Sunday, January 22, 2012

Roland JX-8P finally working

JX-8P is working!(for real)

In my previous post I wrote about replacing the rectifiers.
So, I removed the two. One is for the +/- 15V, one is for the +5V.
I'm no expert, but I'd say one of these is in less than perfect condition...


That right one... Hmm.....

Actually, I think the left one was the +5V one and the blackened one was for the +/- 15V, but I got them mixed up after removing them (idiot) so I am not sure.
Judging by the look I would assume the right one was for the +5V though.

Either way, I replaced them with new ones and left the JX-8P on for several hours.
I didn't have a single crash. Yay!
Fixed!!

42 comments:

  1. That's great news!

    My JX-8P won't turn on all of a sudden so I checked out the PS board and the 7V unregulated supply is not happening -- 0V!

    Unfortunately I don't have a 'scope, only a multimeter, which makes things a bit more difficult.

    Could you tell me the part # for those rectifiers? I would love to try swapping them out.

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    1. They're just called W02, that's W zero 2. Found them on ebay.
      Here's where I got mine:
      http://www.ebay.co.uk/itm/W02G-Bridge-Rectifier-1-5A-200V-10-pk-15p-ea-/390345933740

      I guess you don't have any +5V either then, since the +5V gets its power from the unregulated +7V.

      Did you check the fuse? :)

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    2. Yeah, the fuse seems OK, multimeter beeps for continuity. Wouldn't the 15V line go down if it were the fuse?

      Thanks for the part number. I saw it listed as W02 in the service manual parts list but I wasn't sure if there was any more to it. Found the part on digikey too:
      http://www.digikey.ca/product-detail/en/W02G-E4%2F51/W02G-E4%2F51GI-ND/754891

      Have fun with your synth! I can't wait until I can hear it again :)

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    3. Yep, the +/-15 would be dead too, but you didn't say if it was or not, just like you didn't say if the +5V was dead or not, only the +7V, so ... ;)
      Yeah I think I saw them on Digikey too but shipping is a bit expensive for a couple of rectifiers from them if you live in Sweden, unless you have a bigger order to put them in and get free shipping, which I didn't ;) So the UK guy was a better alternative for me that time.
      Good luck with your repairs!

      Delete
  2. Hi, interesting article!
    I'm also having issues with my Jx-8p, and found that a pin on the supply board should give +7v (unregulated) and I get +12,50 instead...do you think this is normal?

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    1. It sounds a bit high but considering the same voltage will feed the 5V regulator it should be 8V I believe to get reliable performance from the 7805 +5V regulator. I also believe the only purpose of the unreg +7V is to power the PG-800 programmer (if you have one), which contains its own +5V regulator circuit powered by that +7V.
      I wouldn't worry too much about it as long as your JX8P +5V regulator isn't on fire :)
      The other voltages are more important. What issues are you having exactly?

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  3. Ooops sorry for my late reply :-)
    My issues are that voice D (the fourth voice of the synth) always hangs when it's played...fortunately it hangs at a much lower volume, so the synth is still playable.
    It's not a contact keyboard issue, because it happens even if I send external midi notes to the synth. And I know it's voice D because I put the synth into test mode, and it's always that voice hanging.

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    1. Hey.
      I don't know exactly what that may be caused by but there's a chance the IR3R05 chip might be bad. If a voice never goes completely silent (like there's always some sound bleeding through) I would suspect the VCA is bad. And in this case, the VCF and VCA are the same chip: Roland IR3R05. However, I wouldn't just start by ripping it out because I'm not 100% sure about it :) It could be something else related to the VCA level control or perhaps it's a trimming issue, but I don't know what to look for and if there's any calibration that should be necessary.
      You could try joining the RolandJXAnalogs or VintageSynthRepairs lists on yahoo.

      http://launch.groups.yahoo.com/group/rolandjxanalogs/join
      http://launch.groups.yahoo.com/group/vintagesynthrepair/join

      Asking around there might provide more help.
      Good luck.

      /Peter

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  4. Thanks Peter, I'm already a member of the Rolandjxanalogs group. Recently something odd happened: was testing the IR3R05 chips, and the multiplexer that feeds VCA signal to them (IC45), the problem was the multiplexer non going to 0 for voice D...BUT while testing, suddenly the problem disappeared! Tried turning off and on again the synth: no more hanging voice... ??? The problem, which was there for almost 3 years, seems to be disappeared.

