Juno 106 voice chip issues...

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Juno 106 voice chip issues...

Postby Chinagraf » Wed May 26, 2010 12:02 pm

So I got the Juno fired up after a few years in storage. I was sitting here this morning playing the start to Van Halen's Jump. I put the Juno into mono mode then when i went back to poly1 one voice started acting up, then pretty much crapped out. I did the diagnostic mode and it is chip 6, all good I can deal with that. But, chip 4 is down in level and quite dull compared to the others. Anybody know - Is this a sign that this voice chip is going bad as well or just a calibration issue?
Thanks.
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Postby chris p » Wed May 26, 2010 12:32 pm

Chinagraf wrote:I was sitting here this morning playing the start to Van Halen's Jump.


Might not the Juno simply be making an aesthetic protest?
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Postby wez » Wed May 26, 2010 12:33 pm

chris p wrote:
Chinagraf wrote:I was sitting here this morning playing the start to Van Halen's Jump.


Might not the Juno simply be making an aesthetic protest?


oh touché chris
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Postby Chinagraf » Wed May 26, 2010 12:35 pm

Bahahahaaaaaaaaaaaaaaaa
#&^% you Chris :P

(it was a good one though)

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Postby Thirteen » Wed May 26, 2010 9:27 pm

Yes, two bad chips. If you really like the synth, get a set of new clone chips and put them in, and never have to worry again. Otherwise, remove them, soak them in acetone for a couple of days to get the conformal coating off, gently resolder each of the edge pins, adding some extra solder to each, and solder a piece of fine wire to bypass the jump track on the third edge connector pin from the right to pin 15 of the IR3109 IC, and you may well be fine after that until another one goes (and it will).
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Postby Chinagraf » Thu May 27, 2010 1:34 pm

Thanks for the advice Steve. If you wouldn't mind, could you elaborate on the jump track bypass please? Is it the 3rd pin form the right of the voice chip as you look at the front, right way up? Is the IR3109 IC on the actual voice chip? I'm hunting a schemo at the moment, so maybe that will answer some of the questions.
THanks again.
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Postby Thirteen » Thu May 27, 2010 4:42 pm

The IR3109 is on the voice chip, you will see it when you get the coating off.
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Postby Chinagraf » Thu May 27, 2010 6:46 pm

Love your work.
Thanks
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Re: Juno 106 voice chip issues...

Postby tweakeasy » Sun Oct 10, 2010 11:22 pm

I have decided to undertake the Acetone method of VC recovery. I also have two dead chips (#1 and #6) and currently can't afford the Analogue Renaissance chips or to have a synth tech restore the chips for me. I've never soldered in my life and have no knowledge of electronic circuitry so I'll be going off of information on the web as to how to undertake this procedure. This will be a learning exercise for me and I'll post pictures onto a separate thread of how I go once I get my hands on some acetone (housemate has a soldering iron thankfully) and some fine wire from Jaycar or the likes.

Depending on how involved doing the two chips turns out to be (and as long as I don't solder myself to my synth (one at last!)), I may do the other 4 currently working chips as well while I'm at it, considering they're all bound to die at some stage anyway...

Andy, if you're intending to undertake the same procedure and get to it before me I'd appreciate sharing notes with you.

Thanks,

Michael
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Re: Juno 106 voice chip issues...

Postby Thirteen » Mon Oct 11, 2010 7:40 am

If you are going to use desoldering braid, the best one that I have found is the one sold by Jaycar, it's Japanese and it wicks very well. The purple coloured roll is a good size. Those spring loaded solder suckers are next to useless.
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Re: Juno 106 voice chip issues...

Postby tweakeasy » Mon Oct 11, 2010 12:37 pm

Thanks Steve, I've made a note of it. Also wanted to ask - how many days have you found to be optimum for the acetone soak and is there a danger of over-soaking them? (as in potential damage to the chip).

Thanks,

Michael
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Re: Juno 106 voice chip issues...

Postby Thirteen » Mon Oct 11, 2010 1:09 pm

There seem to be 2 different coatings - some come off fine after about 36-48 hours, some can take another 24 hours. Pull them out now and then and see.
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Re: Juno 106 voice chip issues...

