Roland Juno-D synthesizer gets stuck at startup.

Thread Starter

Yami

Joined Jan 18, 2016
290
Hi guys, I've got a roland Juno-D keyboard in for repair. What had happen was the owner went to turn on the keyboard and the front panel flashed on for a moment and the unit turned off with a burn smell.
Someone before me had a look at it and gave up. I have found the burned component which was the IR led (LED44) which is used for the D-beam. I checked all the components in its path and everything was okay. The tech who checked before me had removed IC8 which is an opamp. So I have replaced it with a new one.

What happens now
When the unit is turned on, the LCD lights up with dark block characters. No leds on the front panel lights up and the keyboard just gets stuck at startup. Sometimes the leds flickers on for a moment and then turns off.
I have checked all the power rails. The 5V and 3.3V rails are good. However the +9V rail shows 7.7V! and -9V rail shows -8.5V (which is in the limit stated on the inverter datasheet). There is no change with the 7.7V even when I disconnected all the other boards which needs the +9V.
I checked the crystals outputs and it shows clean sine waves. The things I check all seems to be ok, and I cant figure out what it could be. I thought that the microprocessors were not resetting on start up so I tried manually resetting it. No difference everything initializes and then gets stuck.

Potential breakthrough
I tired chasing the problem of the leds not coming on - I scoped IC6 which is a D-flip flop, the clock signal was there and all the inputs had square waves, but there were no outputs. A square wave does appear the moment the led flickers.
This is a problem right? But I still cant think why this could be a problem to cause the whole unit to freeze up.
I want to figure out what else could be causing this problem before ordering the flip flop.
Your help is greatly appreciated.
I have included the pdf of the service manual. The circuit diagrams starts from page 31.
 

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Mgaudiousa

Joined Apr 10, 2020
3
Hi guys, I've got a roland Juno-D keyboard in for repair. What had happen was the owner went to turn on the keyboard and the front panel flashed on for a moment and the unit turned off with a burn smell.
Someone before me had a look at it and gave up. I have found the burned component which was the IR led (LED44) which is used for the D-beam. I checked all the components in its path and everything was okay. The tech who checked before me had removed IC8 which is an opamp. So I have replaced it with a new one.

What happens now
When the unit is turned on, the LCD lights up with dark block characters. No leds on the front panel lights up and the keyboard just gets stuck at startup. Sometimes the leds flickers on for a moment and then turns off.
I have checked all the power rails. The 5V and 3.3V rails are good. However the +9V rail shows 7.7V! and -9V rail shows -8.5V (which is in the limit stated on the inverter datasheet). There is no change with the 7.7V even when I disconnected all the other boards which needs the +9V.
I checked the crystals outputs and it shows clean sine waves. The things I check all seems to be ok, and I cant figure out what it could be. I thought that the microprocessors were not resetting on start up so I tried manually resetting it. No difference everything initializes and then gets stuck.

Potential breakthrough
I tired chasing the problem of the leds not coming on - I scoped IC6 which is a D-flip flop, the clock signal was there and all the inputs had square waves, but there were no outputs. A square wave does appear the moment the led flickers.
This is a problem right? But I still cant think why this could be a problem to cause the whole unit to freeze up.
I want to figure out what else could be causing this problem before ordering the flip flop.
Your help is greatly appreciated.
I have included the pdf of the service manual. The circuit diagrams starts from page 31.
hello Yami

did you ever manage to fix this issue, I have exactly the sam issue but the led above the piano button flashes but the unit dosent initialize

many thanks

@Yami
 

Thread Starter

Yami

Joined Jan 18, 2016
290
hello Yami

did you ever manage to fix this issue, I have exactly the sam issue but the led above the piano button flashes but the unit dosent initialize

many thanks

@Yami
Hey @Mgaudiousa - nope no luck yet. I kept the project for now. My suspicion is that the controller is faulty. Do let me know if you find a fix.
Stay safe.
 

Mgaudiousa

Joined Apr 10, 2020
3
Hey @Mgaudiousa - nope no luck yet. I kept the project for now. My suspicion is that the controller is faulty. Do let me know if you find a fix.
Stay safe.
Hello Yumi
thank you for the reply, I’m coming to the same conclusion because all the rails are measuring correctly but it won’t initialize so I will keep you informed if I get a breakthrough but I fear it’s new motherboard time if I can find one cheap enough, don’t want to spend a fortune on it but I would like to have it working again of course. Many thanks Yumi, I’ll let you know.

BR
Mark
 

JoeJester

Joined Apr 26, 2005
4,259
I have a few questions ....

1. Have you performed all the tasks under no audio output listed in the Owners Manual?

2. Have you done a factory reset?

3. Have you tested all the outputs, L/R and Headphone?

4. Do you have an oscilloscope, a DMM, and an audio generator for signal injection?

If you need an Owner's manual, you can either get one online or I can upload one.
 

JoeJester

Joined Apr 26, 2005
4,259
@Yami

I'd like you to recheck the voltages as shown on these two pictures. From that we can start troubleshooting, if you wish to proceed.


on edit ... added two voltages to the main board

PS VOLTAGES.jpgMAIN-BOARD VOLTAGES.jpg
 
Last edited:

Mgaudiousa

Joined Apr 10, 2020
3
@Yami

I'd like you to recheck the voltages as shown on these two pictures. From that we can start troubleshooting, if you wish to proceed.

View attachment 204591View attachment 204592
Thank you Yami

good idea, no problem
Let me recheck these and log my findings. I’ll start with the PSU board again first just in case, makes sense.

as soon as I’ve finished today’s workload I’ll start on it this evening and let you know what I find. I have it opened up on the bench still so shouldn’t take too long. My better test equipment and scope are trapped in my office at the moment but should have good enough equipment to measure the basics at home for now.

thanks Mark
 

Thread Starter

Yami

Joined Jan 18, 2016
290
I have a few questions ....

1. Have you performed all the tasks under no audio output listed in the Owners Manual?

2. Have you done a factory reset?

3. Have you tested all the outputs, L/R and Headphone?

4. Do you have an oscilloscope, a DMM, and an audio generator for signal injection?

If you need an Owner's manual, you can either get one online or I can upload one.
Hey Joe, Thanks for the response:
The Keyboard does not start up at all, nothing on the LCD no Leds turns on as well as no audio (headphone output or L/R). To do any test routine mentioned on the manual LCD needs to be working.
I will also re-check the voltages you mentioned. I would have to dig up the unit though.
I hope we get a response from @Mgaudiousa Mark as well. Seems to me that we are having the same problem.

Thanks and stay safe
 

JoeJester

Joined Apr 26, 2005
4,259
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