main board in high definition on my Website
http://neto-games.com.br/esquemas/esquema_gg_2_asic_placa_principal.png



Thankyou....thanks to your schematics I checked all and I found that the problem is the "SPON" or "SPKON" signal from pin 25 of IC-3 to the soundboard (so to the CN3 connector)

On the GG with working stereo/mono sound this signal is positive....while on the not working one it's negative!!!! Exactly the opposite! 4,48 V vs - 4,53 V!!!
This starting from the chip...

The rest is ok and the same.
L and R signals are ok.
Infact, as I said, with headphones you can hear stereo sound.
It's the speaker that doesn't have the two channels mixed in a mono sound!

What is it? Is there a way to solve?
I immagine that SPON or SPKON is for SPEAKER ON
But I really don't know how it works...and what it does....
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  • Joined: 04 Dec 2016
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Post Posted: Sat Feb 25, 2017 12:32 am
game gearer wrote
.....

Thankyou....thanks to your schematics I checked all and I found that the problem is the "SPON" or "SPKON" signal from pin 25 of IC-3 to the soundboard (so to the CN3 connector)

On the GG with working stereo/mono sound this signal is positive....while on the not working one it's negative!!!! Exactly the opposite! 4,48 V vs - 4,53 V!!!
This starting from the chip...

The rest is ok and the same.
L and R signals are ok.
Infact, as I said, with headphones you can hear stereo sound.
It's the speaker that doesn't have the two channels mixed in a mono sound!

What is it? Is there a way to solve?
I immagine that SPON or SPKON is for SPEAKER ON
But I really don't know how it works...and what it does....


Looking into schematic you will see a transistor marked as Q1 2SC1623 connected to SPKON Line, check this transistor.
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Post Posted: Sun Feb 26, 2017 6:08 pm
Neto wrote
game gearer wrote
.....

Thankyou....thanks to your schematics I checked all and I found that the problem is the "SPON" or "SPKON" signal from pin 25 of IC-3 to the soundboard (so to the CN3 connector)

On the GG with working stereo/mono sound this signal is positive....while on the not working one it's negative!!!! Exactly the opposite! 4,48 V vs - 4,53 V!!!
This starting from the chip...

The rest is ok and the same.
L and R signals are ok.
Infact, as I said, with headphones you can hear stereo sound.
It's the speaker that doesn't have the two channels mixed in a mono sound!

What is it? Is there a way to solve?
I immagine that SPON or SPKON is for SPEAKER ON
But I really don't know how it works...and what it does....


Looking into schematic you will see a transistor marked as Q1 2SC1623 connected to SPKON Line, check this transistor.


There was a problem with that component...thank you very much!
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