A couple of days ago I bought a used Roland Juno Alpha 2 off Ebay for a really great price. It had numerous problems, but I felt I could fix it and I’m happy to report that the Roland Juno 2 is in perfect working order now. Below are some notes about what was wrong with the Roland Juno 2 and the steps I took to correct the issues. At a glance, some of the issues were a broken joystick and bender/pitch wheel, a check battery message, a couple of dead keys, and an extremely dirty synth inside and out. I also was not sure if the output jacks, chorus, and membrane buttons were all working yet. This was a gamble purchase, but I felt the problems would hopefully be fixable.
First the Roland Juno 2 was in absolute filthy condition. I think this synth had the most dirt, grime, dust, and just about everything you can think of tucked away inside. It had never been opened and when I lifted the lid off the top of the synth I couldn’t believe it was still in operation. It took me about two hours to clean all the stuff out of it and check all the wiring to make sure everything was stable and connected properly. Once the Juno 2 was cleaned, I proceeded to change the battery.
Changing the battery proved to be much easier than expected with the exception that you have to lift out the key bed before you can slide out the CPU board with the battery connected to it. Be careful when doing this because the cpu is connected to a couple of slots under the key bed and you don’t want to yank it out and rip off an electronic component on the CPU board. Just be gentle and it will gradually slide out. The battery was soldered to the main board as expected, but unlike other synths I was actually able to solder a battery holder directly to the main board due to excellent pin hole spacing. I usually use wire leads but in this case my spare battery holders were an easy fit. I then popped a fresh battery in and later reset the Juno 2 in order to remove the “Check Battery” message.
Note you MUST reset the Roland Juno 2 after a battery replacement in order to clear out the error message “Check Battery”. This was a big problem I found a lot of people had around the web. Another important note is that I’ve seen quite a few Juno 2’s with leaky batteries. Be careful not to buy one with battery crap all over the CPU as that will likely give you a giant headache trying to repair the CPU board if that’s at all possible. I had a teeny tiny bit of leakage with my old battery and I felt extremely lucky I caught it in time. With the battery tucked under the Key bed, it will be IMPOSSIBLE to see by just opening the top cover. You may be able to poke a flash light on the side, but that’ll be tough. Be careful about leaky batteries!!
With the battery in operation, I then reloaded the factory “memory” presets into the Roland Juno 2 using my Mac iBook and Sysex Librarian. I found the Juno 2 factory sounds in sysex format in the Juno Yahoo Groups. They are easy to find there and everything loaded up just fine. Be sure to follow the instructions in the Juno Factory Kit because you must press the WRITE key at the same time as the DATA TRANSFER and BULK LOAD keys in order to transfer the factory patches from the computer to the Juno 2.
Fixing the Roland Juno 2 dead keys was pretty easy. You have to remove the key bed which is far easier than most keyboards. Then you have to turn it over and lift up the plastic strip locking the key in place. From there you can lift out the dead key pretty quickly. Under the silicon rubber piece you need to gently clean the carbon contacts with alcohol cleaner. I usually rub generously with a Q-tip until I see a light black color on the Q-tip. I stopped using the rubber eraser trick because it has failed every time with me. I have had almost 100% success with using a pure alcohol cleaner and rubbing gently with a Q-tip. Later when the keys were tested, all of the dead ones were brought back to life. The keys were fixed!!
Finally, I had to tackle the big problem of the broken joystick/pitch bend wheel. There were three things I had to do in order to fix this problem and it’s very important that you check each one.
1. Probably the most important, you need to twist the middle metal shaft with a screw driver so that the center line is “vertical” and not horizontal. In every case when the center shaft line set to horizontal, I got absolutely no pitch bend effect. Once I twisted it vertically, I got my pitch effect and modulation settings back.
2. You MUST make sure that the tiny allen screw at the bottom of the plastic pitch bend wheel is securely tightened. This is critical and leads to most problems found on a broken joystick. The allen screw is what secures the joystick to the center metal shaft. If this comes loose, the spring will become unstable and thus you’ll get an unstable joystick which likely will either not work or give you crazy results. I often read reports about goofy joysticks in the Roland Juno 2 and likely that’s because the allen screw is loose at the bottom. This a precision joystick and you MUST have everything tightly secured and in it’s proper place.
