Still acting weird? Ground problems!Just when I thought I had fixed all the problems with the Juno-60, I noticed it started jumping into manual mode and acting weird again when I was mocing the sliders.
DCBI put the Juno-60 on the workbench and tested it for a while.
As I expected the sliders to be causing the problem I kept wiggling them, pushing the front panel to check if there were any faulty connections somewhere causing this.
I put the Juno-60 back in the rack and tested it. Seemed to work fine. Odd...
Then a couple of days later when I tried it again, the same problem appeared! Argh!!!
Luckily, I found some information in the Juno 60 service notes, p 19.
"Because of the AC ground, a "ground loop" may be created when the DCB cable is connected between the Juno-60 and its party (equipment). As a result, a certain-level digital noise may occur. In the later Juno-60 the noise is considerably reduced by rearrangement of ground paths together with installation of Panel Board B improved version, 052H411C (pattern relayout).
The modification is conducted at the factory on the units with serial numbers 253800 and subsequent.
For the units prior to SN253800, alternative modification can be made for the purpose of noise reduction."
Well well! Guess if my Juno has an older Panel Board B and lower SN than 253800.
Also, since I don't connect anything to the DCB jack when the Juno was on the workbench I never saw the problem there. Annoying!
There's a picture in the service manual describing the modification.
I didn't really analyze it that much but I guess it separates the ground into two areas on the panel board instead of letting everything share the same ground.
This is done by cutting a trace and soldering a wire at the cut, while the other end of the wire should be soldered to ground on the PSU board.
Here's what it looks like in my Juno-60 after I did it.
|Black ground wire ends marked with dashed yellow circles.|
Here are close-ups of the two wire ends.
|Anode of D2 on PSU board.|
|Trace cut and wire soldered to pin marked 81 on Panel Board B.|
I haven't had any problems with it since then!
Also, I replaced the two broken 3-way switches for the arpeggio mode and range selectors.
So finally, I can play with the arpeggiator :D