Roland JUNO-106/HS-60-1984    Weight=22 Lbs. Number mfg.=72,000 MRP=$1095

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. Not sure what's inside the dco module. 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. (Those were the numbers specifically mentioned in Roland's 1984 service bulletin saying replacement was the only option. Perhaps on some of those this was true but more recently we've discovered that softening the covering in acetone and just removing it after a day or two of soaking will repair a large percentage of faulty modules! It turns out a lot of problems were being caused by conductive crystals growing inside of the protective jacket it appears!) 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.) In 2017 I did a unit with 53A's and all but 1 had an issue before I was done. 1 was broken in the mail and one had a wire come off when I removed covering. 2 failed and didn't respond to removal of covering. ) I also have a few 55A's that have gone out, a 55B, 43A and 4NA (x2 now) 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.
     An issue of output distortion I see attributed to damaged mute transistors. Marc Marc says C45, C44, TR21, TR22, TR23 can all just be pulled if you don't mind some pop at turn on in JUNO 6 or 60. Verify equiv. parts in 106 schemo.
     Other than common cleaning issues and a clock buffer that died on a couple, and one that had that and IC8 fail leading to a couple 8 note segments not responding AND a R/W line from memory chip where the trace failed (and saw someone else also had this issue the same week!) AND a 4.99k resistor go open making the VCF levels all change very little causing no sound to pass in the amp that is supposed to amplify instead of attenuate that signal :-) (poor guy from Indonesia sent it all the way here and it ate so many hours after the modules all failed... to get compensated I'd have to charge 450.00 or something at this point!! w/4 of my modules =240.00 plus more time than that....)
     ...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 made 72000. Mine has the later portamento switch and I'm looking at a unit 421646 which has earlier switch design AND has the pale green number buttons rather than the blue ones I have on mine. In another picture I see same on those two features. 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. (PS Here is a table of Roland Serial number prefixes (first two digits til 1989 some month I believe)
     HS-60 for synthark had missing module on voice 5/6 which oddly gave noise only w/ 1-4 doing nothing. Installing one 5/6 work...no 1-4. You'd think it was op amp as it's common to 1-4 and other things 4051 mux handles were fine. Oh and one channel..2 i think would drone due to oscillation which persisted w/ op amp removed from socket i installed. New 4051 fixed it.