3. There are at least six contact points on the pitch bend wheel. You should clean those with contact cleaner to ensure proper flow of signals reach to and from the Roland Juno 2 CPU board. I dismantled the entire pitch bend wheel and cleaned everything which I’m sure helped in bringing the pitch bend wheel back to life.
One more note about the joystick. With mine, the top vertical stick part had broken off likely by someone who whacked the joystick against something when they weren’t looking. I can say that even with the vertical stick part broken off, the Joystick is 100% usable. Of course you can either replace the joystick plastic part with another spare from another keyboard or you can simply epoxy a stick on top if you like. The semi-circle portion of the joystick sticks out plenty to toggle the joystick with your finger or thumb. It might even be easier for you. The indentation where the stick broke off also offers a good way to grip the joystick and toggle it from side to side as well.
Modulation is easy by simply pressing the wheel forward. Unless you plan to resell a completely original Roland Juno 2, I wouldn’t hesitate at all buying a Roland Juno 2 with a broken Joystick. They are SUPER simple to fix and I now know that most problems are a result of one or several of points above not being addressed properly. Also note that the center metal shaft on the joystick is “ROUND” and not “SEMI ROUND” like on some other joysticks. I pulled one from a used Roland XP-10 for example and while it will work fine as a replacement, you will need to cut out a circular hole rather than use it’s SEMI Circle hole. Other than that, most any joystick could probably be put into the Roland JUno 2 with some slight modification.
After putting everything back together on the Roland Juno 2 I tested the chorus and membrane buttons and all worked. I now had a totally 100% working Roland Juno 2 Synthesizer. Hurray!!
The Roland Juno 2 is a pretty sweet synth. I also have the Roland MKS-50 and both are a joy to use. The Roland Alpha Juno 2 is probably the easiest synth I’ve ever repaired and if I ever found another broken one for cheap I would grab it instantly. A LOT of people have problems with this synth I found while researching the web and while it stumped me a bit with a few things, once I figured out the fix it was downhill from there. Do check out the Roland Juno 2 as it’s a very nice cheap analog synthesizer that sounds simply wonderful.
Here is a nice demo of the Roland Alpha 2 on YouTube by RetroSound.
Jim Atwood in Japan 
Jim,
Thank you for the detailed information for repairing Alpha Juno 2. Those vintage synths should deserve more respect! I didn’t know that Alpha Juno 2 had velocity AND after touch sensitive keyboard. How’s the feel of the keyboard, is it decent? I love fixing electronics as well (although I’m not that good at it), so I love posts like this.
Hello and thanks for the comment! Yes, the Roland Juno 2 has both velocity and after touch sensitivity. I’ve read that many believe that the feel of the keyboard is better on the Juno 2 than the Juno 1. Personally, I really like the feel of the Juno 2 keyboard. In fact they are semi-weighted as when you turn it over there are weights epoxied onto the bottom of the plastic keys. This alarmed me a tiny bit because I had recently finished a project with a Roland XP-80 that had bad epoxy. It melted and all of the metal weights fell off. So, for a brief moment I wondered if the Juno 2 would do the same, but I later found out that the XP-80 epoxy case was an isolated one with only a few select models if correct.
The Roland Juno 2 is also smaller than most synths. My Juno-60 looks huge next to the Juno 2 and it’s even smaller than the JP-8000. Thus if you are looking for a synth with a small footprint, the Juno 2 is pretty cool. However, the Juno 2 is a bit heavy because of the metal bottom. The top part is plastic with membrane and plastic buttons. I really like how easy it is to adjust the mod depth/type, brilliance, and env time easily on the top of the synth. Plus the chord memory and portamento functions are fantastic. I grew up in the 80’s and early 90’s when early Techno and Rave was big with 2 Unlimited, LA Style, etc. and the Roland Juno 2 really reminds of this period of music.
The Roland Juno 2 is about as RAW as it gets with synthesizers. It’s really gritty and untamed which really is different sounding to me. I really can’t believe people are selling these for so cheap. I highly recommend one if you see one for sell in your area. I don’t thin you’ll be disappointed. I have enjoyed my Roland MKS-50 which is the rack version, but the Roland Juno 2 is a different approach with the keys, alpha dial, and other functions at your fingertips. It’s great to have both!
