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While calibrating my Juno 106 I noticed

Posted: Thu Feb 28, 2013 6:42 am
by KennaOkoye
That my test point, near the top left of my keyboard, looks different than the tutorial Im following... Also for the sake of grounding purposes! I think my juno 106 is an early model. I don't know why it would be wired this way. Any way check it out. Any work arounds? Anyone experience this?

Image

Re: While calibrating my Juno 106 I noticed

Posted: Thu Feb 28, 2013 7:20 am
by KennaOkoye
Does this mean I don't need to connect the COM of my voltmeter, or the scope to ground?
lastly, where do I input the function generator since, the TP are buried underneath! so weird...
Thanks!

Re: While calibrating my Juno 106 I noticed

Posted: Thu Feb 28, 2013 7:22 am
by synthparts
There were 2 versions of the 106 module board, some didn't have the TP2 connector. Just put your black meter/scope lead on the ground on the board you are testing (in this case to the AG/black wire in the pic (AG is Analog Ground)).

Re: While calibrating my Juno 106 I noticed

Posted: Thu Feb 28, 2013 7:25 am
by KennaOkoye
Synthparts! thank you so much for answering this thread. Okay so do I put the hook of the black lead on the actual wire(thats soldered to the TPAG) or on the grey material that comes out of the wire (LOL). Also, then where do I connect the function generator to inject the 10vPP sine, since this is also underneath that white plug thing...

Re: While calibrating my Juno 106 I noticed

Posted: Thu Feb 28, 2013 7:41 am
by Steve Jones
Why are you injecting a 10V sine wave into your Juno?

Re: While calibrating my Juno 106 I noticed

Posted: Thu Feb 28, 2013 7:44 am
by KennaOkoye
to calibrate my chorus as stated in the service manual. chorus 2 sounds off. the first calibration was off too... Its suppose to be -15, but I got -14.60 consistently, so I calibrated it, so wanna go through and do a full cal.


Re: While calibrating my Juno 106 I noticed

Posted: Fri Mar 01, 2013 9:10 am
by KennaOkoye
Please help..

Does anyone have access to the original Juno 106 manual?? or know where the The following test point is? because I can't find Test Point 14-19 like in a normal Juno 106 module board... pulling my hair out over here on step 5 trying to do the VCF Resonance calibration. Thank you...

note: i have the module board with 2 eproms on it.Image

Re: While calibrating my Juno 106 I noticed

Posted: Fri Mar 01, 2013 9:34 am
by Steve Jones
On the earlier boards without the test point connectors you connect the probe to the leg of the trim pot itself on the hottest side of the trimmer.

Re: While calibrating my Juno 106 I noticed

Posted: Fri Mar 01, 2013 9:38 am
by KennaOkoye
steve please explain in lamens terms! thanks buddy! to the VRs? is that what you mean by trim pots?! which side is hot? how do I know that?

Re: While calibrating my Juno 106 I noticed

Posted: Fri Mar 01, 2013 9:52 am
by Steve Jones
Yes, by trim pots I mean the VR's, I haven't calibrated one of those early boards in ages but from memory you connect the scope to one side of the VR, there is a note about it I think on the First Edition Juno 106 manual. If you probe the trim pot one end of the track will have a higher signal than the other, I think that this is where Roland intend that the measurement be taken. In the way of old Roland manuals they are often a bit vague with their instructions. I would probe both sides of the trimmer on a few voices, whichever side is sitting at close to 4.8V on most voices will be the correct side unless the machine is seriously out of calibration.

Re: While calibrating my Juno 106 I noticed

Posted: Fri Mar 01, 2013 9:55 am
by Steve Jones
I went and dug out the first edition manual, the actual reference has an arrow pointing to the row of test points and a note that says: "Not provided on early PCB's: Connect to the hot terminal of trimmers defined as TP-14-TP-19". Clear as mud.

Re: While calibrating my Juno 106 I noticed

Posted: Fri Mar 01, 2013 10:08 am
by KennaOkoye
Thank you so much! this world is such a huge learning curve. thank you so much

Re: While calibrating my Juno 106 I noticed

Posted: Fri Mar 01, 2013 10:22 am
by KennaOkoye
when you do this what reading are you using? 1v or 3v resolution on the oscilliscope?

Re: While calibrating my Juno 106 I noticed

Posted: Fri Mar 01, 2013 10:46 am
by Steve Jones
Whichever resolution allows you to see the full waveform on the screen, not clipped at the top and not too tiny. Try both and see which works best for you, I would suggest 1V as 4.8V will show up fine on any standard scope.

Re: While calibrating my Juno 106 I noticed

Posted: Fri Mar 01, 2013 11:44 am
by KennaOkoye
the reason i asked is because switching from 1 or 3 changed my calibration value,... guess ill stick to 1 for everything