Korg Forums

Hello,
After many years I decided to take out of storage my music materials to start back to make some music. After powering up my Korg M1 it told me to replace the internal battery. After replacing the battery and restore the factory presets with Midi-Ox all the factory presets where there. Only problem is every time I start playing a note it comes with heavy hissing sound. all sounds have this. I discovered after playing around with the M1 that the hissing noise stops when I deactivate the effects on the sounds. Mainly reverb and delays, don't seem to be there with chorus effect. Any ideas what could cause this problem?
Thanks

Hi!
It seems you have the same problem as here.

M1 some years not used, battery gone. replaced, restore factory resets and there is the digital distortion on every sound.

I figured out the following:
Routing a sound to output 3/4 has clean sounds. (without effect).

changing the internal wiring to output 3/4 with 1/2 going 3/4 through the headphone amp: distortion with effect on 3/4 and clean output on 1/2 (without the effects).

Checking the manual and wiring diagram leads to the following:

The Digital-Analog-Converter has a multiplexed one-channel output.
So there is only ONE digial-analog converter for all 4 outputs and the output is multiplexed to the outputs 1 to 4.
As channel 3/4 is without any distortion, I guess the effect processing section is affected.

Lowering or switching the effects of by the settings, the distortion gets less. But still there.

The effect section has old DRAM (dynanic ram modules) attached to the effect processor.
My opinion is a defect on one or more RAM-Modules or by the timing or maybe the voltage.

I would like to get my M1 run again.

Hi ,
Thank you for your reply.
Based on my experience and yours it looks indeed as something is up with the effect section. As you I would like my M1 to work again. Do you know if that particular section can be replaced?
Thank you

I'd be checking to see if you have any bulging capacitors or any signs of electrolytics leaking from your caps. A visual inspection is often enough and the repair process of replacing caps is pretty in-expensive and straight-forward if you are capable of soldering. For a tech it would be a walk in the park.

If you check out this link for the 01W, the author also makes a comment about the M1 suffering the same issues.

https://hajo.kessener.net/electronics/k ... nd-repair/

Thank you for your reply and link.
I will look into the leakage of electrolytic. i'm not really a tech but I know someone who could help me with that.
Thank again