Hi i list!
I am troubleshooting an i3 that has a very weak volume output. The volume is weak on the main and headphone outs.
When I pulled it out of storage, the volume was weak. i played the keys heavily, the volume crackled then it played at a normal level.
I tried to play it at a band practice and the volume disappeared.
I opened it up, contact cleaned the sliders, inspected the board, checked the connectors and put it back together. I did not see any cracked solder joints.
The volume is very weak as if there is no power to the audio output circuit. The sliders function perfectly without any crackling.
I suspect the non-polar coupling capacitors are bad, or the harness between the board and the audio outs might be faulty, or the power filter capacitors might have a problem.
Anyone have any experience or advice, please! Thanks for reading!
Sam in NJ
i2 i3 Very Weak Volume Output
Moderators: Sharp, X-Trade, Pepperpotty, karmathanever
-
samriccijr
- Full Member
- Posts: 118
- Joined: Thu Jan 01, 2004 11:13 pm
- Location: usa nj
I have fixed many Korg I3's in my time. I never knew about this forum though, seems like there are many users which have problems with Sound/Display issues.
Here's a link...
http://adriangin.wordpress.com/2013/06/ ... -korg-i3s/
I have found that there are many users online which have this wonderful Korg Arranger. I’ve fixed one which had poor display and no sound output. I’ll list what went wrong.
#1 Fading backlight on LCD Display Screen. Although the display screen works, it can be difficult to see the text without a backlight. Firstly check that the contrast control works. Sometimes the contrast level is turned all the way up/down and you can’t see the text.
If the backlight is broken, you can replace the LCD perhaps an LED type 240×64 LCD display. You can get brandnew LCDs with LED backlights there on Aliexpress.com quite cheaply about $20 USD. You need the T6963 type LCDs. Remember also that the EL backlight on the original LCD needs about 100VAC which the internal inverter takes care of. If you are replacing it with an LED display, please use 5V
.
#1a Unit turns on, LCD goes ‘black’ and no lights or keys / sound comes on. I have found one cause of this to be the powersupply +5V not starting up quick enough. The work around solution is to place a 10uF capacitor from RESET to Ground.
Where is the RESET pin? Fine the big D70433GD Microcontroller located on the Bottom Right of the Main Processor board.
Get the link here: http://pdf1.alldatasheet.com/datasheet- ... 2-5BB.html
Find Pin 8, and follow it around to the Specialised KORG MB622E 15 IC. There is a place where you can easily solder a capacitor between this RESET line and ground.
#2 Bad Capacitors. Does your Korg i3 smell like fish? Because if it does, corrosive electrolyte from the capacitors has leaked allover the board! Terrible! This causes tracks to be damaged and can cause open circutis and short circuits too.
Other than a visual and nasal inspection you can probably find the damaged capacitors.
#3 Still no sound? I’m not sure why but the Headphone / Line output ports of the i3 are controlled with quite a few of these NPN transistors. (Which have a non-conventional SOT23 1-B 2-C 3-E pinout, most SOT23 NPNs have 1-B, 2-E, 3-C.. but anyway) I found that these NPN are connected in common emitter mode (Emitter is tied to ground) the audio signal is passed in the Collector and the base is controlled by this ‘interesting’ circuit.
I didn’t bother finding out what this interesting circuit does, it probably does something, but I’m not sure. I also found that all these NPN bases are all commoned. I found the voltage base control circuit output 1.4V and all the NPNs were fully on. Hence the loss of sound (it got grounded!)
You’ll also see that there is a 1MOhm resistor pulling the base output to the -12V Rail, but it’s too weak to have any effect.
So to get sound, simply HardGround / Shortcircuit the base output to 0V. Yay the NPN’s don’t turn on and we get sound!
#4 I also had an issue with the PCM69 DAC… it didn’t seem to be outputting any sound despite Digital audio data being put in. So I replaced it with a PCM1781. The PCM1781 output also has to go in after the first stage OPAMP otherwise you’ll get really bassy sound. I also noticed that at high volumes there is digital distortion which is not good. Does anyone else get this on their Korg i3 at MAX all volumes? The distortion is not related to headphone clipping as the master volume is an analogue control not a digital control like the rest.
Hopefully that helps you guys get things fixed!
Taking and putting back together a Korg I3 is really a pain as there are a lot of screws needing to be taken out. Especially with the Display you pretty much need to take it all out before being able to have access to the display module LCD.
Here's a link...
http://adriangin.wordpress.com/2013/06/ ... -korg-i3s/
I have found that there are many users online which have this wonderful Korg Arranger. I’ve fixed one which had poor display and no sound output. I’ll list what went wrong.
#1 Fading backlight on LCD Display Screen. Although the display screen works, it can be difficult to see the text without a backlight. Firstly check that the contrast control works. Sometimes the contrast level is turned all the way up/down and you can’t see the text.