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    1. Nice!
      In that case I'd guess there's a bad solder joint or something similar somewhere.
      I'm only guessing now, but wouldn't it be more related to IC43 (VCA levels) as I guess IC45 is for mixing the voices together? If you're gonna check for problems, check both IC43 and IC45 with related circuitry.
      Or, if the problem never appears again, forget about it ;)
      Have fun with your JX8P!

      /Peter

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  5. You are right, it was IC43, not IC45. Solders appear good, maybe some creeping current due to humidity...
    Hope the problem doesn't come again. Yesterday I repaired the pitch bend range switch...the last step didn't work,
    There was no more continuity between the relative pin, and the internal contact on the chassis of the switch.
    So i glued a subtle alluminium foil strip over the contact and then wrapped it over the pin to bypass the problem...
    It's somewhat a dirty and cheap repair, but it works!

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  6. Hi Peter, I have the jx-8p and it is taking to long time to boot. After booting, there is no any sound... I have replace the componentes of power supply (caps, regulator and retifier) and keyboard get into normal, but the bottoms from 1 to 9 didnt work... So, I weld again the 8155 (because it has already been welding) and the bottoms start work again, and the booting became is slow again... The 5v retifier gets very hot. Could you give me any tips for me?? Thanks a lot.

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    1. Hi. You mean you re-soldered the pins of the 8155? Was it replaced? That makes me a bit worried. If re-soldering an IC helps, what has happened to that board before? Was it recently repaired? I can't say anything helpful just going by your description but if you say re-soldering an IC helps a bit, I am afraid there may be bad-repair jobs here and there on the synth. The regulators do get very hot, but at least you should be able to touch them for a couple of seconds.

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  7. Hi Peter, I dont know what happened before to this synth, because its from a friend of my. When I opened it, some of the IC wore in socket (8855 and 2 x 74ls138), these sockets I re-soldered and replaced the components but it didnt work. I tested midi out to jv-1010 and it is working, but if I connect midi out to midi in, it didnt work. Is it normal that the initial countdown take so long time? I realized that before the problem initial coutdown was faster. Any other suggestions? Thanks again.

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    1. Hi. You never said how long it takes :) I would say mine takes about 6 seconds.
      With socketed ICs they sometimes need to just be reseated as the IC pins can become oxidized after a while and not quite connect to the sockets.
      It's hard to know what else to do as I don't recognize the problem.
      Perhaps you'll have better luck posting on the yahoo RolandJXAnalogs mailing list?

      Delete
  8. Peter, thanks for your help!! I found out the problem... After replacing the 714ls138 (socketed) the keyboard gets into normal. Thanks again!!

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  9. Great job Peter!

    I recently acquired a Roland JX-8P. Everything works great except I get stuck notes when I hit several keys, primarily the black ones. The notes just sustain and when I attempt to hit them again they don't don't sound obviously because they are sustaining. When I attach a keyboard controller, I can play without any issue at all. The JX-8P is perfect!! Thus no problems when using a controller keyboard. Key bed has been cleaned. Aftertouch works great! I just can't get rid of the sustained notes. I've heard this is a big problem with the JX-8P and there doesn't appear to be a fix. Any ideas?

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  10. I have an intermittent problem where DCO2 will drop out on all voices, but if I tape lightly by the logo, above the main board, this will usually fix it. I have received no help on vintage synth repair. I suspect as this is global, it can not just be one of the six voice cards!

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    1. Hi,
      If you haven't received any helpful reply on vintagesynth I doubt I'll be able to help you as well. I'm on the list and I saw your question but have no idea what can be wrong. After a quick look at the schematics I can only say that if you have any socketed ICs, try to make sure they're properly seated in the sockets. (I don't even know if there are any) Also inspect the board for bad solder joints.
      As you say the problem is common for all voices I would focus on all the logic circuitry from the CPU along the path to the DCO2 control.
      In particular, check IC47 as it's a mux for DCO2.
      Other than that, I really have no idea, sorry.