Thanks again! Have a great weekend! – Jim
Hi Jim!
Alpha Juno is perfect synth for electronic dance music. Italo disco, house, techno, acid, rave, d’n’b, trance, synth pop… everything goes. Very easy to program, GREAT sounding synth and still quite cheap. Who needs hundreds of knobs? 😀 My Alpha Juno had broken bender unit. Now it’s working like new. Thanks Jim!
Just picked up a second Roland Juno 2 off Ebay for a great price. There were ten broken keys, but I suspect they just need some contact cleaning. Other than that, it’s likely to be another Juno 2 in perfect working order. Dual Juno 2 Synths!!
Another important thing to do when you receive a broken or funny Roland Juno 2 is to do a factory reset. The second one I just purchased has some strange hanging noises and overall settings seemed tampered with. I initialized everything and now it’s operates 100%.
Here’s the factory rest procedure for the Roland Juno 2:
1) The Alpha Juno 2 must be powered off.
2) The Memory Protect switch must be off.
3) While holding down the PORTAMENTO and DATA TRANSFER buttons, turn on the power.
4) Release the buttons.
5) The display will show something like “Initlz Funct RAM”
6) Turn the power off.
7) Turn the power on.
Note that the above procedure will replace any settings saved under TUNE/FUNCTION and MIDI with the factory original settings. In addition the “Check Battery” message will disappear after a successful battery replacement.
Hi Everyone
I have a special problem with the Roland Juno 2 that has 10 dead keys. There
seems to be a pattern where two keys side by side are dead. Thus 5 sets of two
adjacent keys spread across the keyboard. I also feel there likely is a
pattern, but I haven’t had time to determine that yet.
I was curious if anyone has had experience fixing dead keys that are not silicon
rubber or carbon contact related. I feel this is a different issue as I have
fixed many synth keys using the methods described with cleaning contacts. Note
I did try cleaning the contacts and nothing fixed the problem.
I will be completely dismantling the keybed and will look for either trace
cracks or broken wires. Something is amiss for sure and I’m a bit stumped.
Thanks for any ideas.
Jim
One thing I realized is that I already have another 100% working Roland Juno 2
in my studio. I figured I would swap the keybeds and see what happens. If the
keybed works 100% in the faulty Juno 2, then I would likely know that the
previous keybed was indeed bad. If when I swap out the keybed it has the same
key issues, then I’ll know it’s either a wiring, diode, or chip problem on the
main board perhaps. That might also be a good way to test things. I’ll check
that out and report back later.
Here’s an update when swapping keybeds with a perfect working Juno 2 and the
newly acquired faulty one.
1. I put the keybed from the 2nd “faulty” Juno 2 into my 100% working Juno 2.
The exact same keys were dead, thus I am now certain that the problem exists on
the keybed and not on the main board. Now I know the keybed is the problem.
2. The dead keys are as follows from the left most key. I believe the lower
keybed starts at C1.
Dead keys are ….
E1, F1, C2, Db2, Ab2, A2
E3, F3, C4, Db4
All other keys work perfectly. Also note that the dead keys are 100% not
working. Even if I play harder, nothing comes out.
My next step probably will be to completely strip the faulty keybed and examine
all of the rubber, contacts, wires, traces, and diodes.
Time consuming perhaps, I don’t know, but at least I’m confident the keybed is
the problem and not the main board.
Another note is that when I midi in an external keyboard controller, all
functions work perfectly on the faulty Juno 2 synth. It’s sounds fantastic,
even the chorus. It’s 100% in working order with the exception of the 10 dead
keys on the keybed.
I feel I’m closer to the problem and I’ll update you on my progress shortly.
I think I “may” have found the root of my problem. Here are two links to images
I shot of the Roland Juno 2 keybed PCB board with the keys and rubber pieces
removed.
I used photoshop to indicate the dead key contact areas along with “yellow” and
“red” lines that connect them. I found that from the orange/red wire connector
on the right ( see image 2 ) the yellow and red lines connect ALL of the dead
keys on lines 3/4 and 21/22. NOTHING to the right of the orange/red wire
connector is affected. Only all keys to the left.