Postby tweakeasy » Sun Oct 17, 2010 6:54 pm

Well I've achieved the easy lead-ups to the scary part…

• Acetone - 500ml 3M brand from Supercheap $10.95

• Desolder braid - (purple roll) from Jaycar - brand is 'Goot' 2mm $5.95

• Identified dead voice chips by running synth in diagnosis mode – chip #1 showed to be completely dead whereas #6 was just a little quieter than the rest but probably a sign that it’s on its way out so will do it too, then the remaining 4 when I have more time.

• Removed the two topmost screws at either end of the board to open up the synth

• Took photo of module board to ensure I’d plug everything back in where it goes (though it’s all pretty obvious as the plugs stay around their homes once removed)

• Carefully unplugged the 5 white connecting plugs from the module board

• Removed the 6 screws holding the module in place

• Removed module board.

Now... looking at the soldering points of the chip’s connector pins on either side I realize how delicate a job it will be removing them from the board with a soldering iron. This is a problem for me because a) the soldering iron I planned to borrow from my housemate is for medium-sized soldering and will be a bit clunky for such precise work (and I’d probably end up damaging the module board itself!) and b) my aforementioned complete lack of soldering experience… so I’ve contacted a friend who’s a wiz at circuit bending, building his own pedals and electronics in general and had previously offered his soldering skills to help me. This will be a good opportunity to learn by watching someone experienced doing it and then I’ll practice on the guts of some old hi-fi equipment I have at home and purchase my own finer soldering iron to do the remaining 4 chips.

Apologies for the essay-length entry… :D
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Re: Juno 106 voice chip issues...

Postby Futureman » Sun Oct 17, 2010 11:07 pm

Thirteen wrote:Those spring loaded solder suckers are next to useless.


I used to think so also, and swore by wick, but recently I found another brand (Spring loader solder sucker) in my stuff, and it is a killer - really awesome.
It's got me through a few jobs swiftly that wick would have taken me ages.

Cheers
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Re: Juno 106 voice chip issues...

Postby tweakeasy » Mon Oct 18, 2010 10:55 pm

So like most things desoldering the chip from the board was nothing as hard as I'd built it up to be - just very time-consuming. We used a combination of the wick and a spring-loaded solder sucker (blue anodized ones from Jaycar) and it (eventually) came out quite cleanly. The process should get a bit easier/quicker by the time I get to chip #6... but for now I'm just concentrating on #1 (the worst of the bunch) and it's soaking in acetone right now. I'm really enjoying learning these basic things and if the recovery process is a success I'll enjoy it even more! Meanwhile we're doing some perverted circuit bending of an old Casio and I'm admiring my friend's home-made spring-reverb unit which he's built into a Taylor's wine box.
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Re: Juno 106 voice chip issues...

Postby Chinagraf » Mon Oct 25, 2010 2:08 pm

Hey Michael, just saw this... I did two chips in mine but I have a desoldering station so it was easy to remove them. People with wicks usually load the pins up with solder first.
It took about 3 days for the coating to come off but some had to be peeled off, it didn't just fall off by itself. Then I used a toothbrush in acetone to clean around the finnicky .
After putting them back in I had one chip that was still a little strange, so I ordered a clone from Dnaab. AS soon as it arrived the chip in there came good and so far has behaved,
but at least I have a clone as a backup. Now would be the time to order some while the dollar is high.
Cheers.
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Re: Juno 106 voice chip issues...

Postby tweakeasy » Mon Oct 25, 2010 3:58 pm

Chinagraf wrote:Hey Michael, just saw this... I did two chips in mine but I have a desoldering station so it was easy to remove them. People with wicks usually load the pins up with solder first.
It took about 3 days for the coating to come off but some had to be peeled off, it didn't just fall off by itself. Then I used a toothbrush in acetone to clean around the finnicky .
After putting them back in I had one chip that was still a little strange, so I ordered a clone from Dnaab. AS soon as it arrived the chip in there came good and so far has behaved,
but at least I have a clone as a backup. Now would be the time to order some while the dollar is high.
Cheers.



Hi Andy, yeah it took the same length of time for me to get all the black crud off chip 1, likewise used a toothbrush dipped in acetone to get the last little hangers-on. Used a sharp edged micro-sized flathead screwdriver to do the careful lifting off before hand. Worked well. I'm giving the inside of the synth a good clean while it's open and hopefully will get to my mate's to re-solder the chip back in in the next couple of days. Will let you know how it went. Will decide from there depending on outcome if I need some clones... Hopefully not!

Cheers :)
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Re: Juno 106 voice chip issues...

