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Several issues with Korg M1
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wolflikeme



Joined: 12 Mar 2013
Posts: 8
Location: Leeds, UK

PostPosted: Sun Aug 28, 2016 5:45 pm    Post subject: Several issues with Korg M1 Reply with quote

Hi.

I'm currently in the process of trying to revive a second hand Korg M1 and have several issues with it.

Firstly, it had clearly been in storage for a few years and was in a messy state. I have give it a good external clean, replaced the battery and made an effort to remove dust, cobwebs etc internally.

I bought a cheap midi interface and all the indication lights are present when transferring the sysex files via sysex librarian on Mac. However, in the program section there are no apparent sound banks. I am met with "Init Program" only. In edit program all the original sound bank titles are present from 1-99, but when pressing any key I'm met with nothing but white noise via headphones (on the headphone socket). In fact, I'm yet to hear any kind of tangible sound. The cheap interface works in the sense that it will allow the M1 to work as a midi controller and play soft synths without obvious latency.

Perhaps I'm doing something wrong? I have followed instructions in terms of altering the global settings on the M1 to allow the sysex transfer but there are no instructions with regards to using sysex librarian with the M1 on Mac. I am given the option to transfer the files to either port 1 or port 2 and have seemingly failed on both counts.

I'm hoping that the white noise issue is down to the cheap midi interface and the failure of transferring the files. I am now awaiting the delivery of a m-audio midi sport 1x1. Hopefully this will correct the problem? I probably should add that I purchased a new kettle lead too. I haven't checked the voltage. Potentially another cause?

My biggest worry is that when pressing the keys g# and a# I get nothing. On all 5 octaves these 2 notes are dead. No white noise when monitoring on headphones and zero response when using as a midi controller. What is the likely issue here? Do I need to clean the key contacts or check all connections internally. Perhaps I need to replace something?

I should add that I'm no electrician and this is actually my first ever hardware synth. Any advice is much appreciated. Cheers.
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voip
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Joined: 27 Nov 2014
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PostPosted: Sun Aug 28, 2016 7:44 pm    Post subject: Reply with quote

I tried to do sysex transfers to an M1 using a cheap MIDI interface and it didn't work. Best success came from using a Kontrol49 as a MIDI interface, and connecting its MIDI out to the M1's MIDI in. This was using Midi-Ox. The settings have already been posted on a previous post but given here again:

Low Level Input Buffers: Size 512 Bytes, Num = 32.
Low Level Output Buffers: Size 65535 Bytes, Num = 512.
Delay Between Buffers 100ms.
Delay After F7 box is checked, and delay set to 500ms.

What is the state of the PCBs inside the M1? Is there much mildew or other damp-related damage? The M1's key contacts are generally very reliable, provided there is no contamination by dust or dead bugs.

The fact that the same keys seem non functional in every octave points to an issue with a keyboard strobe line.

.
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wolflikeme



Joined: 12 Mar 2013
Posts: 8
Location: Leeds, UK

PostPosted: Sun Aug 28, 2016 8:39 pm    Post subject: Reply with quote

voip wrote:
I tried to do sysex transfers to an M1 using a cheap MIDI interface and it didn't work. Best success came from using a Kontrol49 as a MIDI interface, and connecting its MIDI out to the M1's MIDI in. This was using Midi-Ox. The settings have already been posted on a previous post but given here again:

Low Level Input Buffers: Size 512 Bytes, Num = 32.
Low Level Output Buffers: Size 65535 Bytes, Num = 512.
Delay Between Buffers 100ms.
Delay After F7 box is checked, and delay set to 500ms.

What is the state of the PCBs inside the M1? Is there much mildew or other damp-related damage? The M1's key contacts are generally very reliable, provided there is no contamination by dust or dead bugs.

The fact that the same keys seem non functional in every octave points to an issue with a keyboard strobe line.

.


Thanks for your response. Will await the delivery of the Midisport and try the transfer again. Don't think Midi-Ox is available for Mac though, so Sysex Librarian it is. I don't believe that the settings are adjustable, so in that respect, I guess that I'm ok.

The PCB boards looked to be in generally good condition, but I could do with really taking a closer look and probably dismantling it altogether.

When you say keyboard strobe line what do you mean? What would I need to do in order to rectify/identify a problem here?

