Crackling Juno output

[flo]

My Juno 106 always had a problem that it started to go 'crackling' after an hour or so. I had a tech replace 2 voice chips but it never went away (...).

Today I wanted to record it but the crackling starts already after a few minutes. It is like a 'static noise' crackling with pops and very small bursts of noise, that goes on for a minute, then shuts up completely for 10 seconds, and then restarts spitting.

I went into test mode etc. I am sure it is NOT a dying chip. The crackling noise is produced without any key hit (and the single voices sound fine). I can also completely silence the VCA level (so that the synth does not make any sound anymore) - still crackling. Also through the headphone out it can be heard.

Only remedy is turning down the volume haha.

Is this the 'amplifier' of the output? Similar problems on other synths? I browsed the net but all juno 106 issues seem to be related to the voice problems.

Thanks for any hint.

..and a nice weekend to all. I dumped the patch into the mks7 and will record that one now

Cheers flo

[Adam Inglis]

A quick look at the schematic suggests the chorus circuit comes after the VCA level control, and then there's a dual op-amp buffer before the signal reaches the headphone amps and the line outs, so the problem could be in either of those two areas.

Does the crackle still occur if you turn off the chorus?

Did the tech tell you he couldn't fix it?

[flo]

Thanks for the detailed answer! The noise occurs with the chorus disengaged, buth it will be 'chorussed' when switched on (maybe that means it is 'produced' before the chorus (?).

The tech was honest then and said that some noise occurs after a few hours of use (of course he also insisted that there actually were two faulty voice chips before adding to the problem). Now it takes the crackling just less longer to start.

[Folderol]

Looking at the schematic, the signal goes sort-of through the chorus section regardless. My first suspects would be C14, C12, C7 (on the jack board). Anther suspect would be C46 which decouples the supply to IC8 & IC9 which are the chorus delay line chips.

[flo]

Would these items be 'regular electronics stuff' that I could replace with 'trial and error' or are they specific things like the voice chips that are quite expensive? In other words, do you think I can try replacing one by another (I can do a bit if soldering although I have not much knowledge of electronics) or is that just going to cost me *another* juno (as the first repair job did...)?
Appreciate your help.

[liquid_808]

I had a similar problem with my Juno, I changed the audio cable connecting the Juno to my mixer, to a thick insulated audio cable, and it fixed it, not sure it will solve your problem, but worth a try.

[Folderol]

It's very difficult to tell from the drawing, but it looks like they are all standard electrolytics, in which case you can replace them with any modern equivalent. Provided you get the polarity, voltaage and value right you certainly won't do it any harm. It's debatable whether it would be worth using modern solid capacitors, but again it would do no harm - just cost a bit more.

[Folderol]

I had a similar problem with my Juno, I changed the audio cable connecting the Juno to my mixer, to a thick insulated audio cable, and it fixed it, not sure it will solve your problem, but worth a try.

If it was a lead problem, turning down the volume wouldn't reduce it.

[Ricoche]

Hi flo,

I am currently experiencing the exact same problem with my Juno 106. I was curious if you ever found the solution to your problem.

Thanks!

Jim

[flo]

Hi Jim

I have not resolved it unfortunately!

Good Luck
flo

[torinkrell]

Sometimes problems are easier than they may initially seem. On my Juno 106 the output volume pot caused crackling.
With the synth off I just "exercised" the volume pot as well as the "LEVEL H M L" switch on the back for a bit and my noise problem was cured.
Even replacing these parts would be rather inexpensive. Best of luck!