Juno 106 Stereo/Mono Output Problem/Confusion

[JRJR]

Hello!

hope you're all doing well. Just bought a used Juno 106 that has some weird behaviour.

I do get signal on the mono out but not from the stereo out.
Headphone jack is working in stereo.

I opened it up and checked the PCB, re-soldered the jacks, tried to clean them up. Did not work.
When looking at the PCB it seems as if both mono and stereo jacks get fed from the same source (which should not be the case for stereo). And then I do get a signal when the TRS is only halfway inserted.

Could someone explain me what is going on here and how I could get a stereo signal?

Thanks a lot

Cheers
Janik

 

[synthiaks]

How does the schematic look?

 

[synthiaks]

Google helped me quick enough

The flowchart in the Service Manual tell me that the "Stereo" Outputs from the chorus goes to the dual volume potentiometer then to the outputs L/R AND the L/R headphone amps.

If someone has done something else on your PCB then that is not correct

S

 

[aomahana]

Hi,

I have an MKS-50, the rack version of the Juno 106.
The output jacks are not balanced.
Have you tried using TS mono  leads (normal guitar cables), for the outputs?

 

[JRJR]

Yes, I tried unbalanced cables as well. Same thing.
I just measured the jacks and I definitely get current through the cable to the solder joints.
What I don't get:
If you follow the traces on the PCB (picture above) both Jacks have a ground connection and then two pins (hot, cold?).
Pin 1 is connected to Pin 2 on the other jack and vice versa. What is the point here?

I'm confused.

 

[Rob Flinn]

Can I suggest joining this group https://www.facebook.com/groups/vintagesynthrepair/

They will know how to help you !

 

[synthiaks]

Without reading the manual I would say this is a classic Mono/Stereo setup.

Two Mono output Jack's, one labelled Mono if only a plug is inserted there the L/R chorus signal will both be present as a Mono signal. If Both outputs are plugged tha signal split into L and R Jack. This is just as you do with normalled patchbays.

I would be surprised if this wasn't explained in the manual but 80s Roland-Manuals sometimes are "Funky shit"

S

 

[JRJR]

Thanks! Will post there, too.

@Synthiaks: That's what I was thinking as well. It just does not work right now.

 

[synthiaks]

If the Headphones work the output jacks are wonky

The signal to the headphones amps are taped from the same trace as the output Jacks so one (or both) Jacks have some problem.

 

[JRJR]

Thanks guys!

I traced down the signal and it's the jack that breaks the connection.
Still I don't quite understand why L is connected to R and the other way around.

The only explanation I came up with is that if only one is plugged in L&R are summed to mono on the other one and if both are plugged in the connection opened resulting in separate outs for L and R.

 

[radardoug]

Its very straightforward if you study the schematic. When you plug in one jack, it breaks the normalling connection on that jack. But the other normalling connection will mix the two outputs. Works for plugging in either jack. With both plugs in, both normals are broken. So stereo out.

 

[synthiaks]

Thanks guys!

I traced down the signal and it's the jack that breaks the connection.
Still I don't quite understand why L is connected to R and the other way around.

The only explanation I came up with is that if only one is plugged in L&R are summed to mono on the other one and if both are plugged in the connection opened resulting in separate outs for L and R.

Almost ALL vintage "Stereo" Synth outputs do this. Nothing strange at all

.So the problem was that you inserted a TRS cable in the Output not labeled MONO and was expecting a stereo signal, Or was there anything wrong with the Jacks?

 

[JRJR]

I found the issue.

Someone replaced the jacks before but damaged the PCB (probably too much heat) so there was no signal going to the other jack.
I added two wires - here we go. Thanks for all your help!

The pitch bend PCB isn't doing anything as well - let's see what is wrong here and get the beauty back up again.

 

[synthiaks]

I found the issue.

Someone replaced the jacks before but damaged the PCB (probably too much heat) so there was no signal going to the other jack.
I added two wires - here we go. Thanks for all your help!

The pitch bend PCB isn't doing anything as well - let's see what is wrong here and get the beauty back up again.

Well that's nice to hear, Now fix the rest and enjoy!