If the backlight is broken, you can replace the LCD perhaps an LED type 240×64 LCD display. You can get brandnew LCDs with LED backlights there on Aliexpress.com quite cheaply about $20 USD. You need the T6963 type LCDs. Remember also that the EL backlight on the original LCD needs about 100VAC which the internal inverter takes care of. If you are replacing it with an LED display, please use 5V
.#1a Unit turns on, LCD goes ‘black’ and no lights or keys / sound comes on. I have found one cause of this to be the powersupply +5V not starting up quick enough. The work around solution is to place a 10uF capacitor from RESET to Ground.
Where is the RESET pin? Fine the big D70433GD Microcontroller located on the Bottom Right of the Main Processor board.
Get the link here: http://pdf1.alldatasheet.com/datasheet- ... 2-5BB.html
Find Pin 8, and follow it around to the Specialised KORG MB622E 15 IC. There is a place where you can easily solder a capacitor between this RESET line and ground.
#2 Bad Capacitors. Does your Korg i3 smell like fish? Because if it does, corrosive electrolyte from the capacitors has leaked allover the board! Terrible! This causes tracks to be damaged and can cause open circutis and short circuits too.
Other than a visual and nasal inspection you can probably find the damaged capacitors.
#3 Still no sound? I’m not sure why but the Headphone / Line output ports of the i3 are controlled with quite a few of these NPN transistors. (Which have a non-conventional SOT23 1-B 2-C 3-E pinout, most SOT23 NPNs have 1-B, 2-E, 3-C.. but anyway) I found that these NPN are connected in common emitter mode (Emitter is tied to ground) the audio signal is passed in the Collector and the base is controlled by this ‘interesting’ circuit.
I didn’t bother finding out what this interesting circuit does, it probably does something, but I’m not sure. I also found that all these NPN bases are all commoned. I found the voltage base control circuit output 1.4V and all the NPNs were fully on. Hence the loss of sound (it got grounded!)
You’ll also see that there is a 1MOhm resistor pulling the base output to the -12V Rail, but it’s too weak to have any effect.
So to get sound, simply HardGround / Shortcircuit the base output to 0V. Yay the NPN’s don’t turn on and we get sound!
#4 I also had an issue with the PCM69 DAC… it didn’t seem to be outputting any sound despite Digital audio data being put in. So I replaced it with a PCM1781. The PCM1781 output also has to go in after the first stage OPAMP otherwise you’ll get really bassy sound. I also noticed that at high volumes there is digital distortion which is not good. Does anyone else get this on their Korg i3 at MAX all volumes? The distortion is not related to headphone clipping as the master volume is an analogue control not a digital control like the rest.
Hopefully that helps you guys get things fixed!
Taking and putting back together a Korg I3 is really a pain as there are a lot of screws needing to be taken out. Especially with the Display you pretty much need to take it all out before being able to have access to the display module LCD.
-
samriccijr
- Full Member
- Posts: 118
- Joined: Thu Jan 01, 2004 11:13 pm
- Location: usa nj
Adrian, Thank you so much! I suspected the mute circuit was the culprit. This saves me time removing surface mounted capacitors on the rail...
I will replace the 220 uf capacitor while I am there. I was even considering to update the 100uf and 47ufs on the 5/12V rails.
The schematic of the mute circuit is attached. Please bless if my notes match your description. I will photograph the mod when I get home.
<p><img src="http://home.comcast.net/~samriccijr/i3mutemod.jpg"></p>
The distortion is digital, but sometimes it goes away and the sound clears up. When I re-start, then the output is weak and the distortion comes back. It is not a dirty fader, the volume response behaves like it is muted until the fader is at about 75 percent.
Thank you again,
Sam Ricci, Jr.
Dividing Creek, NJ USA
I will replace the 220 uf capacitor while I am there. I was even considering to update the 100uf and 47ufs on the 5/12V rails.
The schematic of the mute circuit is attached. Please bless if my notes match your description. I will photograph the mod when I get home.
<p><img src="http://home.comcast.net/~samriccijr/i3mutemod.jpg"></p>
The distortion is digital, but sometimes it goes away and the sound clears up. When I re-start, then the output is weak and the distortion comes back. It is not a dirty fader, the volume response behaves like it is muted until the fader is at about 75 percent.
Thank you again,
Sam Ricci, Jr.
Dividing Creek, NJ USA
Hi Sam,
Yes you are correct! Ground that 1MOhm to the screw!
I've uploaded photos...
http://adriangin.wordpress.com/2013/06/ ... -korg-i3s/
Thanks to you I now know of the biblical service manual! Nice find, that would have saved me some time lol!
Let me know how you get on!
Yes you are correct! Ground that 1MOhm to the screw!
I've uploaded photos...
http://adriangin.wordpress.com/2013/06/ ... -korg-i3s/
Thanks to you I now know of the biblical service manual! Nice find, that would have saved me some time lol!