Cheers.
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voip
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Joined: 27 Nov 2014
Posts: 3758

PostPosted: Sun Aug 28, 2016 10:12 pm    Post subject: Reply with quote

So, for the strobe line(s) -

Each key has a flat strip "common" electrode that can make connection with two contacts, one normally closed (nc), and one normally open (no). The time interval between the "nc" contact opening when the key is pressed and the "no" contact closing is used to calculate the key velocity. This gives a total of 183 connections that need to be made for the 61 key board.

In common with a lot of other devices that need to read inputs from, or produce outputs to a large number of individual elements, e.g. the pixels on a computer LCD screen, or the keys on a keyboard, the M1 keybed uses a multiplexing technique whereby all 5 of the "C" key switch "common" lines i.e. C2, C3, C4, C5 and C6 (for the 61 key board) are connected together, all the "C#" lines are connected together, and so on for the whole keyboard, whilst the key contact pairs "nc" and "no" are connected together in whole octaves, effectively arranging the circuit electronically as a 12 x 10 array for the 61-key board. 12 since there are 12 keys in an octave, and 10 because all of the "nc" contacts in each octave are connected together, and all of the "no" contacts in each octave are connected together, giving 10 bundles of connections. This multiplexing arrangement allows the keybed connection to the rest of the electronics to be made using only 22 wires (well actually 23, because of the extra key C7 at the end), rather than 123, or even 183 wires, giving substantial cost savings.

One set of wires is pulsed, or strobed, sequentially by a driver circuit whilst the other set is read during each pulse, again in a strobe-like manner, allowing the controller to work out which keys have been pressed and their velocity.

So, after maybe a too long explanation, it logically follows that the lines linked to all the G# keys and A# keys may have a bad connection. It could be that two of the contacts in connector C11A have gone open circuit. Removing and reseating the connector may be sufficient to fix this. However, it could also be that the common PCB tracks corresponding to the G# and A# keys have gone open circuit, for some reason e.g. dry solder joint, physical damage, or corrosion, typically.

.
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Escapegoat



Joined: 07 Jun 2016
Posts: 23
Location: Cambridge, UK

PostPosted: Mon Aug 29, 2016 10:40 am    Post subject: Reply with quote

I've also got a slightly poorly M1 (sticky keys and dead buttons in my case, so I can't help on your keyboard problem).

But I did successfully renew the Progs/Combis/etc with the software written by one of our own forumites, see here http://www.korgforums.com/forum/phpBB2/viewtopic.php?t=105746 I think I remember that after the update, I needed to select a new patch for the display to catch up.

Also, to do this I was using a low-cost MIDI interface: https://www.andertons.co.uk/p/UNO/usb-interfaces/midisport-uno-1x1-usb-midi-interface (I have a far better one, but that's not in the same location) It works with the editor/librarian software perfectly in both send and receive modes.

Hope you are sorted soon
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wolflikeme



Joined: 12 Mar 2013
Posts: 8
Location: Leeds, UK

PostPosted: Mon Aug 29, 2016 6:38 pm    Post subject: Reply with quote

voip wrote:
So, for the strobe line(s) -

Each key has a flat strip "common" electrode that can make connection with two contacts, one normally closed (nc), and one normally open (no). The time interval between the "nc" contact opening when the key is pressed and the "no" contact closing is used to calculate the key velocity. This gives a total of 183 connections that need to be made for the 61 key board.

In common with a lot of other devices that need to read inputs from, or produce outputs to a large number of individual elements, e.g. the pixels on a computer LCD screen, or the keys on a keyboard, the M1 keybed uses a multiplexing technique whereby all 5 of the "C" key switch "common" lines i.e. C2, C3, C4, C5 and C6 (for the 61 key board) are connected together, all the "C#" lines are connected together, and so on for the whole keyboard, whilst the key contact pairs "nc" and "no" are connected together in whole octaves, effectively arranging the circuit electronically as a 12 x 10 array for the 61-key board. 12 since there are 12 keys in an octave, and 10 because all of the "nc" contacts in each octave are connected together, and all of the "no" contacts in each octave are connected together, giving 10 bundles of connections. This multiplexing arrangement allows the keybed connection to the rest of the electronics to be made using only 22 wires (well actually 23, because of the extra key C7 at the end), rather than 123, or even 183 wires, giving substantial cost savings.

