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Re: KORG M1 - No sound / Low battery indication. SOLVED!

Posted: Mon Feb 10, 2020 6:32 pm
by Yekuku
Hi, I have the inconvenience of battery low (internal). According to what I read, I initially changed the C23 for a new one, and everything remained the same. Then I changed the rest (c11,19,18,21 ... etc) and it keeps telling me the same error. Any idea what the fault may be? I inherited the keyboard. my father used it to work, and when he died it was me. It was a while without being used and when I turned it on it said that error. I had the programs but did not emit sound. I changed the battery and it was reset and I could not remove that low battery message.
Hi and welcome on the board.
Please confirm that you are getting 12V, -12V and 5V from the power supply.

Re: KORG M1 - No sound / Low battery indication. SOLVED!

Posted: Thu Feb 13, 2020 8:17 pm
by HeMagliano
Yekuku wrote:
Mon Feb 10, 2020 6:32 pm
Hi, I have the inconvenience of battery low (internal). According to what I read, I initially changed the C23 for a new one, and everything remained the same. Then I changed the rest (c11,19,18,21 ... etc) and it keeps telling me the same error. Any idea what the fault may be? I inherited the keyboard. my father used it to work, and when he died it was me. It was a while without being used and when I turned it on it said that error. I had the programs but did not emit sound. I changed the battery and it was reset and I could not remove that low battery message.
Hi and welcome on the board.
Please confirm that you are getting 12V, -12V and 5V from the power supply.
I'm not getting the right voltages. Instead of -12 have 22 And instead of 5 I get 10. The keybord is getting check by a service now But i think i can give him an idea with your help. Thanks!

Re: KORG M1 - No sound / Low battery indication. SOLVED!

Posted: Fri Feb 14, 2020 9:31 am
by Yekuku
Obviously the problem is located in the power supply.
The fact that you are getting 10Volts instead of 5V is bad news, digital components dont like overvoltage.
Good luck, let us know how it goes.

Re: KORG M1 - No sound / Low battery indication. SOLVED!

Posted: Fri Feb 14, 2020 11:09 pm
by HeMagliano
Yekuku wrote:
Fri Feb 14, 2020 9:31 am
Obviously the problem is located in the power supply.
The fact that you are getting 10Volts instead of 5V is bad news, digital components dont like overvoltage.
Good luck, let us know how it goes.
The first was an oxidized welding of a coil (the green things in the power supply). and also an R80 resistor in the DAC. When it is resolved I tell you.

Re: KORG M1 - No sound / Low battery indication. SOLVED!

Posted: Mon Aug 24, 2020 9:06 am
by Leeroy001
Hello, First time poster here. Hello all :)

I have a beat up old Korg M1R which I have been working on, trying to bring back to life. Ive got it to the point where it mostly works. After replacing the battery, loading the default patches I noticed intermittent sound cutting in and out, no pattern to it, all audio, via outputs or headphones, on the demo songs etc. On the weekend I replaced a few of the tactile switches, and noticed the sound drop out slowly getting worse on powerup, ending up after maybe 10 mins having virtually no sound. This afternoon I checked the power supply, have good 5V, -12v, had +12v, then it went away, came back, then went altogether. At this point I have close enough to 0V where should be +12, but have good -12v and good +5V. Capacitors have passed the visual test( no swelling or leakage that I can see). Just wondering if anyone had any advice or tips on measurement points for the loss of the +12v source? I live in a remote location in Australia so components are not just off the shelf for me. I can however order components through a local battery shop. Thanks in advance, this post has some great info so hopefully it gets seen (Oh BTW the board I have is the KLM 1269) thanks again

Re: KORG M1 - No sound / Low battery indication. SOLVED!

Posted: Mon Aug 24, 2020 7:03 pm
by Yekuku
Hi ,
The problem could be the psu but there is a chance that a component on the mainboard is failing short dragging the positive analog power line down.
My bet is that the filtering cap at the end of the psu 12v line needs replacing.
Sorry i am on vacation and i dont have access to schematics

Re: KORG M1 - No sound / Low battery indication. SOLVED!

Posted: Tue Aug 25, 2020 6:55 am
by Leeroy001
Yekuku wrote:
Mon Aug 24, 2020 7:03 pm
Hi ,
The problem could be the psu but there is a chance that a component on the mainboard is failing short dragging the positive analog power line down.
My bet is that the filtering cap at the end of the psu 12v line needs replacing.
Sorry i am on vacation and i dont have access to schematics
Thank you Yekuku for the quick reply. I am measuring voltages at the -12V Gnd Gnd +12v connector on the PSU with the cable disconnected. Interestingly I left if for a few hours, measured again and got 9v at the 12v pin, slowly dropping. Will certainly start with the 2 capacitors, C18 and C19 according to Circuit diagram They look fine but you never know internally. I will take them out and order a couple of replacements. cheers