Korg Forums Forum Index Korg Forums
A forum for Korg product users and musicians around the world.
Moderated Independently.
Owned by Irish Acts Recording Studio & hosted by KORG USA
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

faulty motherboard.

 
Post new topic   Reply to topic    Korg Forums Forum Index -> Korg Synths (General)
View previous topic :: View next topic  
Author Message
shirreff
Full Member


Joined: 05 Sep 2009
Posts: 149
Location: Northumberland UK

PostPosted: Sat Apr 07, 2012 9:19 pm    Post subject: faulty motherboard. Reply with quote

I have a problem with the motherboard on my korg M1. It just has a loud hissing sound with the real sounds just barely noticeable in the background.
Any Ideas?
_________________
Korg I3, Korg M1, Korg Tr Rack. Korg x3, Cakewalk Sonar.
Back to top
View user's profile Send private message AIM Address
synthjoe
Platinum Member


Joined: 21 Apr 2010
Posts: 1011

PostPosted: Sun Apr 08, 2012 6:31 pm    Post subject: Reply with quote

Does it hiss only when notes are played, or even after power up, without playing anything? What happens if you route sounds to outputs C+D? Do those have the hissing, too? Is this the same on the headphone out?
Back to top
View user's profile Send private message
shirreff
Full Member


Joined: 05 Sep 2009
Posts: 149
Location: Northumberland UK

PostPosted: Sun Apr 08, 2012 6:57 pm    Post subject: Reply with quote

same whatever route, headphones too. Crying or Very sad
_________________
Korg I3, Korg M1, Korg Tr Rack. Korg x3, Cakewalk Sonar.
Back to top
View user's profile Send private message AIM Address
synthjoe
Platinum Member


Joined: 21 Apr 2010
Posts: 1011

PostPosted: Tue Apr 10, 2012 10:44 pm    Post subject: Reply with quote

Only when playing, or even when idle?
Back to top
View user's profile Send private message
shirreff
Full Member


Joined: 05 Sep 2009
Posts: 149
Location: Northumberland UK

PostPosted: Tue Apr 10, 2012 11:09 pm    Post subject: Reply with quote

Only when playing, Confused
_________________
Korg I3, Korg M1, Korg Tr Rack. Korg x3, Cakewalk Sonar.
Back to top
View user's profile Send private message AIM Address
synthjoe
Platinum Member


Joined: 21 Apr 2010
Posts: 1011

PostPosted: Tue Apr 10, 2012 11:50 pm    Post subject: Reply with quote

If you are experienced in electronics, you could program a single monoaural signal (e.g. sine panned to the center, no effects) on the synth and test pin 1 of IC 12 on the KLM-1261 board to see what signal comes out there (e.g. via a small headphone amp, or line input to an amp). Should the signal be clean at that point, then you have some trouble in the analogue demultiplexing circuitry.

Should the signal be corrupted on pin 1, then you could have a fault in the digital part (unlikely) , the D/A converter chip, or the opamp you're taking the signal from (pin 2 of the same IC 12 is directly wired to the D/A, but a current output - you can test that carefully, if you know how to do it). Make sure you check voltages as well - the problem you describe migh also be due to a missing power supply rail voltage.

Maybe a short recording of the noise would be more revealing than a description - but the method above is still valid for checking, regardless. Just in case you want to avoid opening the synth at this stage.
Back to top
View user's profile Send private message
probani



Joined: 24 Apr 2012
Posts: 1
Location: Patzcuaro, Mich., México

PostPosted: Tue Apr 24, 2012 6:52 am    Post subject: Reply with quote

I test the PIN 1 of IC12 on the KLM-1261 board and the wav form is square, this is correct?
with a sound Init
Back to top
View user's profile Send private message Yahoo Messenger MSN Messenger
synthjoe
Platinum Member


Joined: 21 Apr 2010
Posts: 1011

PostPosted: Wed Apr 25, 2012 10:09 pm    Post subject: Reply with quote

No, I'm afraid it is not. It should be similar to the waveform expected on the line output of the synth - which in case of a freshly initialised program should be something pianolike. However, looking at it on an oscilloscope might be deceiving as all four output channels (L+R+3+4) are present in multiplexed form at this point and switching between the channels might look like square wave. Therefore it is better to listen than to look on an oscilloscope. If it is indeed a square signal, it should result in a quite distorted sound - is that what you're experiencing?

You can check the signal on pin2 of the same IC, if the signal is OK (i.e. different from pin1) then you'll have to check R85 (between pins 1 and 2 of IC12) or maybe replace IC12.

Otherwise the problem is likely in the digital part of the synth, or the D/A converter has to be checked.
Back to top
View user's profile Send private message
woodynat2000



Joined: 11 Oct 2017
Posts: 2

PostPosted: Wed Oct 11, 2017 4:03 pm    Post subject: Faulty Korg Reply with quote

This post is old however I have the same issue and just wondered if you ever found a fix? Cheers, Nathan
Back to top
View user's profile Send private message
shirreff
Full Member


Joined: 05 Sep 2009
Posts: 149
Location: Northumberland UK

PostPosted: Wed Oct 11, 2017 4:08 pm    Post subject: Reply with quote

No, sorry. I still have the faulty board
_________________
Korg I3, Korg M1, Korg Tr Rack. Korg x3, Cakewalk Sonar.
Back to top
View user's profile Send private message AIM Address
Display posts from previous:   
Post new topic   Reply to topic    Korg Forums Forum Index -> Korg Synths (General) All times are GMT
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group