Circuit Overview:
A great digitally controlled 1DCO/voice 6 voice analog with patch storage and MIDI. MKS-7 is a preset rack version of sorts. The 80017A modules combine VCF and VCA for the channel. MC5534 module creates the digitally controlled waveshapes. I've never seen a diagram of one. Envelopes are also digitally generated. .
Service Tips:
One of the major sonic strengths turns out to be a slight reliability weakness. The VCF/VCA modules go out. Sometimes it's a break inside from stress so be careful when installing or removing them! Earlier machines and 41C or 42B lot numbers of the 80017A module are known to be more failure prone. I personally have seen about half of the failures otherwise be in 47A lot but that's my personal experience. (oops 2 more in a keyboard I just got in today. Over half now.) I also have a few 55A's that have gone out, a 55B, 43A and 4NA but I think most of those are usually pretty good. Take it for what it's worth of the half a dozen I've repaired or whatever. Nicely laid out with labelling on the board to figure out what is and isn't working right before the mix node.
Other than common cleaning issues and a clock buffer that died on one,...Well, I worked on one today that had a scratchy volume control. I worked it over and swapped in a new one after trying a couple other entire modules I had. ALL were fairly scratchy and it sounded anyway more like a familiar phenomena involving some kind of bad ground design. Yet Grounds seemed good. Very strange. Always bumps some at the bottom of travel and gets noisier down near it.
In the process I find there are TWO version of the bender board! And they are NOT pin compatable (portamento becomes the bender :-) ) One version has the plastic knob that matches the case. Other has more of the moog MG/opus type switch with aluminum shaft. Serial numbers were fairly close... and...it's actually the earlier synth that was having the problems of the three witht he moog type knob. Hmm. So I try swapping the jack board and sure enough the problem with the scatchy pot goes away. I'll try to research exactly *what* is causing that if I get a chance. Serial on the early one is 435534, and mine is 455827 and the one I scrapped is 494183. I see Roland only made 72000. Difference of 58,649 between those serial numbers. So...we have one of the earlier and one of the later samples there. Ok there goes number 436011 on ebay. It has the later portamento switch. So probably the moog style ones were only on the first few thousand. Also note that the early ones may have EPROM on both boards whereas they used ROM mask in CPU on the later ones after they were convinced of the stability of the product to save some money in production.
Parts:
Roland still stocks many parts for older instruments! You can always order them through your local Service Center and see what happens! Otherwise I have some parts also so don't hesitate to ask.
Contact Sound Doctorin'
12/06 GOOD NEWS!!!! I've purchased and tested one of the 40 euro module redesigns. GREAT WORK! This should drive the price of the used modules down since these are way more reliable and sound identical! Here is the Module Retro page. This device must be hard wired which takes a few minutes but well worth the effort to get something in using common 13700 ota's.
Midi Tips and a comparison of Juno-106 and Juno-60
Mike notes: I have had a few Juno106's and NEVER had aproblem with them. I always wanted a Juno 60 as they're supposed to be fatter and "punchier". I recently acquired one and so I decided to let my 106 go to someone who really wanted one. After I agreed to sell it I realized that the 106 has a higher ambience than that of the 60. Basically a string sound on the 60
with the "freq" at 10 would be equal to a "res" at 7 on the 106. The 60 didn't have the range I needed. It is fatter though as you can set the PWM of the OSC to the envelope.
The Juno-106, for it's day, was extremely well thought out. Many of the machines from the time (eg. Siel DK600 or Sequential Six Trak) were very limited in MIDI capability.
Mike continues: You should mention that the Juno Librarian (off Vintage Synth) is a realtime live editor. Meaning you have instant axcess to thousands of patches. Once saved to the Library you can recall them instantly and the saved (computer) patch will overide the 106 patch. It can them be manipulated via the computer or Juno 106 and saved. Also, you can view the parameters of that particular sound on the computer, thus allowing for easier tweeking. This is how I discovered the issue (noted above) in the first place. I set all the parameters from the computer screen to the Juno 60. The sound semmed more "muffled" like it was in a pillow case.