Members AluminumNeck Posted May 19, 2009 Members Share Posted May 19, 2009 I'd bet this is a heat issue. 99% of electronics fialures are. Link to comment Share on other sites More sharing options...
Members DINpluggedIN Posted May 19, 2009 Members Share Posted May 19, 2009 I'd bet this is a heat issue. 99% of electronics fialures are. There have been plenty of glue/adhesive and encapsulant problems that have led to failure of electronic circuitry. One possibility is that the material can change in nature over time (heat sometimes being the causative factor), becoming hygroscopic. Link to comment Share on other sites More sharing options...
Members ElectricPuppy Posted May 19, 2009 Author Members Share Posted May 19, 2009 The acetone is doing it's thing, but very slowly. I could get a few chips of resin off around the edges, but clearly it needs more time. ...Sigh. Link to comment Share on other sites More sharing options...
Members Numina Posted May 19, 2009 Members Share Posted May 19, 2009 Curious - what are the symptoms of a faulty chip? Link to comment Share on other sites More sharing options...
Members ElectricPuppy Posted May 19, 2009 Author Members Share Posted May 19, 2009 Curious - what are the symptoms of a faulty chip? It seems to vary. In my case across 3 chips I've seen: - Voice goes entirely dead;- Static / crackling with changes in volume;- Drifting / wavering resonance; There's probably other symptoms as well. The problem chip contains the VCF and the VCA, so just about any way you can imagine those signals paths as failing is what you'll hear. Additionally, I had not one but 2 of the DCO chips fail, as well. In my case, the sub osc on both cut out completely. If I can get the resin off of this chip and if it appears to fix it, then I'm planning to yank ALL of the chips (the 5 other VCF/VCA and all 3 oscillators) and treat them similarly. Link to comment Share on other sites More sharing options...
Members ElectricPuppy Posted May 19, 2009 Author Members Share Posted May 19, 2009 Beyond this, I've got 3 other things I could take of, I'm open to suggestions: - The foam "modesty" cover around the portamento toggle disintegrated. I'm thinking of cutting out a new one from black felt.- The sliders need cleaning. I'm gonna just blast the crap out of them with WD-40.- The blue buttons have faded to a kind of grayish-green... I don't think there's anything I can do about that, but it bugs me that they don't match the blue paint anymore. I have a donor I can experiment with, I'm thinking maybe a light hit with some sandpaper, or maybe some kind of light rubbing with solvent might be a way to "exfoliate" them... thoughts? (I'm kidding about the WD-40. What's the general concensus on an appropriate cleaner for sliders?) Link to comment Share on other sites More sharing options...
Members ElectricPuppy Posted May 19, 2009 Author Members Share Posted May 19, 2009 ...oh and I need to replace the group select button, it's gotten a bit touchy. ...and I'd like a ham sammich, if someone wouldn't mind delivering. Link to comment Share on other sites More sharing options...
Members ChristianRock Posted May 19, 2009 Members Share Posted May 19, 2009 Link to comment Share on other sites More sharing options...
Members ElectricPuppy Posted May 19, 2009 Author Members Share Posted May 19, 2009 Gracias! Link to comment Share on other sites More sharing options...
Members kpatz Posted May 19, 2009 Members Share Posted May 19, 2009 It seems to vary. In my case across 3 chips I've seen: - Voice goes entirely dead; - Static / crackling with changes in volume; - Drifting / wavering resonance; Voices sticking "on" or a ghost voice lingering when the VCA is supposed to be completely cut off are common symptoms of a dying chip as well. "Drifting/wavering resonance" would technically be "drifting/wavering cutoff", but it's most apparent when resonance is in self oscillation. EP, I think there's some kind of slider cleaner/lubricant you can use, I'm not sure what it's called. As for the faded buttons, maybe you could just paint them blue? P.S. A spritz of contact cleaner sprayed into the membrane switches should help your buttons to work better too. P.P.S. On one 106 I restored, the felt around the sliders/switches was disintegrating. I simply removed it and left it off. The 106 looks fine without it. For the portamento switch you could use a piece of felt or even a piece of black paper. P.P.P.S. Someone had to post a ham sammich on a day I didn't have time for lunch... Link to comment Share on other sites More sharing options...
Members kpatz Posted May 19, 2009 Members Share Posted May 19, 2009 I'd put the 250$ for a set of clones and make a reliable 106 I can use for decades more (hopefully) Think about it - I can play mine live without being worried about faulty ICs Until the DCO chips start to die, and AFAIK no one is cloning those yet. Link to comment Share on other sites More sharing options...
Members xpander Posted May 19, 2009 Members Share Posted May 19, 2009 he is already plotting his revenge on your voice chips: Link to comment Share on other sites More sharing options...
Members urbanscallywag Posted May 20, 2009 Members Share Posted May 20, 2009 I'd bet this is a heat issue. 99% of electronics fialures are. I still find it hard to believe. Take an LM13700 for example. 1.3mA per channel, max of 36V rails. Say 6 OTAs (4 for filter, 1 for resonance, 1 for VCA). P = chan * V * IP = 6 * 36 * 1.3mP = 0.2808 W A quarter watt max, and I don't think the Juno uses +/- 18V rails nor do I think they use the max supply current. So maybe 100mW. I suppose over 27 years it could be... Link to comment Share on other sites More sharing options...
