11 replies to this topic

[Drew 414]

I recently bought a Juno 106 off of ebay.  Seems to be fine except for one issue: it's a full step out of tune.  With key transpose function off (set to C), middle C can be swept using the tune pot on the back from A# +13 cents to B +13 cents.  That means the only note it can be set to is B.  Now of course I can key transpose it to C# so that the middle C key plays C, but that means outgoing midi data is going to be off by a half-step.  Worse, it does nothing to correct playback of incoming midi note information.  Obviously, there are workarounds, but I'd rather middle C just play middle C without issue.  Does anyone know if there is a tuning mechanism inside the keyboard that regulates the pitch information the voice chips receive from the masterclock?  I've been through the service manual, but didn't find any clear (to me) answer.  Thanks~

[Spectrum]

Interesting question, and welcome to S'Punk!



I'm no expert, and I'm hoping there's someone on here (Silverstreak, NoFi? Jester? Rusty? Luka? Somebody?) that might be (particularly if you can link us to the service manual), but I'm pretty sure there'll be some sort of tuning available within the synth.

I used to have a HS-60 (essentially the same thing, but added onboard speakers for home use, which sounded great cranked!):



I can't recall any pitch adjustment inside, but I do recall there being filter tuning for each voice, so that when jacking up the resonance towards oscillation, each voice could be set to amplify the same series of harmonics (and soon sounds ugly if each voice plays a different filter frequency, especially with all voices stacked.

Anyway, doesn't answer your question, but (hopefully) provides hope.

Let's see what the experts come up with...

[Jester_Fu]

I'm not familiar with the Juno, so i'm not going to be much help except to say track down a workshop manual for one as i'm sure there'll be an internal tuning adjustment for it. Analogue synths drift and the designs always included plenty of mechanisms to tune them in the factory and during repair.

If you're not keen on having a crack at it yourself, best to post the state/country you're in so someone may be able to suggest someone who can fix it for you.

[SilverStreak]

As far as i know theres a level, resonance and cutoff pots on the vca/vcf board. Dunno bout pitch or tuning. Do you know its history? Does it have replacement voice chips? You can normally tell by any dodgy soldering burn on the voice board pcb. You have to hit 6 different keys in an octave to hear all the voices cycle through. Continually hitting mid C will only use the 1 voice chip. Theres some instructions for calibrating your voice chips here,

http://www.synthrest...ducts.htm#JN800

Love my 106. Will love it even more when i get its sick voice replaced

[dylab]

grab the 106 voice chips here
http://analoguerenai...ce.com/D80017A/
http://analoguerenaissance.com/D5534A/

also the juno test and service procedure
http://analoguerenai...e.com/JUNOTEST/
http://analoguerenai...om/JUNOINSTALL/

[no-fi]

woah... tuning the basic pitch of the synth is very different to tuning the filter/vca chips....
:-)

I've never had to tune the pitch of a 106. but I'm also sure that there will be some basic trimmer somewhere to do it. perhaps even a trimmer cap, rather than a trimpot? don't fully know.

[SilverStreak]

^^^

Yeah but why not? while you got the lid off... Just had a look at mine, as its permanently has a fliptop lid atm. The jackboard that houses the main 'tune pot' has 3 little trimpots called vr1, vr2 and vr3. My moneys its one of those, but can't know without a look at the service manual.

[no-fi]

ok well, the first result from searching for "juno 106 service manual" in google leads to.... a page with the service manual for the juno106...
:-)

VR1,2,3 on the jack board are for chorus and what looks like overall reference adjust for the tape load input...

Anyway - there's a VR33 on the module board schematic page that claims to be for DCO CV offset. I'd play with that one first.

[Drew 414]

Yeah, the DCO CV Offset caught my eye as well.  The paragraph in the service manual on adjusting it seems to cover a lot of the "key words" I'd associate with how a DCO receives pitch information without ever actually saying what the adjustment was for.  Guess I'll crack it open and see.  It's almost certainly not a voice chip problem, and the filters and amps all seem to be in order.  A quartz crystal oscillator is manufactured to resonate at  a certain standard frequency and a (hopefully variable) intermediary should translate that into the desired CV.  Hopefully VC33 will do the trick.  Thanks for all the suggestions.  I'll let you guys know how it turns out. 

[Drew 414]

Good call no-fi.  Adjusting the VR33 pot worked.  Shame there's not one for each voice, or this would be a much cooler board.  The service manual said to adjust the VR33 trim until the test point registered at 0V.  This was giving me the A# to B range.  The range of the pot was 0V for about half of the rotation up to a maximum of ~.05V on the voltmeter.  I dialed it full on to .05V and now am getting a range of C -40 cents to C# -40 cents.  Guess I could dial it in a little more perfectly, but can't think of any good reason to.  Seems like a lot of drift, but it's a 25 year old crystal and I guess I really have no idea what amount of clock drift might translate into a significant tuning change. So much for DCO stability.  Still, you'd think others would have had this problem if it only took a relatively small drift, and you'd hear reports of temperature tuning issues, as well.  Could be mine was just crap to start with.  In any case, fixed for now and hopefully it'll stay that way.  Thanks again for the help.

Edit: Worth noting for anyone else who might encounter this issue that the multimeter really isn't necessary since it's not a specific voltage you're aiming for, but whatever position allows you to get the DCOs back in tune.  Just turn the pot until you find what you're looking for.  You should still, ofc, enter test mode, and reset the D/A to output 0V with the MIDI CH key as indicated in the service guide prior to doing so.

[ehsan]

Hmm. Though, there's 'so much for DCO stability' as in you turn it on and it stays in relative tune if not absolute, and there's turn it on and keep flattening your notes for the next 15 minutes a la VCO.

ie. Quit ya whingin!

;D

[Drew 414]

Aye, but if it drifts another 60 cents south, it's permanently out of tune (well... at least until I can find a replacement crystal).  Would be quite funny if 5-10 years from now everyones Roland DCO boards were a step or two sharp.  But, you're right, I can always transpose the keyboard, or tune the joystick to make the adjustment and pin it down with duct tape if I'm controlling it stacked with another keyboard.  Pure analogues certainly can have much worse tuning issues so yeah... I'll survive.