One set of wires is pulsed, or strobed, sequentially by a driver circuit whilst the other set is read during each pulse, again in a strobe-like manner, allowing the controller to work out which keys have been pressed and their velocity.

So, after maybe a too long explanation, it logically follows that the lines linked to all the G# keys and A# keys may have a bad connection. It could be that two of the contacts in connector C11A have gone open circuit. Removing and reseating the connector may be sufficient to fix this. However, it could also be that the common PCB tracks corresponding to the G# and A# keys have gone open circuit, for some reason e.g. dry solder joint, physical damage, or corrosion, typically.

.


Thanks for taking the time to offer a detailed explanation.

I took apart the M1 today and managed to give the Keybed a good clean. There was lots of dust and even a few dead spiders Smile

I can't find any issue with the PCB boards/connections etc. I did find a hole without a screw on the plastic frame that attaches the key contacts/switches to the keyboard though. I put the screws back in, leaving the screwless hole in a different area. When fixing the key contacts/switches back in place, I managed to accidentally bend a couple of the switches back, but I'm confident that I have put them back to how they were initially.

After fixing everything back together, I'm disappointed to say that the dead g# + a# keys are still out of commission. And on top of that, the first key (c) and the c# sharp on the lowest octave have now stopped working. I can get some joy with the c# when applying hard pressure. Not sure if this is good news or not? Will return to it again in the next day or two. I didn't try to reconnect the C11A connector. Is this one of two connections that sit side by side on the keyboard circuit board?
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wolflikeme



Joined: 12 Mar 2013
Posts: 8
Location: Leeds, UK

PostPosted: Mon Aug 29, 2016 6:42 pm    Post subject: Reply with quote

Escapegoat wrote:
I've also got a slightly poorly M1 (sticky keys and dead buttons in my case, so I can't help on your keyboard problem).

But I did successfully renew the Progs/Combis/etc with the software written by one of our own forumites, see here http://www.korgforums.com/forum/phpBB2/viewtopic.php?t=105746 I think I remember that after the update, I needed to select a new patch for the display to catch up.

Also, to do this I was using a low-cost MIDI interface: https://www.andertons.co.uk/p/UNO/usb-interfaces/midisport-uno-1x1-usb-midi-interface (I have a far better one, but that's not in the same location) It works with the editor/librarian software perfectly in both send and receive modes.

Hope you are sorted soon


Thank you. Hope you get sorted too. Unfortunately, I'd be unable to use the software as I'm on Mac OSX.
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voip
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Joined: 27 Nov 2014
Posts: 3758

PostPosted: Tue Aug 30, 2016 8:24 pm    Post subject: Reply with quote

The C11A connector is one of two connections that sit side by side on the keyboard circuit board KLM-1266. I cannot remember if both ends of the cable assembly are mateable connectors or just on one end. Just remove the connector(s) and re-seat them, preferably with a bit of switch cleaner lubricant like Servisol Super 10, or the Deoxit product. It might be the contact to contact surfaces that might need cleaning, or the crimp between each connector terminal and its wire. The wires can also be individually gently tugged, which may restore a crimped bad connection. If the connector removal and reseating and the wire tugging doesn't work, check the continuity between each soldered connector pin on one board with the corresponding pin on the other, using a multimeter on the low ohms (usually 200 ohms) resistance range, or use the beep continuity test function. The fact that other keys are now not working after opening up the M1 suggests that opening the case produced sufficient disturbance to break the continuity somewhere. The soldering of the relvant pins on IC2 could also be checked. This is a 100 pin QFP (qual flat package) device, and good magnification, ideally a binocular microscope, will be required. Don't forget to take anti-static protection measures when doing any of this.

There is, of course, always a chance the problem could be elsewhere, but this, at least, is a relatively easy thing to do.