      Delete
  11. Hi Peter,
    maybe you have an idea. I have a strange error in my ROLAND JX8P. Somehow I cannot select from both the PG800 and synthesizer panel the DCO-2 saw and pulse waveforms or better when this 2 waveforms are selected there is no output sound from DCO-2. When the square and noise are selected the DCO 2 can be heard, however it seems that it is at a little bit lower level than the DCO-1 oscillator. Is this error somehow related to some of the ICs or some other component. It is a little bit strange that this is happening for just 2 waveforms selected. Is there some simple test to know if the some of the voicing modules is broken? Maybe there is some bad solder joint to be done? I need just some clue on which component(s) might be responsible for this, so I can check.
    Thanks.

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  12. Daniel, try disconnecting the PG800, and see if the problem persists. It may be the old DCO2 intermittent problem described two messages up.

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  13. That was a great lead to fixing my Jx8p! It wouldn't turn on, like it had no power. Measured it and 7V unreg. was at 2.9 und 5V was at 1.5. The 7V bridge rectifier looked a little suspicously bodged in, someone had clipped of the original and just solder a new one on. Turns out it had a to low amp rating and literally exploded! Replaced it with an overpowered one and its back up and running. But I noticed one weird thing. According to the circuit diagram and board layout, 7V unreg connects to nothing. Does someone know whats up with that?

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    Replies
    1. Hi, glad it helped you look at the right place :) Unless you see something obvious when looking for problems, always check the power supply.
      The +7V unreg is for the PG-800 connector. It has its own on-board regulator circuit that uses this +7V unreg.

      Delete
  14. Hi Peter! As a fellow Swede, and a recent JX-8p owner, I'm happy that i found your blog! I recently bought the JX in a pretty dodgy state, non-functional and without the power cord, so no testing before buying. As i got it for 500kr (about 45€), i thought that in worst case, it could serve as a parts machine for my JX-10.

    When i got it home and plugged it in, the display just flickered. Reading about your findings, i replaced both W02 rectifiers as well as all the large caps on the PSU.

    On power up the display now shows just a steady "Roland JX-8P 12" message, not doing anything else. Any ideas where i should look next? Tried reseating the Eprom, but no change.

    Any ideas are really appreciated!

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  15. As a follow-up, i have now also replaced the 7805 IC as suggested by others, but the message in the display is still the same.

    The terminals on the PSU all check out ok, except the unreg +7v which reads +12.50v. Is this somtething to worry about?

    I also an unable to get into test mode (Piano 2 + Piano 3 + Power on).

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    Replies
    1. Hi, Sorry to hear about your troubles.
      It's always hard to help unless I have it in front of me.
      Do you have an oscilloscope? I was wondering when you say the voltages are fine if you checked them with a multimeter or with a scope. The unregulated +7V (as I mentioned above) is for the PG-800 only. If the voltages were really bad before, you might have some dead ICs, which is potentially very bad, depending on which ones it is.
      I don't know what it does during the countdown exactly so it's hard to say what causes it to get stuck.
      I'd start trying to figure out what the CPU is doing (or trying to do) and why it's failing to do the countdown. First I'd try to check if it's running at all or if it just hangs. But obviously since you can see the text on the display, there's something happening there.

      Delete
  16. Thanks for your feedback. You don't happen to live in the south of Sweden by any chance? I'm not really that skilled in electronics, when it comes to advanced fault analysis.

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    1. Tell me how to contact you privately by email and we'll continue there :)

      Delete
  17. Couldn't find your email in your signature, so here goes:
    simon punkt matele kanelbulle gmail punkt com

    Hope you can decipher it :)

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  18. Hi Peter...I must say, love the site....as an artist/producer from a hardware generation it's good to see such enthusiasm for proper gear....most of my peers/fans these days are 17 years old and work on a laptop!! Although it has to be said....many of them are now venturing into a hardware puberty! :) Anyway...main reason for getting in touch is I also have as JX8P (with PG800) and it's taking AGES to warm up and get going. On immediately turning it on, you can hear the PSU, but there's nothing on the display...no sound...nothing. But on leaving it for a while...eventually it springs into life and all is well. I then turn it off...turn it back on and it springs into life straight away. I'm no electronics expert but have a reasonable idea of certain things. Could you shed any light on this? Thanks....Richard Earnshaw.

