Korg M1: No sound on left output but headphones work fine

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brucewillis
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Korg M1: No sound on left output but headphones work fine

Post by brucewillis » Tue May 18, 2021 9:17 am

Hello Community,

I'm new here, as I proudly bought a Korg M1 synthesizer last week. Now I have the following problem for which I might get some good advice here:
Although the headphone output works without complaint, the left line-out channel is dead. Obviously it is not due to contact difficulties.
A look at the service manual shows that both the headphone output and the line-out channels 1 and 2 are fed by the same transistors (Q3 and Q4). Now the question arises what the problem could be...?

Are there any settings in the Korg that deactivate the left channel? I already looked in the settings and "Local" is set to "ON". So I am at the end of my ideas here. Does anyone have a clue?

Many thanks in advance.
Bruce
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meatballfulton
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Re: Korg M1: No sound on left output but headphones work fine

Post by meatballfulton » Tue May 18, 2021 1:04 pm

The obvious thing to check first is the wiring to the output jack. It could be the jack has failed (though there's not much to fail in a jack!), a bad solder joint or some other open circuit issue.
I listened to Hatfield and the North at Rainbow. They were very wonderful and they made my heart a prisoner.

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Tekhed66
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Re: Korg M1: No sound on left output but headphones work fine

Post by Tekhed66 » Tue May 18, 2021 3:03 pm

brucewillis wrote:
Tue May 18, 2021 9:17 am
Hello Community,

I'm new here, as I proudly bought a Korg M1 synthesizer last week. Now I have the following problem for which I might get some good advice here:
Although the headphone output works without complaint, the left line-out channel is dead. Obviously it is not due to contact difficulties.
A look at the service manual shows that both the headphone output and the line-out channels 1 and 2 are fed by the same transistors (Q3 and Q4). Now the question arises what the problem could be...?

Are there any settings in the Korg that deactivate the left channel? I already looked in the settings and "Local" is set to "ON". So I am at the end of my ideas here. Does anyone have a clue?

Many thanks in advance.
Bruce
My money is on a dry joint or a bad component such as a dead capacitor or resistor... I had almost the exact same problem with my M1 about 3 months ago with the main audio out (L worked, R didn't) ... If you look through my previous posts, you'll see all of the various bits of help and advice I received (thanks Yekuku!!!) ... in the end, it was because of a bad solder join on one of the capacitors that I had replaced on the D/A board.... one quick poke with a hot soldering iron later and it was all fixed .... these old synths are pretty tough and some repair jobs can turn out to be very simple ... good luck!

brucewillis
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Re: Korg M1: No sound on left output but headphones work fine

Post by brucewillis » Wed May 26, 2021 9:31 am

Hello, I would like to give a short feedback: It was indeed a bad solder joint on the line-out jack. :oops:

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