.
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wolflikeme



Joined: 12 Mar 2013
Posts: 8
Location: Leeds, UK

PostPosted: Mon Sep 05, 2016 7:26 pm    Post subject: Reply with quote

voip wrote:
The C11A connector is one of two connections that sit side by side on the keyboard circuit board KLM-1266. I cannot remember if both ends of the cable assembly are mateable connectors or just on one end. Just remove the connector(s) and re-seat them, preferably with a bit of switch cleaner lubricant like Servisol Super 10, or the Deoxit product. It might be the contact to contact surfaces that might need cleaning, or the crimp between each connector terminal and its wire. The wires can also be individually gently tugged, which may restore a crimped bad connection. If the connector removal and reseating and the wire tugging doesn't work, check the continuity between each soldered connector pin on one board with the corresponding pin on the other, using a multimeter on the low ohms (usually 200 ohms) resistance range, or use the beep continuity test function. The fact that other keys are now not working after opening up the M1 suggests that opening the case produced sufficient disturbance to break the continuity somewhere. The soldering of the relvant pins on IC2 could also be checked. This is a 100 pin QFP (qual flat package) device, and good magnification, ideally a binocular microscope, will be required. Don't forget to take anti-static protection measures when doing any of this.

There is, of course, always a chance the problem could be elsewhere, but this, at least, is a relatively easy thing to do.

.


Sorry about the late response. I've been waiting on another midi cable in order to restore the sounds. With regards to the connectors on the main board, i managed (with some difficulty) to remove and re-seat. I was surprised to find several microscopic live bugs living in between the connectors! Unfortunately the removal of the live bugs and reseating of connectors has done nothing with regards to usage of g# and a# keys. They're still dead. I tried to remove the connectors that link the main circuit board to the key contact board but they just will not budge? Are the connectors at the end of the key contact circuit board actually removable?

Furthermore, after finally getting the 2nd midi cable that i required, i switched on the M1 today to be met with 'low internal battery'. Just days after a new battery change! Back to square one.

And finally, i succesfully transferred the original sysex files over and they sound like s**t. Mostly white noise and whirring noises, most not even triggered with a key press. This could be down to the sysex librarian settings, but i can't find any guidelines with regards to transferring the files with sysex librarian/mac. The very few things i have read, just state that it worked.

Time to sell as spares/repairs? Not sure that i want to waste any more money now.

Thanks again for your help.
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EdK
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Joined: 23 Aug 2005
Posts: 111

PostPosted: Sun Sep 25, 2016 11:24 am    Post subject: Reply with quote

Hello wolflikeme,

Been reading this thread with great interest. I also have an M1 and thankfully it still works and I use it on a regular basis.

Sorry you're having difficulty restoring yours. You've dived much deeper than I could ever think of doing in fixing it. The most I've ever done to mine is re-solding the output and damper jacks as they get a lot of use as well as a good internal cleaning from time to time.

The only problem I'm having with mine now are the selection buttons (number pad, etc) and their associated tactile switches. Because the tactile switches get harder and harder to activate, I find myself pressing harder on the buttons which tend to break because the plastic has become brittle with age.

I purchased a new set of tactile switches but I'm unable to find the buttons (button groups as they're called). I purchased and replaced most of them quite a few years ago from "parts is parts" but they've been out of stock from quite some time now. Occasionally I might find them on ebay but even then but by the time I notice them, they've been sold.

If you decide to canabilize your M1 for parts, I would be most interested in the buttons from yours.

Thanks...Ed
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wolflikeme



Joined: 12 Mar 2013
Posts: 8
Location: Leeds, UK

PostPosted: Sun Sep 25, 2016 11:55 am    Post subject: Reply with quote

The solution to my issues was to sell the M1 to someone with more capable hands. Thanks for the help though.
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wolflikeme



Joined: 12 Mar 2013
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Location: Leeds, UK

PostPosted: Sun Sep 25, 2016 11:58 am    Post subject: Reply with quote

EdK wrote:
Hello wolflikeme,

Been reading this thread with great interest. I also have an M1 and thankfully it still works and I use it on a regular basis.

Sorry you're having difficulty restoring yours. You've dived much deeper than I could ever think of doing in fixing it. The most I've ever done to mine is re-solding the output and damper jacks as they get a lot of use as well as a good internal cleaning from time to time.

The only problem I'm having with mine now are the selection buttons (number pad, etc) and their associated tactile switches. Because the tactile switches get harder and harder to activate, I find myself pressing harder on the buttons which tend to break because the plastic has become brittle with age.

