Juno 106 Resurrection

In my previous post, I mentioned that the 80017A VCA/VCF ICs in the MKS-30 will die at some point. I am expecting this because about two years ago, two of the six in my Juno 106 failed in the space of a few weeks. The 80017A is not actually an IC, it is in fact a "hybrid module" - a collection of SMD ICs and capacitors and printed resistors on a small ceramic PCB, which is then coated in epoxy. It is also notoriously unreliable. The theory goes that either some reaction occurs in the epoxy, causing it to become slightly conductive, or moisture becomes trapped inside it. One solution that many people have had success with is to remove the coating with a solvent. This seems to restore some modules to full health, but not all. Some also require rework due to poor soldering.

After my Juno expired, I removed all six 80017As, intending to give them a bath in Acetone and soldered sockets in their place to make future replacement easier. One of them had already been replaced by a previous owner and the solder pads had suffered. Then I got a Jupiter 6 and basket case Emulator II and fixing the Juno slipped down my list of projects.

Original 80017As. Two are dead and the others are on borrowed time.

On to late 2014 and having spent the last few months on a big project (to be revealed as soon as I get around to writing a post) and repairing the Emulator II (well almost, there are still some issues), I finally decided to tackle the Juno. I couldn't be bothered spending several days stripping the 80017As with no guarantee of success, so I opted for the alternative - the D80017A clones from Analogue Rennascince.

Bring on the clones!

Lots of passives.

One of the many calibration procedures.

Clones installed. Probe on one of 12 test points.

There isn't much more to write really. The clones arrived on a scored PCB panel and installation was simply a case of separating them and plugging them in to the sockets I installed earlier. An hour with a scope had everything calibrated according to Roland's original service manual and I finally have a working 106 again. Many people say the Junos are overrated as they are fairly limited, simple synths. This is true, but they do sound good.