Korg ES1 no sound out

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Rvahunter
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Korg ES1 no sound out

Post by Rvahunter » Thu Jan 03, 2019 3:59 am

I picked up a korg es1 electribe used (deadbeat seller so it mine now, no return..long story) and it turns on but I get no sound out. all the manual says is check the normal stuff - make sure your amp works, etc.. the one thing i am not sure how to attack is their last suggestion which is "Has the volume been lowered by a MIDI Master Volume message", what's best way to accomplish that?

alternately has anyone dealt with this issue that can let me know other possibilities to fix it?

Hope it doesn't get down to some board level electronics issue here...

Thanks!

Rasputin
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Re: Korg ES1 no sound out

Post by Rasputin » Thu Jan 03, 2019 3:14 pm

A few things:

viewtopic.php?f=3&t=96712

- You could try using the firmware in that thread to reflash/reset the whole system.

- There is a special 7V rail specifically for the analog portion of the ES-1. The regulator could be bad. If so, you'd have no sound.

- The volume knob could be bad. If so, no sound.

- There's the DAC and also one specific amp (TDA1308, IC9) which could be bad, and that would kill all the sound.

I'm assuming the headphones and the main outs are both dead, yes?

Rvahunter
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Re: Korg ES1 no sound out

Post by Rvahunter » Fri Jan 04, 2019 6:37 am

Yea, no sound from headphones or main audio outs. figure i will take the back off and like around with my multimeter this weekend.

Thanks for the info, sounds like you know your stuff!

Rasputin
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Re: Korg ES1 no sound out

Post by Rasputin » Fri Jan 04, 2019 9:56 am

Rvahunter wrote:Yea, no sound from headphones or main audio outs. figure i will take the back off and like around with my multimeter this weekend.

Thanks for the info, sounds like you know your stuff!
Be careful not to short anything or zap the equipment or yourself!

Assuming the full ES-1 reset doesn't do anything, check the ROHM BA07 7V regulator. Might be easiest to just look at the positive side of C15 to verify the 7V rail is good. No 7V = no sound. Fix regulator and/or supporting circuit.

7V is good? Then check the signal at the volume knob. The volume knob (VR2, Alps RK09K12C) input can be tested at pins 3 and 5, and the outputs at pins 2 and 4.

If there's input but no output then it's very likely just the knob.

If 7V rail was good and you've got output from the volume knob then check Q5, 2SA812-T1B which is the MUTE signal transistor. If that's not working then all the outputs will be disabled.

If there's nothing at the volume knob *input* then you've got more serious problems: :(

Dead IC9 = both channels dead before volume knob

IC9 is getting power but no input signals on pins 2 3, 5, or 6? That's probably starting to get into real trouble like the Asahi Kasei Microdevices AK4522VF DAC or the DSP system. At that point, it might be more prudent to part it out.

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