I purchased a new set of tactile switches but I'm unable to find the buttons (button groups as they're called). I purchased and replaced most of them quite a few years ago from "parts is parts" but they've been out of stock from quite some time now. Occasionally I might find them on ebay but even then but by the time I notice them, they've been sold.

If you decide to canabilize your M1 for parts, I would be most interested in the buttons from yours.

Thanks...Ed


Hope you find the parts you want. Good luck.
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EdK
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Joined: 23 Aug 2005
Posts: 111

PostPosted: Sun Sep 25, 2016 12:37 pm    Post subject: Reply with quote

Thanks. Appreciate the reply.

Someone suggested to me to possibly have new buttons 3D printed.
I looked into that and although 3D printing is reasonably inexpensive, the cost scanning them first is cost prohibitive
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computerchemist1



Joined: 02 Oct 2016
Posts: 6
Location: Warrington, UK

PostPosted: Sun Oct 02, 2016 8:59 am    Post subject: Reply with quote

Hi everyone, I'm not so much hijacking this thread as continuing it from its previous owner - guessing there are that not that many M1s sold in Leeds in the last few weeks with a non working A# and G# and low battery alert!
Some good news - I have cured the low battery alert. Turns out D10 on the main CPU board was shorted in both directions. This meant that there was an excessive current drain back through the 5v positive rail, I measured about 600 ohms which is no wonder the poor battery went flat. Swapped it for a IN4148 and now all is well. I can load the factory defaults and see them on the board.

I haven't looked too closely yet at the A#/G# issue just to say that there IS continuity all the way from the keyboard connector to the pins on IC2.

The noise issue is really doing my head in. It's not the common power supply issues that seem to plague others - I have not only measured perfect levels from the 12-0-12 and 5v rails off the PSU but also the "sub" psu on KLM-1261 which is giving me the 5-0-5V rail too. One question - can someone with a working M1 confirm that the DAC (IC11) has around 9.5v / -9.5v being supplied to it? I desoldered that thinking it was faulty as I can see logic pulses on MOST of the bits going into it - specifically, pins 2-11 on the chip - but no output. Injecting a signal generator into the now unsocketed DAC on pin 25 gives me a signal (although very low) on output. A much louder one the other side of IC13. I tried a replacement DAC with the same result as the previous owner - gated white noise for INIT program and a various cacophony on digital noise for the other factory settings when restored. All connections between CN1B on the DAC board and pins on IC15 on the CPU board look fine. I have also desoldered and tested IC13 (4053) on the DAC board and it passes.
Looking back on this, I can see digital pulses into the DAC but they are obviously bibble, the DAC however does appear to be doing its job, even though I am seeing no pulses on bits 10-16. Can anybody point me in a direction to look at next - do those dynamic RAMs hanging off IC15 just do effects or do you think that 's a good starter?


Dave
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T3owner
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Joined: 17 Jun 2011
Posts: 368
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PostPosted: Mon Oct 03, 2016 3:55 pm    Post subject: Reply with quote

computerchemist1 wrote:
[...]The noise issue is really doing my head in. It's not the common power supply issues that seem to plague others - I have not only measured perfect levels from the 12-0-12 and 5v rails off the PSU but also the "sub" psu on KLM-1261 which is giving me the 5-0-5V rail too. One question - can someone with a working M1 confirm that the DAC (IC11) has around 9.5v / -9.5v being supplied to it?[...]Can anybody point me in a direction to look at next [...]

Many problems with the M1 are related to power supply issues, although they might not be obvious at first. You "measured perfect levels from the 12-0-12 and 5v rails off the PSU" - was that based on voltmeter readings, or did you 'scope them? Bad caps can cause surprisingly high levels of AC at switching frequency to be riding on the DC.

As far as I know, DC to the DAC should be closer to +/- 12v. There shouldn't be significant voltage drops across resistors R80/R79 (10 ohm) or R83/R84 (33 ohm) on the KLM-1261 - if there is, check the values of those resistors, and the related decoupling capacitors (C52/C59, etc.). The resistors can be stressed by leakage in the caps, or even switching "garbage" from the main supply - if C52/C59 are OK, they can cause any garbage to be dropped across R80/R79. That can overheat the resistors and cause their values to rise.
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