Juno 106 chip revival

[flat earth]

Hmmmm............interesting, havent seen a single s/h doomed 106 since your thread!

 

 

 

 

 

 

 

 

 

 

 

we should have bought them all up before hand, could have cleared up

[McHale]

Thanks for the journey and excellent pictures. I don't have a Juno or anything (yet) that would require this kind of repair, but the knowledge is always useful down the road and we never know when it'll come in handy.

 

Great job!

 

-Mc

[ElectricPuppy]

One final update:

After removing one slider from the main control board, opening it up, cleaning it out, lubing it up, reassembling and then reinstalling it, I thought, "do I REALLY want to do this on all the rest of them? How bad are these sliders, really?"

So I went ahead an squirt a couple of drops of cleaner into all the sliders and worked them back and forth.

Big mistake.


The cleaner claims to be safe on plastics and to be designed for pot cleaning, but I discovered that it had dissolved some of the resistive tracks on some of the sliders, and killed what little grease was left in them.

That's when I said, "{censored} it" and replaced the entire board with the one from my donor Juno. That board's sliders are still in good shape, so PROBLEM SOLVED!

Final Verdict:

I have a 100% functioning Juno-106 and a sad, partially gutted Juno-106. Anyone want some parts?

The End

[elmacaco]

Name the cleaner, call that sucker out so others don't repeat that mistake!

Takig the sliders apart can be very tricky, if you put them back together wrong or too tight it can be hard to get them feeling normal again.

[ElectricPuppy]

T'was this:

http://www.mgchemicals.com/products/801b.html


Avoid.

[Gus Lozada]

It s'ez "EXTREME DANGER", anyway!

 

GOLD thread, EP!!

[ElectricPuppy]

Thank you, thank you.

Please direct all queries to the front office.

[44deluxe]

An epic thread indeed sir.

[kerryb]

Hi all,

Just found this thread - amazingly good work! Great detail, discussion, description, and documentation.

To throw out some credit: the tech Ramcur who originated this technique should be given serious thanks. When he emailed me this fix technique, I tried it and it worked so well that I had to make that video.

On the 'metal migration' concept: on one of the chips I de-capsulated, I found bits of solder between two pins on one of the OTAs. Not sure if that was something that happened during the removal process, but could also point to, among other things, that manufacturing quality wasn't tops on these chips?

And just as an update, while I've moved on to other projects and my HS-60 "tester" unit sits mostly dormant in mid-experiment, I still fire it up every few days and all voices are working cleanly and clearly. The self-osc frequency at high res is slightly off for two of the voices, but one of those that's off is the single still-encapsulated 'stock' 80017a! At some point I'll recalibrate and monitor it for a week or so.

Finally, I may do that silicone conformal coating on my opened hybrids. That seems like a good idea.

[make believe]

Great, great stuff EP!! Are these chips also covered in resin in the MKS-30? I hardly ever hear about MKS-30s failing, do they run at lower temps maybe? If anything, they should run hotter since the enclosure's much smaller...

 

 

Unfortunately the MKS-30's do have that problem. I recently had this problem with mine (dead voice chips). I spent money on a used chip, paid someone to replace it and the problem was fixed but not entirely. I told the place you had to tune all the chips after, but they claimed they knew nothing about that so I'm stuck with an MKS-30 that still doesn't work right. When I press certain keys the resonance is way out of control on them. The problem jumps around and doesn't stay to any particular keys. I have no idea how I would go about fixing this myself nor do I know people in the area willing to help. Argh. I will probably create a thread soon enough about it asking for some advice or help.

 

One of my Juno's is getting that crackling problem now so I am pretty certain after reading this thread that one of them is going. These old synths are frustrating but this thread did provide some hope at least.

 

By the way, hello to everyone.

[ElectricPuppy]

Hello, Make. Welcome!

Wild resonance that jumps around means at least one of the voice chips is either not calibrated correctly or it's going bad. It jumps around because that voice gets reassigned to new keys on every 6th unique key played.

The calibration requires a good digital volt meter and an oscilloscope, so you'll need to hand it to someone who knows what they're doing if you're not comfortable with these things.

[make believe]

Hello,

Thanks for the response. Another bad voice chip does not sound good. I'm hoping it is just a calibration issue since it wasn't doing this before they installed the chip unless the chip was bad to begin with.

Yeah I hear the calibration process is a bit tedious and like I said, I would not have any idea how to do it. Unfortunately the repair shop I go to didn't want to get involved with second hand chips so they refused to even install it. So that's when I went to this other place who installed it but claim they have no idea how to calibrate it. So now it's up to me to find a place or someone locally that can help.

[ChristianRock]

Thanks for sharing your story with the MKS-30, make_believe. I knew those things sounded too good (spec-wise) to be sold at the prices they're fetching these days. A JX3P with that wonderful Jupiter filter and good midi implementation and touch sensitivity plus more, for a couple hundred bucks? Get outta here...

Now I know...

[ElectricPuppy]

See, thing is, all the Juno/Jupes have the same IR3109 filter. The 106/MKS30 et. al just have theirs buried in an epoxy module.