This leads me to believe there is a problem between the orange/red wire
connector and the first dead key set which is C4 and Db4. It’s like a power
source or something from the red/orange connector. As you will notice on the
image, there looks to be a trace issue possibly right before the Db4 contact
indicated by a light blue line. This trace is in red and connects 22 to 3 if
correct. The traces to the right on both yellow and red lines look ok.
Unfortunately I don’t have the proper tools handy here to test that connection,
but I’m wondering if I solder in a jumper wire if that might be good enough for
testing. My initial guess is that nothing is getting through from the
red/orange connector to that row of key contacts. It makes sense to me that
this could be the main problem and why the sets E1/F1, C2/Db3, Ab2/A2, E3/F3,
and C4/Db4 all don’t work.
OR.. the two wires on the red/orange connector are messed up. I’ll check those
too.
Hopefully the images and the details I posted here make sense. I think I’m very
close!
I’m happy to report that the Juno 2 is completely fixed!!
I had to solder a jumper wire connecting both the red and yellow lines at the
blue area I indicated on the images. I tried the red connection first and that
brought back 5 keys. I then went back inside and connected the yellow which
brought back the remaining five keys.
It makes sense because the two black lines right above each other were both bad
so something must have gotten in there and messed up those traces. The Juno 2
keys all sound great now. I played it for about an hour without a single hiccup
so other than some further cleaning I think I’m good to go.
Thanks for a great resource. I’m picking up a Juno2 tomorrow with the various dead keys in the lower octaves, works fine via MIDI, so I suspect the same issue with dead traces as you described. Would you be able to post how your jumpers look after repair? Did you go from point to point (between key solder contacts) or directly to either side of the broken trace itself?
In case anyone is looking for it, you can download the Roland Juno 2 service manual here: http://www.synfo.nl/servicemanuals/Roland/JUNO-2_SERVICE_NOTES.pdf
I have an old Roland Alpha Juno 2 in my garage! Anyone interested in buying it?
I just picked one of these up for ¥5,000 in a used shop. It was really, really dirty but I’ve managed to clean it up nicely. Also, the battery is dead in mine. I have zero electronics experience and I’m wondering how easy it is to change the battery for a non-techie person like me. I’m kind of hesitant to take the lid off, but for now it’s just a preset machine.
I have a very odd problem that i cannot figure out maybe someone can help me. I recently bought a Roland Alpha Juno-2 at goodwill of all places. I found that when I have Chord memory turned off (the light is off) I have a pattern of C1, Gb1, E2, C3, Gb3, E4, C5, & Gb5, (basically every other C Gb and E) all these notes play a horrific chord. I know how to write to chord memory and such but I cant change these notes to play as their true respective note. It is very annoying because i cannot just play a simple chord with any of these notes without it only playing the nasty chord designated to each of these keys. I’m very new to synths, is there anything i can do or is it some sort of defect, i feel like there has to be a solution because the defective notes are in such a distinct pattern.
Thanks in advance!
Hi Kevin,
My initial advice would be to check the battery and do a factory restore of the Juno 2. You can check inside to see if the battery is still soldered to the main board. If so, then it’s just a matter of short time that it will likely act up and need to be replaced. All sorts of crazy things can happen with a battery on the way out. The factory restore procedure is as follows:
1) The Alpha Juno 2 must be powered off.
2) The Memory Protect switch must be off.
3) While holding down the PORTAMENTO and DATA TRANSFER buttons, turn on the power.
4) Release the buttons.
5) The display will show something like “Initlz Funct RAM”
6) Turn the power off.
7) Turn the power on.
The Factory restore “may” be all you need to do. Ruling out the battery and factory restore will then give you an idea if the problem might be in the hardware. Please let us know how it works out for you.
Jim
I have an alpha juno 2 and since I got it the keyboard never worked at all – I’ve only played it from another midi keyboard. Now that other keyboard is broken and I have no way to play the alpha juno 2 now, so I thought I would have another go at investigating why the keyboard doesn’t work. I’ve opened it up, examined all the internal connections, and everything looks OK. Do you guys have any ideas?
BIG thanks for the factory reset tip! My Juno 2 had a problem of having no velocity sensitivity. Once I discovered that after midi dump velocity started to work misaculously but after turning it off and on the sensitivity was lost again. But after following the factory reset advice velocity now works full time, plus an annoying startup message ‘check battery’ has cleared up (battery was changed). Great little synth!
