I’ve finally got around fixing my Juno. She really did deserve it, as it turned out. I’m going to, in an accessable manner and without snobby comments (I’ve tried my best), explain the common voice chip problem of the Juno, how to recognize and fix it, as well as learn to do it all without burning the house down.
UPDATE: For a short list of symptoms, check out the update post.
I have purchased a replacement VCF/VCA chip from eBay, and, after watching a few yoga tapes and listening to Enigma, was ready to repair my Juno 106. As far as the repairs go, it really did help that Roland considered the possibility of user repairs, and has, first of all, made access to the electronics inside very easy: you just remove a couple of screws on the sides to take the ears off, and then lift the lid up – it opens up like a door (but a door on the floor; like a door to the other end of the world), as well as created a layout where everything can be easily reached. Every functional part of Juno is devided into separate PCBs – sound generating board, power board, modulation board etc.
The chips we are interested in are conveniently located on the modulation board on the left. It’s hard to miss them. There are 3 pairs of 3 chips, with the odd ones (1 and 3) of each group being the voice chips. If you’re really worried that you will screw it up and desolder the wrong thing, just read the label on the side of the chip – it should read “Roland 80017A” (Japanese for “Roland Crap Chip”).
Now, the situation I’ve had here was that one of the chips went completely silent after 10 mins of the warm up, while another one was loud. Actually, one more was kind of noisy, but I didn’t pay much attention to that at first blaming it all on the wonderful imperfect world of analogue. As it turned out after I was done with the dead chip, the noisy one started going silent as well. Need more chips.
Anyway, to find out which chip of the six was the dead one, I held the Transpose key, and powered her up. That combination of voodoo moves gets you into the testing mode. Now, once there, press both the Poly 1 and Poly 2 buttons. That fries all of the chips, so you don’t have to check which one’s dead, and just replace all six of them.
Ok, seriously though, instead of the normal unison mode, that switches on this mode where the key you hit is played by every voice consequently. So if you press the middle C, it plays it through voice 1. Press again – through voice 2 etc.
Via trial and error (by adjusting the trimmers on the board, and listening for any changes, actually), I’ve discovered that the chips are being counted from right to left. So voice #1 is the rightmost chip on the board. From there on it was quite easy. My #1 chip was the noisy one, #2 was dead, and #5 was loud. That’s ok. I got this baby pretty cheap off eBay, and I think she well deserved the attention. I bet it felt real good to be shining again after a thorough key, front panel, and insides cleaning. Almost like new now! We’re a happy couple!
Anyway.. Once you know which chip you’re hunting for, turn the Juno off, and take a picture of the modulation board at a high resolution. Now, go post it on the “Nude Junos” message board. 18+ only.
Apart from satisfying various synth perverts, the picture will be handy when reconnecting all the connectors back. Be sure to take a few pictures from different angles, because sometimes parts get obstructed by wires or a cat walking by, so you want to make sure you’ve got those scenarios covered. I, for instance, managed to pull out a wire out of a connector, and without the picture I would be uncertain as to where I pulled it out from (whenever something scary happens, I usually have an instant memory wipe; kind of like Windows).
Take the modulation board out, gaze at it, and realize the power that’s in your hands. And of course, like Tobey McGuire’s uncle said, with great power comes great responsibility. You can fix this, but you can break it even more easily. Don’t trip on your way to the desk.
Now.. Here is the part of message board posts and guides that I don’t get. All of them suggest to carefully desolder the dead chip. My question is – why the hell? I mean, the bloody thing is dead already! I gave it a try at first, but getting solder out using a vacuum sucker or a solder braid with the chip being still in the board proved to be quite tricky. The holes for the pins are tiny, and it’s pretty hard to get the solder that’s deep inside the holes out.
So save yourself some time, and just break the crippled chip off. It’ll scream a little but that’s normal; it kind of hurts to have your legs broken after all. Now desoldering the pins themselves will be much easier. Just hold the pin with a pair of tweezers, and apply heat to the solder with the iron in the other hand (the soldering iron, not the other kind). Once the pin is out, it’s pretty simple to suck the solder out with either a braid or a sucker. Your choice of guns here (I always thought “solder sucker” is a funny combination of words; it is, isn’t it? It was quite amusing to ask for those at Radioshack).
Once the holes are nice and clean , stick the new chip in and solder all the pins. Nothing special here. Just don’t sneeze or put the iron on the pillow while you go to the washroom, and you’ll be fine.
Once that’s done, check that everything is soldered properly, take the coffee cup off the PCB (how COULD you!!), and, using the pictures taken earlier as a reference, put the board back in. I don’t think it’s necessary to put the screws back. Just connect the connectors. Unless you’re 100% sure you did everything well. Then I don’t even know why you’re reading this, you’re obviously better than the rest of us.
Power the Juno up in the test mode (I personally hid behind a chair just in case it explodes; it’s ok, I do it whenever I microwave noodles or flush the toilet too), and play something. If you hear anything at all, you probably didn’t look at the reference pictures upside down, and everything is connected as it was. Now, press Poly 1 and Poly 2 at the same time again, and try the same trick. If your dead chip was like mine, it wouldn’t go silent after about 10 minutes. So give it some time while playing some chords, or just keep pressing the middle C like an ape.
If all is good, your Juno should play everything well without any drop outs. If the same thing is happening as before, you’ve either replaced the wrong chip (do you have trouble distinguishing right from left?), or you’ve got a lemon.
If it’s the former, don’t ever drive. Or you’ve tried already? They did take the license away, didn’t they. If it’s the latter though, the outcome will depend on how nice the seller you got the chip from is. If he is nice (use a lot of “please”, “thank you” and “sincerely yours” in the email when asking), he might replace it for you. In that case, you will have to desolder the chip properly; breaking it off won’t do, obviously. And if he refuses, which is a legitimate answer, since there is no way to tell if it was him or you who blew the chip, then.. Well… Think about the thousands of dollars people spend yearly in casinos. Your small $50 ($60, $100?) down the crapper isn’t a heck of a lot compared to those professional money wasters.
Hopefully, you have fixed your Juno when reaching this paragraph. Actually, you’re supposed to read through all of this beforehand. What if I said “desolder this”, and then in the end said “just kidding. Buy my book to find out how to fix the Juno you yourself have just fucked up”, huh? Don’t trust the InterMat. Or at least know whom to trust. My Juno didn’t explode, so you can probably trust me for now. Keep your eyes open nevertheless.
Oh, and put the screws back to fix the modulation board in place, eesh..