R3 suddenly has no Right channel anyone else ?

Rexy · Post by **Rexy** » Tue Feb 16, 2010 3:50 am

My R3 right channel has decided to not make sound anymore today

....coincidently a day earlier the overall stereo level was lower than all my other synths in the recording session, so as a workaround I had to jack up the line gains at the console in order to get a recordable signal from the R3... Has anyone else ever experienced this with their R3 ? The mono/L jack still works. Is there a hard reset or diagnostics routine that a technician would invoke. I already did the factory preload restore that didn't help.
Thanks

axxim · Post by **axxim** » Tue Feb 16, 2010 10:34 am

Hmm, you are the third one reporting this problem with the R3 since about a week

http://www.korgforums.com/forum/phpBB2/ ... 6d9d67af01)

I think it's about time you and your affected mates get together and try to find out any common symptoms/causals (new equipment added, audio/power routing changed/reconnected) and eventually ask Korg's support.

For all of us, I hope this is not an incoming epidemy

Edit: If smomeone is thinking of opening the R3 by himself, please take detailed pictures of the electronic board so we can see what is inside (specially the output section!)

Rexy · Post by **Rexy** » Tue Feb 16, 2010 5:44 pm

I've sent a letter to Korg Technical support and gave them the links to this thread. Thanks for your reply, awaiting Korg's.

rgiskard · Post by **rgiskard** » Wed Feb 17, 2010 5:49 pm

If possible, could you share their answer here?

My R3 left and right channels died this weekend. Decided to check the synth's amp board. Very easy to get to - just remove every screw on the bottom and it comes loose. Taking three more screws off the back and disconnecting some cables I could take the board away from the synth. Found nothing obviously wrong by visual inspection, so I plugged in my oscilloscope, voltimeter and phones to check out if I could find something else... And the problem stopped. Both channels working flawlessly on headphones and individual outputs. Go figure.

rgiskard · Post by **rgiskard** » Wed Feb 17, 2010 5:51 pm

axxim wrote: Edit: If smomeone is thinking of opening the R3 by himself, please take detailed pictures of the electronic board so we can see what is inside (specially the output section!)

Will do if I need to open it again. Is it ok to share those pictures here (i.e. won't Korg object)?

axxim · Post by **axxim** » Wed Feb 17, 2010 10:03 pm

I think not! The photos you take are your copyright and I never heard it is forbidden to post photos of the interior of anything except it has military top secret or whatever else government nature....

So If you say the board functions now. Are the audio outputs and the rest on one board or is there a sepparate audio connectors board? Could you identify the opamps or ICs in charge for the outputs? (thats why I wanted the pictures)

If there is an extra audio board it may have a faulty/dirty/corroed connection. Depending of the PCB material (was it green or either light brown?) it could be a cold soldering or broken cooper trace which is very common for the second type.

rgiskard · Post by **rgiskard** » Thu Feb 18, 2010 12:31 am

The output board has 3 kinds of ICs. There's a BAJ0BC0 voltage regulator and two kinds of amp-ops from JRC: 4580 and 4556AD. The latter seems to be only used for the headphones output. Every other amp-op is a 4580. Board ID seems to be KLM-2731 - I wonder if it would be possible to order one directly from Korg.

Since the problem went away, I didn't bother following the connectors or IC circuits. Also, it would be hard to fix anything. All those surface mount components are a pain to work with. All I did was removing all the connectors and putting them back. That suggests cold solders or bad electrical contact somewhere.

http://www.alldatasheet.com/datasheet-p ... 4580D.html
http://www.alldatasheet.com/datasheet-p ... 556AD.html

Bottom view of the whole R3, output board within blue outline:

By tprado, shot with DSC-W220 at 2010-02-17

Output board with some notes:

By tprado, shot with DSC-W220 at 2010-02-17

axxim · Post by **axxim** » Thu Feb 18, 2010 1:18 am

Nice pictures!

You are right with the OpAmps. Well it is very unusual that they get damaged under normal condition.
The PCB basic material is Fiberglass based FR4 which is standard today so my theory of a cheap board material propense to solder and/or trace faults (like the one for the keyboard itself) is not applicable.