Members ElectricPuppy Posted May 20, 2009 Author Members Share Posted May 20, 2009 The resin has lifted. There are three SMD chips mounted to a printed circuit on a ceramic substrate with a few printed resistors and a couple of tiny SMD caps. There's still a few pieces of resin stuck between IC pins, so I'm letting it soak until tomorrow to make it easier to pick out the rest of it. Wheee! Who wants to know what the chip designations are? Link to comment Share on other sites More sharing options...
Members xpander Posted May 20, 2009 Members Share Posted May 20, 2009 post pix foolio! Link to comment Share on other sites More sharing options...
Members urbanscallywag Posted May 20, 2009 Members Share Posted May 20, 2009 Who wants to know what the chip designations are? Done the 'elegant' way. http://homepage.mac.com/nicksdsu/80017a.jpg http://homepage.mac.com/nicksdsu/80017a-ic.jpg There's a IR3109 (that's the number right?) in there too. Link to comment Share on other sites More sharing options...
Members ElectricPuppy Posted May 20, 2009 Author Members Share Posted May 20, 2009 Done the 'elegant' way. So sad. Yes, it's an IR3109. Link to comment Share on other sites More sharing options...
Members ElectricPuppy Posted May 20, 2009 Author Members Share Posted May 20, 2009 Not much update this morning, kinda rushed for time. There's lots of little bits of resin to pick out, it's a bit like cleaning teeth. I've got a large needle I used to get some of the bits out between IC legs, will probably take me a good 20 minutes to dig it all out. The back of the ceramic still has a large section of resin on it, but there's no traces on the back side so I'm less concerned about removing it. 2x BA662F1x IR3109N4x itty-bitty capsa handful of printed resistors I need to look at the sparse drawing of the module in the service manual and see if if a more detailed schematic would be worth drawing up. Link to comment Share on other sites More sharing options...
Members ElectricPuppy Posted May 21, 2009 Author Members Share Posted May 21, 2009 Alrighty, some pics and commentary! Here's the main board, nothing really exciting to note here, this isn't the first time I've had it out. Remove 6 screws, yank about 5 cables and voila! Here is the problem module removed. At the time it was removed, it was exhibiting static and crackling with random changes in voice volume. (This is voice channel 1.) Some sharp-eye'd folks might ask, "what's with the aluminum standoffs and screws?" When I have the board flipped over for soldering, I don't to be putting any pressure to the other modules, which are the tallest things on the board. These standoffs are just temporary work feet. Behold our Instruments of Judgement: a glass container and some acetone. Diet Pepsi is optional. Into the pits of solvent hell, foul module! I let it soak for a day, scraped off softened edges to let solvent get underneath, and then soaked again. 3 days total, and then it started to lift off on its own: Behold! Here it is before I gave it a detailed going-over. Notice how the component side resin came off as almost a complete sheet; that made life easier. The back side, though, was being more stubborn. And now the shot you've all been waiting for, at high res. Notice the cool multilayer circuit printing on the ceramic. I see a bottom trace layer, an insulating layer, another trace layer, some printed resistors (the variously sized dark gray rectangles) and the solder mask. Pretty neat stuff. There's some little black "blobs" here and there, mainly near the resistors; I don't know what they are, and they haven't softened like the resin. I'm leaving them there. On the back side, the resin is still be stubborn. There's no circuitry on the back, so I'll just leave that resin be. Here's the module reinstalled and ready to go back into the Juno. Sorry, Mister Blurry Cam stole the camera from me and took this, not my fault: Results: On power up, no magic smoke appeared. I count that as a Big Plus! For extra bonus points, though, the voice worked again! No crackling, no popping, no weirdness of any kind! YAY!! I let it run for 20 minutes to get good and warm and it was solid the whole time. However, by then voice 4 had had enough and gave up entirely. So, once I get some more solder wick (I'm out), I'll yank that module and give it the same treatment! Questions? Link to comment Share on other sites More sharing options...
Members kazper Posted May 21, 2009 Members Share Posted May 21, 2009 Do you have a LCR? I'd be curious if there is a capacitance on the epoxy. Your almost there, change out those Green Films and the electrolytic and you almost have a new synth. Link to comment Share on other sites More sharing options...
Members ElectricPuppy Posted May 21, 2009 Author Members Share Posted May 21, 2009 Do you have a LCR? I'd be curious if there is a capacitance on the epoxy. Your almost there, change out those Green Films and the electrolytic and you almost have a new synth. I don't have a conventional LCR tester, but there's a cap test function on my DVM, that might show something interesting. Could check for abnormal conductivity too, didn't think to try. Link to comment Share on other sites More sharing options...
Gus Lozada Posted May 21, 2009 Share Posted May 21, 2009 This thread is gold.Thanks Mr. Puppy, E. Puppy. Link to comment Share on other sites More sharing options...
Members flat earth Posted May 21, 2009 Members Share Posted May 21, 2009 Great work Pup I didn't realise the modules just pulled out. Always thought they were soldered in. I also wondered why Roland saw fit to encase them in resin in the first place Link to comment Share on other sites More sharing options...
Members gilwe Posted May 21, 2009 Members Share Posted May 21, 2009 That's info really ! Good to know you can now just "fix" these 80017A chips ! Link to comment Share on other sites More sharing options...
Members TropicThink Posted May 21, 2009 Members Share Posted May 21, 2009 I'm with Gus, Flat Earth and Gilwe, Electric. This thread absolutely rocks. Big time. Great work, bud. Link to comment Share on other sites More sharing options...
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