BTW, I’ll add another tip. Some of my Juno’s keys did not work when I bought it. I cleaned the contacts with alcohol but that helped only partially. Then I discovered that the rubber contact strips of the keys are exactly the same ones that a Roland’s cheap old midi keyboard PC-200mk2 uses. I had one laying around and replaced my Juno’s rubber contacts and voila – all the keys work now!
I haven’t only managed to get the aftertouch to work.. any advice on that?
Hi Jim!,
Great article! I have owned a Juno 1 since it was introduced and recently began rediscovering it from my new interest in ambient music. Such a great little machine! After all these years I have not got a Check Battery message but I looked at it anyway and it is not leaking either, believe it or not! But thanks to you I will know how to fix it in the future!
Question: Do you know if the reset procedure is the same for the Juno 1 as the Juno 2?
Thanks again!
Hi, I am a proud owner of a HS-80 and spent the past 24 hours banging my head against a wall trying to figure out how to do a RAM initialization. Of course, I tried the procedure for the alpha Juno 2, but had no luck. Then I went through the list of roland rom reset combos and tried to see if another model’s instructions worked on the HS-80. No luck.
There are websites that list the reset procedures for Roland models, and they all said “HS-80: no rom reset”. I knew this couldn’t be true, so in the absence of a service manual I just tried random button combinations and … I figured it out!
Please pass this info onto anyone that will find it useful.
RAM Init
1) The HS-80 must be powered off.
2) The Memory Protect switch must be off.
3) While holding down the BRILLIANCE and DATA TRANSFER buttons, turn on the power.
4) Release the buttons.
5) The display will show something like “Initlz Funct RAM”
6) Turn the power off.
7) Turn the power on.
Version Check
1) The HS-80 must be powered off.
2) The Memory Protect switch must be off.
3) While holding down the MOD RATE and BRILLIANCE buttons, turn on the power.
4) Release the buttons.
5) The display will show something like “Ver 4.6h 3.19 86”
6) Turn the power off.
7) Turn the power on.
Copy Preset Bank to Memory Bank
1) The HS-80 must be powered off.
2) The Memory Protect switch must be off.
3) While holding down the BRILLIANCE and KEY TRANSPOSE buttons, turn on the power.
4) Release the buttons.
5) The display will show something like “Copy Preset to Memory”
6) Turn the power off.
7) Turn the power on.
These are the only functions I have found.
Thanks for the above list, it helped me find the version check for the Juno-2 which appears to be on PORTAMENTO + MOD RATE. On my machine it’s “Ver 4.3 2.12 86”. RAM INIT and Copy Presets to Memory are listed in the service manual, but not the version check for some reason.
Hello Jim,
Is there a vendor that you would recommend for replacement benders for the Alpha Junos? I’m going to look at an Alpha Juno this weekend. And it appears the bender spring has broken.
Cheers, Jared
Hello Jim! After reading this page this weekend I opened my Juno 2 and checked. Leaking electrolytic capacitors, weak battery.. Now I’m writing a list of parts. Ty for all information!
John
I just bought an Alpha 2 off ebay for a decent price. I was wondering if you could post info, on the battery swap, Jim? Particularly the holder part you used. I would like change the battery ASAP, but I want to have the parts ready when I open it up. Thank you for a wonderful resource.
Alpha Juno / MKS-50 / HS-10 / HS-80 battery swap and parts info here;
http://www.llamamusic.com/mks50/MKS-50_battery_replacement.html
Thanks!
Hello, what a great site. I have a question about the LCD. My juno 2 LCD has no light. It also makes a singing noise. Google- fu told me that broken backlight makes the JUNO sing.
How can I fix this? Once I open the juno, I will check 3 dead keys. One works 40% of the time. On black key plays at full velocity most of the time.
I also have the idea that the jack outputs need some attention: I get bad contact ‘noise’ when I touch/ twist the jack cable (outputs) of the juno 2
Greetings from Belgium
Hi Jim,
i am an old Alpha Juno 2 owner, i bring it to life after a 25 years break (and me with) 🙂
I have already cleaned the keyboard contacts and installed a battery holder; my added value is that i relocated the battery holder to a more accessible position under the preset buttons, right under the upper panel so that i do not need to remove the keyboard when i need to replace the battery. I have recorded original factory sounds using a published midi file, via midi load trough a usb-midi converter. All right so far.