Probably the problem are the connectors going to the audio board.

Thanks for the pics, I had my R3 but was waiting for warranty to expire to open it.... now I sold it. Maybe this will encourage others with the problem to do the same but TAKE ADVICE: To open such a device without knowledge in electronics and its handling may damage it! It also will void the warranty

xmlguy · Post by **xmlguy** » Thu Feb 18, 2010 6:48 am

With most stereo synths, the Left and Right channels have a peculiar property: notice that one output says L/MONO while the other says R. That means that when a jack is plugged only into the left channel plug, then you get a monophonic sum of the L+R channels, but when you plug in a jack to the right plug, then the left channel becomes ONLY the left channel and not the sum. It does this by having a different kind of plug on the Right channel - where the tip is a SWITCH and an output, where the switch is normally closed when no plug is inserted, and opens when you plug the jack in. If there is some problem with this switch, that could cause the L+R outputs to be summed mono and sent only to the left output jack. If the switch is normally open - and stays open, that would explain the problem, or if the switch is normally closed and stays closed, that could also do it. It will act as if you didn't put anything into the jack.

To diagnose this problem, I would build a patch with two distinct tones for the Left and Right Channels, then listen what happens to the L/Mono channel when you plug a jack into the Right output jack. You should start by hearing both tones from the L/MONO output, then only hear one after inserting the plug in the R output. If you still hear both tones - the problem has to be in the switchover from two separate channels to mono-sum. The headphone output should be unaffected either way, since it should be getting audio from the L+R channels separately before the summing stage.

rgiskard · Post by **rgiskard** » Thu Feb 18, 2010 10:44 am

That's a good idea, xmlguy. I'll give it a try. In my R3 case, both the right channel output and the right channel on the phones output got muted. Even so, it's a good test, it might be related.

EDIT:
Headphone output isn't affected when a cord is plugged on the L out. I'll try the test again in case the problem reappers.

oOjTgOo · Post by **oOjTgOo** » Sat Sep 22, 2012 7:00 am

Late to the ball like clockwork.... Lol
I am having an the same/opposite issue. I don't have the left channel. And now that I've just about mastered sampling, I cannot sample the basslines I've been tweaking for several months.
When using the headphone jack the left audio crackles and faintly plays during a peak load. And on mono it's very faint.
Right channel is crystal.
So... I'm not taking it apart. Compressed air? Non-Flamable electric contact cleaner? Or just my local tech?
Thanks in adavance!

kc2ine · Post by **kc2ine** » Sat Sep 22, 2012 4:15 pm

not good, it's look like bad soldering around the outputs

I read somewhere it's common problem for korg R3.
I would take soldering gun and re-solder all places around the outputs,
because something like that can be not even visible.

oOjTgOo · Post by **oOjTgOo** » Sat Sep 22, 2012 7:53 pm

I'll check that out later. I was able to run TS cables from both mono/L and right output into the audiobox and it worked fine. Got some awesome samples until about 6 this morning. Lol.
So it has to be the headphone jack.

sohatyi · Post by **sohatyi** » Sun Sep 23, 2012 10:53 am

The left right crackling on r3s is often due to the ribbon cable that goes from the front to the back of the board being lined up in a certain way. Mine was like that, adjusted the ribbon, problem went. I think it gets interference (doesn't look like a short).

kc2ine · Post by **kc2ine** » Mon Sep 24, 2012 12:12 am

here the another guy having the same problem found the cause and solution:

http://jahgee.xanga.com/724820233/korg- ... put-works/

I opened up the R3, immediately after having problems with the sound yet again. I had incredibly low volume (even with the master volume dial maxed) and fuzziness all around. I poked around very carefully to see what I could touch/move/jostle to change the sound at all. This meant I had the R3 wide open, while plugged in and turned on. I don't recommend doing that with any electronic device any more than you absolutely have to. Anyway, I hit the jackpot. The problem I had was caused by a set of five wires, apparently receiving interference, that simply had to be wiggled a bit, and the problem went away immediately. I couldn't even re-create the problem when I tried to. This, of course, doesn't mean the problem won't come back, but it does mean that I (and hopefully you, the reader) can fix it completely, quickly and efficiently every single time it does.