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M1 requires trouble shooting
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yoshi88
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Joined: 27 Apr 2007
Posts: 133

PostPosted: Sat Nov 03, 2018 3:52 am    Post subject: M1 requires trouble shooting Reply with quote

Just got this M1.

Problem:

No screen illumination... that was later solved after seeing the main board did not receive its 5.5V from the 4 pin connector.

Rebooted.... screen now works

All buttons seem to respond. But NO sound on any outputs.

Low battery error message. Powered off, removed battery and tested it V = 0.4V! Then replaced old original 2032 with new 3.3V battery.

Tried factory reset. Low battery message still reads.
Tested the battery on rear of board. V= 3.3V

Still no sound from outputs.

Connected another keyboard Via MIDI.

M1 master and remote keyboard slave:
Midi messages transferred and can hear keyboard note selections on other board.

Other keyboard Master and M1 slave.
No sound coming from M1!!!!

Where to go from here!
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the_crimson_thunder
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Joined: 18 Nov 2014
Posts: 92
Location: Germany

PostPosted: Sat Nov 03, 2018 10:47 am    Post subject: Reply with quote

Go to GLOBAL - Page 5.1 (MIDI Global) and see if eventually 'Local' has been set to 'OFF' - if yes: set to 'ON' and try again... hope it helps Wink

Regards,

Michael (aka the_crimson_thunder)
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yoshi88
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Joined: 27 Apr 2007
Posts: 133

PostPosted: Sun Nov 04, 2018 12:15 am    Post subject: Reply with quote

Korg M1

Cleaned the Cr2032 contacts. inserted battery again = 3.3V
Error Message : Low battery remains.

Factory reset 3 times : Low battery remains
No Sound!

Loaded M1Preload Successfully : Original Factory Data intact onboard M1

NO Sound!

Tested Midi ports:

Connected External keyboard
M1 transmits MIDI data as a midi controller on other device perfectly!


Connected External midi device as controller , M1 as receiver:
Sound Test:
NO sound from Korg M1!

Midi Test:

Selected SEQUENCE on M1 , engaged record + used external keyboard to input notes:
Result was perfect on playback of KORG's MIDI song played on EXT. keyboard.

All KORG Sequenced material was played back on External keyboard successfully.

This old M1 can send and receive MIDI, but it can not play.

Also strange is the joystick does zero out on the axis.

I suspect A/D.

There is stain on the power board beneath inductors and cap.

Your thoughts?
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T3owner
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Joined: 17 Jun 2011
Posts: 368
Location: USA

PostPosted: Sun Nov 04, 2018 1:07 pm    Post subject: Reply with quote

yoshi88 wrote:
[...] There is stain on the power board beneath inductors and cap.

Your thoughts?

Is the "stain" actually yellow/brown glue? If so, that material can deteriorate and absorb moisture from the air, becoming conductive. Depending on what component leads it's touching, it can upset power supply voltages. I suggest that you remove any such glue and make sure that the supply voltages are correct and stable before doing any other work.
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yoshi88
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Posts: 133

PostPosted: Sun Nov 04, 2018 8:37 pm    Post subject: Reply with quote

What are the standard voltages and their locations?
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T3owner
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Joined: 17 Jun 2011
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PostPosted: Sun Nov 04, 2018 10:43 pm    Post subject: Reply with quote

yoshi88 wrote:
What are the standard voltages and their locations?

See https://elektrotanya.com/korg_m1_sm.pdf/download.html
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yoshi88
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Joined: 27 Apr 2007
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PostPosted: Thu Nov 08, 2018 2:14 am    Post subject: Reply with quote

I have made the assumption that the Volume control is functional.

But what if it isn't?

How can I test this?

The Slide VR is located on M1 board 1262.
The part is a 10KBx2 ( RS 30112AC0JA )

Can I safely jumper this from beneath. Would anyone know which pins looking from the underside can be jumped to test the circuit.

These slide pots are still available for ordering.

Your thoughts?
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Last edited by yoshi88 on Thu Nov 08, 2018 2:17 am; edited 1 time in total
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yoshi88
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Joined: 27 Apr 2007
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PostPosted: Thu Nov 08, 2018 2:15 am    Post subject: Reply with quote

I have made the assumption that the Volume control is functional.

But what if it isn't?

How can I test this?

The Slide VR is located on M1 board 1262.
The part is a 10KBx2 ( RS 30112AC0JA )

Can I safely jumper this from beneath. Would anyone know which pins looking from the underside can be jumped to test the circuit.

These slide pots are still available for ordering.