I go bad when i try to dump my own sounds to my midifile. I set on sequencer SW Sekaiju the midi input and output (using the same usb-midi interface as used for successfull loading), switch recording on on the sequencer, i activate the dump mode on the synth, “BULK DUMP MIDI” appears on the display and – nothing more happens for dozens of seconds, until i stop the dumping (only LED on usb-midi flashes at around 1 Hz). I do not know if the synth waits for any feedback message from the recieving device or what ??? Seemingly easy, but perpetually failing 🙂
Any advice about backuping Alpha Juno memory presets to a SW sequencer should be helpful.
Thanks and greetings from Slovakia, Europe.
Lubo Janoska
New MKS-50 / Alpha Juno-1 / Alpha Juno-2 Homepage just went live!!!
1300+ Free Tones To Download plus Utilities, Info, Reference – Stop by for a visit sometime.
http://www.llamamusic.com/mks50/mks-50.html
Great article. I got given an alpha 2 from a friend and it is in quite a state so just started to gruelling task of restoring it. Will definitely be using your tips. Thanks again.
Hey me again.
Just wondering if you have any advice for the lack of any sound whatsoever ? Iv’e put my alpha 2 back together and it is not producing any sound. I’ve checked all the cables etc but no luck.
Hi Nick,
I’m sorry to hear you’re having issues with your Alpha 2. Did it produce sound before you stored the restoration? Is it completely dead? Can you play the synth with an external keyboard to rule out any keybed issues? If you could take a couple of photos of inside I might be able to better help. Also, I highly recommend a Digital Multimeter and grabbing a service manual. I put it off so many times in the past, but eventually learned that taking the time to check all the circuits for proper connectivity really helped me to find faulty traces and chips.
Hey Jim
Thanks for the swift reply. Unfortunately i got given the keyboard in a few pieces as a friend took it apart to start the restoration process but never got round to going ahead with it so he gave to me in the hopes that i could finish what he started. Apparently it was working before.
It does fire up even though the LCD back light is very dim everything seems to be working other than the sound.I have not tried to play it through an external keyboard yet , i will give that a go tonight. I have also just managed to download the service manual but to be honest i’m not the greatest when it comes to electronics even though i am very willing!!
I will post some pics as soon as i get a chance.
Thanks again , much appreciated.
Hi Jim,
My Juno 2’s LCD is showing strange characters and lots of hashed instead of words. It’s my first Juno therefore I would not know what I should be seeing but this seems wrong. My request then for advice in two parts.
1) Can I reset the LCD ?
2) In the event of replacing the LCD my research tell me I’ll need to get a new LCD with the HD44780 chip, 16×1 display and a 14pin connector. Does this seem correct ?
Thank you for your time.
Jim,
I have a Roland U20 which the some of the keys are not working.
Do you happen to have a youtube session showing how to repair that?
Thanks,
Mark
Hi there, I have a faulty alpha juno 2 and I thought you may be able to lead me in the right direction in terms of fixing it up… so here’s what it does: when I turn the power on, the lcd becomes faintly backlit but it doesn’t display any letters or numbers, it emits kind of a high pitched mechnical squeal (seems to be coming from somewhere around the lcd), and it doesn’t make any sound at all when any keys are pressed… I tried playing it with a midi controller and I still can’t get it to make sound. Any thoughts on what’s going on with this bad boy?
I have solved almost 90% of all synth issues by simply reflowing solder on the underside of printed circuit boards (PCB). Remove the power supply unit (PSU) PCB and inspect for hairline cracks in solder joints by using a magnifying glass. Reflow solder where needed. Don’t keep the solder tip on any one joint for more than 5 seconds.
CULPRTIS:
1) One possible culprit is the coil on the PSU. Voltage is supplied to the LCD screen backlight from a separate circuit on the PSU. This part identifier is stenciled on the PSU board as L1 and is a 1mH coil (Panasonic P/N: ELE-H102KA, Roland P/N: 12449265). Page 21 of the Alpha Juno-2 Service Notes First Edition shows this coil position at grid L-9 and also at H-1
2) It’s also possible that another component (R1 – R2 – Q1 – C17 – C18 – C19 – T1) within the PSU has failed since these are all part of the same circuit supplying voltage to the LCD backlight.