Let me know how you get on!
-
samriccijr
- Full Member
- Posts: 118
- Joined: Thu Jan 01, 2004 11:13 pm
- Location: usa nj
ITS ALIVE!!! Clear loud sound and perfect slider control!
I am good for another month or 12....
Thank you Adrian!
Modders beware: The mute circuit is disabled after this mod.
You will hear pops when you turn the i3 on.
It is good practice to lower the master volume before you turn the unit on.
Here is my mod, sorry for the average solder work:
<p><img src="http://home.comcast.net/~samriccijr/i3mutejumper.JPG" width="800"></img></p>
As Adrian explained, I jumpered the Q7 side of R39 (1Meg) to the ground
plane by the screw. I did not replace the 220uf capacitor - It is not
needed since the 6 other transistors are disabled. Maybe I will replace it
when I fix the backlight, before it leaks onto the motherboard!
Best,
Sam in NJ USA
I am good for another month or 12....
Thank you Adrian!
Modders beware: The mute circuit is disabled after this mod.
You will hear pops when you turn the i3 on.
It is good practice to lower the master volume before you turn the unit on.
Here is my mod, sorry for the average solder work:
<p><img src="http://home.comcast.net/~samriccijr/i3mutejumper.JPG" width="800"></img></p>
As Adrian explained, I jumpered the Q7 side of R39 (1Meg) to the ground
plane by the screw. I did not replace the 220uf capacitor - It is not
needed since the 6 other transistors are disabled. Maybe I will replace it
when I fix the backlight, before it leaks onto the motherboard!
Best,
Sam in NJ USA
Sam,
I have a question.
My Korg i3 seems to have quite a bit of noise, at maximum master volume, when i press the ARR, SONG, PROG, EDIT PROG etc buttons on the left hand side, I hear a high pitched squeal. Similar to that of Laptop headphone outs.
Also when I play a sound loudly and let it die away I hear this strange 'weee-weee-waahh wahh' at the end like digital noise.
Do you get something similar or are your outputs extremely quiet?
Cheers,
Adrian
I have a question.
My Korg i3 seems to have quite a bit of noise, at maximum master volume, when i press the ARR, SONG, PROG, EDIT PROG etc buttons on the left hand side, I hear a high pitched squeal. Similar to that of Laptop headphone outs.
Also when I play a sound loudly and let it die away I hear this strange 'weee-weee-waahh wahh' at the end like digital noise.
Do you get something similar or are your outputs extremely quiet?
Cheers,
Adrian
-
samriccijr
- Full Member
- Posts: 118
- Joined: Thu Jan 01, 2004 11:13 pm
- Location: usa nj
Adrian:
The outputs of my i3 are clean. There is no noise when I press the mode
buttons. There is no crosstalk when a sound decays.
Route the floppy power supply underneath the motherboard, away from
the data cables.
Move the mainboard power harness away from the data or keyboard
harnesses.
Dress the data and audio cables as shown in the service manual. Use the
two black cable ties that are mounted in the case of the i3.
This should reduce any crosstalk you might be hearing.
If lead dress does not work, consider to replace some capacitors.
Refer to the 01/w threads for tips, with the caveat that surface mount
capacitors require a different technique.
Best,
Sam
The outputs of my i3 are clean. There is no noise when I press the mode
buttons. There is no crosstalk when a sound decays.
Route the floppy power supply underneath the motherboard, away from
the data cables.
Move the mainboard power harness away from the data or keyboard
harnesses.
Dress the data and audio cables as shown in the service manual. Use the
two black cable ties that are mounted in the case of the i3.
This should reduce any crosstalk you might be hearing.
If lead dress does not work, consider to replace some capacitors.
Refer to the 01/w threads for tips, with the caveat that surface mount
capacitors require a different technique.
Best,
Sam
Korg i3 problem
Hi to all ...
I have a problem with korg i3.
There is a very weak output/volume on both LR otputs and Headphones, and on max volume like a distorsion.
The sliders are fine, and there is no noise when you slide.
I applied a mod(jump from R39 to ground) but still the volume is weak, and there is a lack of bass when you play.
the capacitors seams in good condition, no leckage.
It's maybe a PCM69 ???
On AdrianGin picture the R39 is removed, i did the mod like SAM suggested.
Tnx
What could be the problem , anyone please help.
I have a problem with korg i3.
There is a very weak output/volume on both LR otputs and Headphones, and on max volume like a distorsion.
The sliders are fine, and there is no noise when you slide.
I applied a mod(jump from R39 to ground) but still the volume is weak, and there is a lack of bass when you play.
the capacitors seams in good condition, no leckage.
It's maybe a PCM69 ???
On AdrianGin picture the R39 is removed, i did the mod like SAM suggested.
Tnx
What could be the problem , anyone please help.