Postby Thirteen » Mon Oct 25, 2010 6:53 pm

Re-flow and add solder to all of the silver pins along the base of the chip. If the chip does not work after all this, you may need to install a wire bridge across the jump track on the -15V rail if the chip batches were either 41C or 42B (I guess I should have gotten you to check the batch number before you removed the conformal coating) $-)
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Re: Juno 106 voice chip issues...

Postby tweakeasy » Mon Oct 25, 2010 7:09 pm

Thirteen wrote:Re-flow and add solder to all of the silver pins along the base of the chip. If the chip does not work after all this, you may need to install a wire bridge across the jump track on the -15V rail if the chip batches were either 41C or 42B (I guess I should have gotten you to check the batch number before you removed the conformal coating) $-)


All my chips are 40A except chip #6 which is 50B so I'm assuming that's been replaced by Roland back when they were still making them.
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Re: Juno 106 voice chip issues...

Postby tweakeasy » Mon Oct 25, 2010 11:26 pm

Just reinstalled #1 chip and it worked perfectly. So now onto #6 for the same treatment. During a Wave Form Test #5 pitched higher than the rest. Hoping that's an easy adjust by pitching it down via the corresponding trim pot, (probably not), reading about it now... Learning stuff... slowly... :(|)
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Re: Juno 106 voice chip issues...

Postby Chinagraf » Tue Oct 26, 2010 2:24 pm

Yeah you can but the pots for each voice aren't numbered sequentially. Do you have the service manual?
If not the one for voice 5 is VR 9
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Re: Juno 106 voice chip issues...

Postby tweakeasy » Tue Oct 26, 2010 6:22 pm

Nay I didn't, thanks mate!
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Re: Juno 106 voice chip issues...

Postby Thirteen » Tue Nov 02, 2010 1:01 pm

Oscillator pitch is not adjustable per voice, so I assume that you mean the VCF pitch at self oscillation, which will be a trimmer adjustment.
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Re: Juno 106 voice chip issues...

Postby Chinagraf » Wed Nov 03, 2010 11:01 am

Steve is right, that is VCF frequency. I was getting it confused with my JP-4, which you can trim the individual pitches on.
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Re: Juno 106 voice chip issues...

Postby tweakeasy » Wed Nov 03, 2010 2:12 pm

Chinagraf wrote:Steve is right, that is VCF frequency. I was getting it confused with my JP-4, which you can trim the individual pitches on.


Wish I had a JP-anything to get confused with. :P Thanks for that, duly noted. Reinstalled the second recovered chip last night, likewise worked beautifully! Spent many hours into the night tweaking in delight.
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Re: Juno 106 voice chip issues...

Postby Alastair Reynolds » Thu Dec 02, 2010 12:43 pm

Do you still need any chips ?
I don't usually read the synth page , but did today. I worked at Roland service Dept in the late 80s (even worked on Nymo's old Jupiter 8 with Midi mod on the DCE bus) . Anyway I have a number of voice chips for the old Junos that I kept for a rainy day ( all still virgin). What chips are you after ?
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Re: Juno 106 voice chip issues...

Postby tweakeasy » Thu Dec 02, 2010 6:03 pm

Alastair Reynolds wrote:Do you still need any chips ?
I don't usually read the synth page , but did today. I worked at Roland service Dept in the late 80s (even worked on Nymo's old Jupiter 8 with Midi mod on the DCE bus) . Anyway I have a number of voice chips for the old Junos that I kept for a rainy day ( all still virgin). What chips are you after ?


I'd take any as spares or for future fixes to keep my Juno alive or for other machines I pick up! PM me what you have and what you want for them and we'll work something out. :) Thanks Alastair!
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Re: Juno 106 voice chip issues...

Postby a.d.a.m. baby » Sun Dec 05, 2010 2:50 am

Alastair Reynolds wrote: I worked at Roland service Dept in the late 80s (even worked on Nymo's old Jupiter 8 with Midi mod on the DCE bus)


You mean the MD8 midi-to-DCB converter? Or was there a custom job?
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Re: Juno 106 voice chip issues...

Postby Alastair Reynolds » Mon Dec 06, 2010 12:51 pm

Nah, not an external Box. From memory (we are talking over 20 years ago) there were 2 or 3 MIDI/DIN sockets mounted on the back of the case next to the DCB socket then wired on multicolour ribbon cable down to the board. I remember it because it was the only one we'd ever seen. And of course it sounded great ;)
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