Korg M1 crashing / defective contact?

faul · Post by **faul** » Wed Mar 18, 2015 2:24 pm

Hello,

i just bought a used Korg M1 Workstation and i noticed that the Korg is kind of "crashing" whilst using it. By crashing i mean that the Display shows the same message as when you start up the Synth ("Korg Music Workstation M1") and after the message disappeared the Korg switches back to programm I00 "Universe". Also, the display is flickering.
I think it might be a defective contact somewhere in the Korg but as i am not really into repairing electronics i thought i better ask if any Korg M1 User had the same problem and can help me to find a solution.

Thanks in advance and sorry for my bad english!
Elias

McHale · Post by **McHale** » Wed Mar 18, 2015 4:29 pm

Don't have an M1 but the first thing I would do is to open it up and unplug and re-plug everything. It sounds like a short someplace which is likely a loose cable or connector.

And your English is fantastic. No need to apologize!

-Mc

the_crimson_thunder · Post by **the_crimson_thunder** » Wed Mar 18, 2015 8:13 pm

Looks as if the M1 loses somewhat contact (power?) and is starting new - that's why the "Korg Music Workstation M1" message appears...
But first I would check the output voltages coming from the power supply - there has to be +12V, -12V and +5V. But be careful: there is main power on the psu when operating - if unsure how to proceed get help from a tech-savvy person!

On my M1 I've replaced all seven electrolytic capacitors - just to make sure they won't fail in the near future - they tend to dry out or leak due to the age of the synth.
And you should immediately check the four electrolytic caps on the mainboard - just some days ago I've had to repair my M1REX - two of that capacitors had leaked onto the mainboard - was no fun to clean the board from the residue - and a trace had been destroyed ("eaten up") by the way. Desoldered the four caps, cleaned the board, put in new caps, repaired the damaged trace and put in a fresh battery - now he's back to life, acting 'as new'

faul · Post by **faul** » Wed Mar 18, 2015 11:13 pm

Thank you both for your fast replies, really appreciating it!
I'm gonna open it up tomorrow and check the cables and voltages. I'll report back then

faul · Post by **faul** » Thu Mar 19, 2015 2:01 pm

Hey guys, i just opened up the Korg and noticed this on the power supply unit. Did the capacitors leak here aswell or could this be glue?
Thanks again!

[/img]

T3owner · Post by **T3owner** » Thu Mar 19, 2015 2:51 pm

faul wrote:Hey guys, i just opened up the Korg and noticed this on the power supply unit. Did the capacitors leak here aswell or could this be glue?

It's glue, and can be troublesome. It may or may not be related to what you're experiencing.

See:
http://www.electronicspoint.com/threads ... rds.61364/

Google "yellow glue becomes conductive hygroscopic" (without the quotation marks) for more.

McHale · Post by **McHale** » Thu Mar 19, 2015 3:19 pm

I've had similar issues with keyboards (one being my Korg Triton) and the issue was caused by bad power coming out of the wall. I started gigging with a UPS which did power conditioning and my problem went away. I also had the same issue with a Roland D-20 and after several hundred dollars in the shop and multiple visits, they determined nothing was wrong with it. Problem again was bad power from the wall.

-Mc

faul · Post by **faul** » Thu Mar 19, 2015 4:35 pm

T3owner wrote:It's glue, and can be troublesome. It may or may not be related to what you're experiencing.

Thanks for the hint, i will try to remove it carefully from the circuit board and see what happens.

McHale wrote:I've had similar issues with keyboards (one being my Korg Triton) and the issue was caused by bad power coming out of the wall. I started gigging with a UPS which did power conditioning and my problem went away.

Thank you, but what exactly do you mean by "bad power"?

I just measured the output of the PSU and it is a bit more than it should be.
I am getting 7,13v on the 5v output and 16,18v on the 12v output. Could that be a problem? And if so, where do i have to search for the cause?

T3owner · Post by **T3owner** » Thu Mar 19, 2015 7:58 pm

faul wrote:[...]I just measured the output of the PSU and it is a bit more than it should be.
I am getting 7,13v on the 5v output and 16,18v on the 12v output. Could that be a problem? And if so, where do i have to search for the cause?

The voltages you measured aren't just "a bit more" than they should be, they are way too high. The M1 power supply is a "switching" or "switch-mode" type. When working correctly and under proper load, the voltages (+5, +12, and -12) should be within about 0.2 (0,2) volts for the +5 and perhaps slightly more for the +/-12.

By all means, remove any of that glue and recheck the voltages.

Is the meter you used known to be accurate? Was the supply output connected when you made the measurements? If not, remeasure.

I just had another thought. You said you just got the M1. What is the line (mains) voltage where you are? What is the proper line voltage indicated on the M1 itself? The power supply will be labled either KLM-1267, KLM-1268, or KLM-1269 - which is in yours?

the_crimson_thunder · Thu Mar 19, 2015 11:41 pm

You should only measure with the psu output connected to the main board (a load) - otherwise the readings will show 'wrong' values due to the psu being a 'switching mode' unit which needs a certain 'load' to operate correct. Good advice so far from T3owner.
'Bad power' means an unstable voltage coming from the wall outlet. If its level fluctuates too much some gear will be caused to 'reset' or act as if you switch OFF the power and immideately ON again.

By turning VR1 you may slightly adjust the voltages to an appropriate level - but adjust in very small amounts while watching the voltages - there's only ONE pot (VR1) that adjusts ALL the output voltages at once. I would set the 5V as close as possible. Mostly the others tend to be 'round 11.8V which is good enough.

faul · Post by **faul** » Thu Mar 19, 2015 11:48 pm

I measured without the Synth connected to the PSU. Just followed your hint and remeasured with the Korg connected, et voilà: +4,7v, +11,2v & -11,2v.
I'm from Germany, we have a line voltage of about 220v. The PSU is labeled as KLM-1269 (220/240).

the_crimson_thunder · Thu Mar 19, 2015 11:53 pm

Möönsch, sach' doch watt...

P.S. wir sollten mal PM'men.. jetzt geht's allerdings in's Bett. Ich schaue morgen hier wieder rein...

T3owner · Post by **T3owner** » Fri Mar 20, 2015 1:48 am

faul wrote:I measured without the Synth connected to the PSU. Just followed your hint and remeasured with the Korg connected, et voilà: +4,7v, +11,2v & -11,2v.

If you haven't already done so, I'd remove the yellow glue - even if it's not sufficiently conductive to cause problems, it can corrode component leads. As the_crimson_thunder mentioned, VR1 will adjust all the voltages (due to coupling via PC1), but setting the +5 correctly will likely bring the +12 and -12 within spec.

faul wrote:I'm from Germany, we have a line voltage of about 220v. The PSU is labeled as KLM-1269 (220/240).

Good, apparently you have the correct supply.

Bis Morgen. (I'm not from, nor in, Germany.)

theskindiver · Post by **theskindiver** » Thu Aug 06, 2015 11:10 pm

I'm now having this same issue, random rebooting whether it's idle or being played, it just reboots and presents the Universe patch... Did you ever figure it out?

synthjoe · Post by **synthjoe** » Sat Mar 26, 2016 8:48 am

Replacing 30 years or electrolytic capacitors is never a bad idea...