Roland’s Juno-106 is one of the most popular polysynths ever made. It is simple to use, it sounds warm and lush and along with it’s signature chorused pad sounds it is a versatile bass synth with it’s single oscillator per voice, it’s DCO architecture keeps it in tune and you would have to work really hard to make it sound bad. It’s an instant gratification machine that has been an ever present part of modern electronic music. Many 106’s have now passed their 30th birthday and are still going strong, but what about the future of these instruments? Is it possible to keep them going for another thirty years? Here are some ways to do so, and a timely warning.
First, the easy stuff…
It is good practice to go around all of your gear periodically and exercise every pot, switch, key and control and to insert and remove a jack several times into every socket to prevent build up of tarnish on the contact surfaces. If you have a Juno of any type, next time you use it grab that little switch and operate it back and forth 10 or so times. This switch is notorious for making the audio cut in and out when dirty. And of course it’s important to keep the dust out of those sliders – put a cover over your Juno when you aren’t using it for a period and if storing it away.
Spare parts and repairs
Unless you have serious physical damage to your Juno it is unlikely to ever be unrepairable. The only thing that is liable to cause considerable damage to the 106 is an over-voltage failure in the power supply and I will address this later in the post. In the image to the left you can see an original 80017A module at the top which has had it’s black coating removed to expose the circuitry. Below it are two versions of a modern equivalent module. These new versions sound identical and have none of the problems of the original part.
One of the problem areas of the 106 that has not yet been solved is the noise issue that can develop within the chorus circuit. While the chorus has always been a little noisy the bucket brigade IC’s that produce the time delay that creates the stereo chorus effect can sometimes become worse over time and the result is a rising and falling whooshing sound that is noticeable when they chorus is turned on and the keys are not being played.
The IC’s in question are Panasonic MN3009 256 stage bucket brigade chips. They are long out of manufacture and while there are many offered on Ebay out of China I suspect that many may not be genuine so beware if you are buying them to source them from a reputable dealer. If your chorus is excessively noisy replacing one or both of the MN3009’s will almost certainly cure the problem. They are located on the jack board on the left hand underside of the top panel. I think that it is only a matter of time before someone designs a replacement assembly for these chips using a currently available part as demand for a replacement increases.
Update Dec 2019: As hoped the MN3009 IC has been reproduced this year and is available at a reasonable cost, this is great news for those who own the various Roland synths and pedals that use this delay IC.
What’s particularly relevant to this discussion about the Kiwi-106 is that by installing the upgrade you immediately improve the reliability and lifespan of the Juno because it replaces the entire CPU board and also the slave CPU on the module board thereby eliminating many old parts and of course the battery. Installation takes some careful desoldering but once it’s in it is easy to remove the Kiwi board and re-install the original parts if you want to return the Juno to it’s original state.
As you can see in some of the photos there is a high quality overlay available for the top panel from a business called Synthgraphics that shows the layout of the new control menus that the Kiwi-106 provides. This was especially good for the Juno featured in this blog post as it had a somewhat rough top panel with some surface rust and damaged paint so it made a perfect candidate for the upgrade.
Finally, a gentle warning.
In the image you can see the fracture rings on the centre and RHS legs, I forced the leg on the left down a little to better show what is going on. I remove the power supply board on every Juno that I service now and re-solder all 9 pins without exception. I find one or more pins have hairline cracks on more than a third of the Juno’s that I service. It is a quick and simple job to fix this issue and it is important preventative maintenance. I would advocate that service techs check the legs on any devices mounted to a heat sink on any vintage synth now as a standard part of servicing synths of this age. No doubt many techs already do this.
I recommend that when any Juno-106 goes in for service or for a battery or voice chip replacement or for any other issue or upgrade that you ask your tech as a part of the service that the solder joints on the heat sink mounted devices be refreshed. It’s a simple job that will extend the lifespan of the synth. it’s not something to panic about, no need for a trip to the synth doc just for this, it’s just a good idea to add it to the to-do list next time your Juno needs to be serviced.
Juno-106 buying guide and common issues
Find parts and upgrades here