[MikeD]

I recently acquired a juno 106 with a bad voice chip (just one is bad - voice 4). I like to think I'm pretty handy with a soldering iron, so I figured I'd give the acetone bath fix a go. I had a really hard time de-soldering a couple of the pins, so I decided (in my idiocy) it would be a good idea to heat up the pins and tug on the chip with a pair of needle nose pliers. Of course the corner of the chip snapped off right away with hardly any pressure [a warning to others attempting this repair - these things are FRAGILE!].

 

At any rate once I finally freed the chip and gave it a bath in acetone, the epoxy layer came off very easily even after only soaking for about 20 hours. The corner that broke off has several traces and the split goes through one of the printed resistors. (I'm still kicking myself by the way...)

 

 

So my question to the experts is, am I totally screwed, or is there some chance I can repair the traces (super glue and conductive pen perhaps?), or is it time to order up a clone / replacement chip and learn to use an oscilloscope? Speaking of which, has anyone every used one of these cheap usb / software scopes that I see on ebay? Do they actually work?

 

Thanks for any help!!

[ElectricPuppy]

I'm sorry, but I think that module is toast. You'll need a new one.

I've seen those inexpensive USB-based O-scopes, I imagine they work fine. I've got a conventional CRT-based one, myself.

[piano39]

Here's a PC Oscilloscope that is designed for audio, works through your soundcard:
http://www.zelscope.com/

I just downloaded it 2 days ago- seems to work OK. I haven't done any calibration on it yet. First impression- I have a heavy Phillips dual trace oscilloscope that I also only use for audio. Zelscope is a lot easier to use. If my first impression holds out, I will pay the shareware fee ($9.95, I think) and ebay my hardware oscilloscope.

The hardware scope does things that Zelscope can't do, but frankly, I hardly ever use those features. Conversely, Zelscope lets you print out waveforms, etc.

[Bernard]

http://www.analoguerenaissance.com/D80017/

[MikeD]

I finally received my replacement chip from analogrenaissance and installed it in my 106. It sounds so good as-is that I think I won't bother to try and calibrate it, at least for the time being. I hope the remaining original chips hang in there for a while. Thanks again for all of the help from everyone!

[p_wats]

Hey guys,

Thanks for the great thread. I've read these posts for a long time, but this one finally made me get off my butt and sign up.

I'm currently trying my first acetone soak, though it's probably a lost cause, as I snapped one of the pins taking the chip off the board (might be able to fashion a new one, but I'm doubtful). Thankfully this chip is "dead" anyway.

It's definitely takings it's sweet time though. I would encourage anyone trying it to have serious patience (I'm at a day and a half and the resin is soft, but not easily removable yet).

Woo!

[AluminumNeck]

Has anyone noticed a accumulation of yellowish tint in the acetone baths or for that matter on the boards ? I got to thinking that the whole issue may be solder flux related and that the board may have been underclenaed. As flux ages it can and often does pickup moisture and can cuase havoc in a very low current circut.

also I would stay away from varnish coatings as many of the spray on coating can and do often become hydroscopic over time. Silicone conformal is the best way to go as it is 100% non conductive.

[AluminumNeck]

the trace situation is repairable. the issue with the sand resistor is entirely different. If you knew roughly what the range of impedance was there you could build a high precision trimable circut with a potentiometer and trim it into compliane but without a base resistance thats a futile effort.

. At any rate once I finally freed the chip and gave it a bath in acetone, the epoxy layer came off very easily even after only soaking for about 20 hours. The corner that broke off has several traces and the split goes through one of the printed resistors. (I'm still kicking myself by the way...) So my question to the experts is, am I totally screwed, or is there some chance I can repair the traces (super glue and conductive pen perhaps?), or is it time to order up a clone / replacement chip and learn to use an oscilloscope? Speaking of which, has anyone every used one of these cheap usb / software scopes that I see on ebay? Do they actually work? Thanks for any help!!

[ElectricPuppy]

Yes, I did notice that there was a fair amount of flux left on the board, I washed it all off of mine with Serious Flux Remover that can't be bought anymore. And I'm almost out of it. Drat.

As for patience: Yes, you'll need it. After the first day or so, the coating should have softened enough that you can cut off the edges for the coating from around the chip, exposing the edges of the ceramic. Then drop 'em back in and let them soak some more; This should let the acetone soak in better.

[AluminumNeck]

Yes, I did notice that there was a fair amount of flux left on the board, I washed it all off of mine with Serious Flux Remover that can't be bought anymore. And I'm almost out of it. Drat. As for patience: Yes, you'll need it. After the first day or so, the coating should have softened enough that you can cut off the edges for the coating from around the chip, exposing the edges of the ceramic. Then drop 'em back in and let them soak some more; This should let the acetone soak in better.

 

 

I'd bet this whole issue is solder flux the more I sit and think about it. I don't even have it Juno but this thread cuaght my interest. I'd bet the flux is getting conductive due to moisture wicking. I have had similar issues with automotive ECU's over the years.

[ElectricPuppy]

If so, why does it only seem to affect those chips in particular? Not disagreeing, but it seems a very "targeted" effect if that's true. Seems like it should be affecting other aspects of the synth, too.