3) A third possibility is the backlight on the LCD display has gone south or the LCD itself needs replaced
SOLUTIONS:
Since you have stated that you are getting no sound when pressing a key, my best guess would be an issue with the transformer, part identifier T1. Either a bad component or a broken solder joint on the underside of the PSU PCB. To troubleshoot, you could try unplugging the LCD from the board which will eliminate scenario #3.
Additional info here: http://www.vintagesynth.com/forum/viewtopic.php?f=5&t=55534
Removing the main PCB from a Juno-2 is VERY tricky. You can break it without even knowing it. Check here for tips on removing the board:
http://llamamusic.com/mks50/MKS-50_battery_replacement.html#pcbcaution
I bought an Alpha Juno-1, but not under warranty in excellent cosmetic condition.
On getting home I noticed the joystick was stuck to the left. (oh no!) but was an easy fix, (One side of the spring had slipped off the plastic catch) but then on reassembly notes were playing all over the place, automatically pitch shifting and acting crazy, even without touching the joystick.
So I completely cleaned the device as you recommended. I also sprayed the pot with CRC (like WD40) and cleaned the orange contact pad for modulation (activated when pushing the sick forward) with isopropyl alcohol. The allen screw was tight but still the problem persisted. (I never would have noticed that allen screw if not for this article).
I then adjusted the middle metal shaft to vertical (when it was horizontal) and that seemed to fix it for me.
I don’t think I would have known to adjust that middle metal shaft if wasn’t for this article.
So many thanks and as always very informative posts
Hi Jim, some great info on your site.
I have an issue with an immaculate Juno 2 which I recently purchased.
When a sequence of notes is played every sixth note is silent. I play the keyboard in a random fashion and the dead note shifts but always remains the sixth one played.
I put the Juno into test mode and from I can see on the lcd the junk has an issue with voice 3/C as every time the keyboard uses voice 3 no sound is produced.
Do you have a rough idea where I should be looking to find the issue?
Regards
Tom
Hi Jim,
Thank for your great posts on the Roland Alpha Juno 2. One question, I recently bought one and I have to say the previous owner took good care of it because it is in very good condition: no scratch, all rubber keys working, and it got the battery changed recently.There is just the LCD that has no back light, but its perfectly readable black on grey, at least in day time.
One issue however I noticed that the synth produce a slight yet still noticeable hum around the power supply. It is not embedded in the audio signal at all but you feel that the PSU has some kind of strange fixed frequency noise coming out of it. Its not loud but still enough to be heard even with headphones on.
I was wondering if its something that you experienced ? I heard that the coil of the PSU can produce this but I don’t know if there is a way to fix that ? I also own a JX8P. Its bulkier and heavier than the Juno 2 but the power supply is absolutely quite.
Thanks
Pietro
Hi Jim.
Thank for your great resource.
I recently bought a Juno 2. When i turn it on it doenst boot up, but there appears a straight line
on half screen only riser noises in speakers from output… and a half loaded line.. doesnt even reset… i opened it up … there was disconnected connector.. i plugged it… and it started to work… i am amazed by factory presets of it.. BUT i went for dinner came back…. and bang… same again… ive tried everything but the same line stays there any help will be appreciated.
Thanks
TT
My alpha Juno pitch bender was not responding anymore when I push it to the left, actually the synth was always recognizing it as full bend left, all my patches were out of tune once bender range was applied to a patch. I had to remove bender range to every patch to be in tune… I follow your instructions about metal shaft and tiny allen screw and guess what ? It works again flawlessly. Thanks a lot !
An online visitor to my webpage had a real problem with his Bender Bar. Compliments of UPS, four wires were ripped clean off from the precision potentiometer solder lugs after a shipping mishap. Using the schematic to re-wire it is nearly impossible since the pot has no labels. I took my working Bender Bar apart and snapped an image of the correct wiring scheme. I’ve added this as a reference to my webpage at: http://llamamusic.com/mks50/mks-50_info.html#benderbar