Your thoughts?
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voip
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Joined: 27 Nov 2014
Posts: 3758

PostPosted: Thu Nov 08, 2018 2:42 pm    Post subject: Reply with quote

Is there any audio on outputs 3 and 4?
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yoshi88
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Joined: 27 Apr 2007
Posts: 133

PostPosted: Sun Nov 11, 2018 6:52 pm    Post subject: Reply with quote

[quote="voip"]Is there any audio on outputs 3 and 4?[/quote route signal to

Re routed signal to 3 and 4?

Presently NO headphone jack sound
Presently NO Audio on 1 & 2 ( default settings )
Presently NO audio on 3 or 4 ( default settings )
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yoshi88
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Joined: 27 Apr 2007
Posts: 133

PostPosted: Fri Nov 16, 2018 5:51 am    Post subject: Sound is back on M1 - slight buzz heard Reply with quote

T3owner wrote:
yoshi88 wrote:
[...] There is stain on the power board beneath inductors and cap.

Your thoughts?

Is the "stain" actually yellow/brown glue? If so, that material can deteriorate and absorb moisture from the air, becoming conductive. Depending on what component leads it's touching, it can upset power supply voltages. I suggest that you remove any such glue and make sure that the supply voltages are correct and stable before doing any other work.


fault on the power board found #1269. At Connection # 12, Voltages were not +/- 12V at one connection that eventually led to the jack-board.
Capacitor leaked and since replaced Voltages are stable. Sound on all outputs!!!

Noticeable buzz on sound.

Not sure where to hunt next.

Any thoughts
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M3 61 expanded
Triton Extreme 88 & 61
Triton PRO X 88
Trinity V3 61
O1WFD 61
T3 61
M1 61
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Last edited by yoshi88 on Fri Nov 16, 2018 4:50 pm; edited 6 times in total
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T3owner
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Joined: 17 Jun 2011
Posts: 368
Location: USA

PostPosted: Fri Nov 16, 2018 8:39 am    Post subject: Re: Sound is back on M1 - slight buzz heard Reply with quote

yoshi88 wrote:
fault on the power board found #1261. Voltages were not +/- 12V at one connection that eventually led to the jack-board.
Capacitor leaked and since replaced Voltages are stable. Sound on all outputs!!!

Congratulations.

 
yoshi88 wrote:
Noticeable buzz on sound.

Not sure where to hunt next.

Any thoughts

Disconnect everything but the power cord - no audio or MIDI cables. Plug in headphones. Is the "buzz" heard on the 'phones?
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yoshi88
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PostPosted: Fri Nov 16, 2018 5:20 pm    Post subject: Reply with quote

After connection was fed proper + _ 12v from psu on board 1269... sound was heard. The sound is more distortion and less buzz, heard on all outputs. With headphone jack connected only, still distortion persists.

This M1 has been in storage for over 12 uears in non working condition. The owner had a previous tech say his M1 was dead...gave no more details on why and returned it.. so it remained unused snd i got it.
This M1 is 30 years old.

I dont have a working Esr meter... so a careful check of caps is needed.
The glue on psu corner on board 1269 was cleaned off... one resistor was surrounded by the substance ... most of it removed.

Any thoughts and where to hunt for the source will be greatly appreciated.

Thanks T3!
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T3owner
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Joined: 17 Jun 2011
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Location: USA

PostPosted: Fri Nov 16, 2018 7:00 pm    Post subject: Reply with quote

Many distortion problems are caused in the DAC circuit, which is sensitive to voltage. The KLM-1261 board has a power supply area (at lower left on the schematic) where the +/- 12v from the kLM-1269 is further filtered, and regulated down to +/- 5v. What voltages do you see on all the points labeled "B" through "M" on that part of the schematic? Please give readings to two decimal places.

Also, do you have an oscilloscope?
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yoshi88
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Joined: 27 Apr 2007
Posts: 133

PostPosted: Sat Nov 17, 2018 4:00 am    Post subject: Reply with quote

T3owner wrote:
Many distortion problems are caused in the DAC circuit, which is sensitive to voltage. The KLM-1261 board has a power supply area (at lower left on the schematic) where the +/- 12v from the kLM-1269 is further filtered, and regulated down to +/- 5v. What voltages do you see on all the points labeled "B" through "M" on that part of the schematic? Please give readings to two decimal places.

Also, do you have an oscilloscope?


My power supply board is KLM 1268 117CN
Cap #18 was shot and replaced.
Excess glue removed from this region. There is plenty of old glue still around caps by CN#9 of 1268.

I will find a good ground and test ( 1261 ) in regions B , C , L and M Correct?
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