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  20. Hi Peter,
    I've experienced a problem with my JX8P recently, hope you can help.
    Biggest issue being that notes are not played (neither keyboard nor MIDI). In unison mode every 3rd note is not triggered, in poly mode even more keys have no response (like only every fifth note is playable or so).
    However, those dead notes are shifting to the right each time a note is played, so each key won't play once every 3 times any note on the keyboard is played.
    I'm certain the cause of this is a defect chip which shifts the values.
    Also sometimes notes will hold after releasing the key, I was guessing this is a separate issue but hope it could be solved by replacing the same chip.
    If you have an idea which chip it is or if you heard of this before, please contact me.
    Greetings,
    Jan-Lars

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    1. Wow I totally forgot to reply to these comments.
      Jan-Lars, sorry for late reply, but I have no direct idea what could be causing it. Seems you have some problems with some of the voices and the voice allocation makes it rotate which sounds are triggered and whice aren't. It's difficult to get specific but you'd have to analyze if there's one (or more) specific voice that is silent and try to backtrace the problem. That's the most I can say. Sorry I can't be of more help.
      If you live in southern Sweden I can maybe take a look at it.

      Cheers,
      Peter

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  21. Hi Peter!
    It seems you are one of the best sources for JX8p fixing problems... we (all owners of our beloved JX8ps) kindly ask you to provide us a brief guide to the most common problems we will face in the next months / years of use and above all how to fix them. Personally, I have my Jx8p which sometimes is fixed in the start operation at number 12 ...

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    1. Hi,
      I'm not that good :) I just like to fix my own synthesizers and I don't mind putting a lot of time into it. I guess time is something I, unlike people with kids and families etc or other obligations, have a lot of. In any case, and this goes for all old gear, the power supply is always a weak point. I can't say which specific component, as it seems to depend on which part was chosen to have the least margin, but in the JX-8P it would seem one of the rectifier bridges are a bit in the danger zone :P Other than that, the main electrolytic caps in the PSU are always good candidates, but other than that I can't really say.

      Delete
  22. Found this blogspot and It fixed my jx8p that just died 10 years ago.
    I bought a couple of these rectifiers on ebay and replaced the upper one that obviously was boken. Works again!! Thanks a lot!!

    Jonas

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    Replies
    1. Hey, very glad to hear my little post could help someone :) Congratulations!

      Delete
  23. Hello Peter . I have a strange problem with my jx - 8p . namely , all the keys work , have been cleared contacts , switches on the panel as well , and potentiometers . the power is ok, all the voltages are consistent with the documentation , even though something is wrong . When I press a key or a few keys to hear the first loud clip and then impure , distorted sound. Pads are playing almost ok, the piano is distorted, most of the sound is distorted , and every time you hear a loud first clip and then distorted sound.
    This happens in all octaves . where to find the problem? such a signal can be heard from ic59 so the problem is somewhere before . Let's do something about it ?

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  24. Hi everyone and sorry for my English. I own JX8P and for many years everything was OK. I replaced battery about year ago and everything was fine. About 1 month ago my JX8P just stopped make any sounds except some strange noises. When I turn it on it seems like nothing wrong happened. It boot normally but instead of sound there is only the noise. When I play on keyboard and use PG800 I can hear that something is happen but is like there is no sound from DCOs. The noise change when I change presets or play with knobs on PGA .Visually it looks like before. Im not electronic engineer but I just checked and all boards seems to have (+- 5V) Anyone can help me ? Thank You. Adam

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    Replies
    1. Hi Adam, I have exactly the same problem!
      Please, if you find some information, send it to me fabrizio_iorio@hotmail.com

      Delete
    2. Hi,

      I'm sorry, like I commented before it's very hard to guess what the problem can be with your JX-8Ps. Maybe if it happens to be a familiar symptom I can guess a possible problem, but I can't say I recognize this. A lot of things can go wrong after all.
      The general advice is to make sure the voltages from the PSU are stable (check with oscilloscope, not just multimeter) and check all internal connectors for bad contact. Mechanical wear is just as common as component failure in old synths and gets more common the older they get :) Sorry I can't be of more help than that unless you happen to live nearby and let me take a look at it.

      Delete
  25. Hi everyone and sorry for my English. I own JX8P and for many years everything was OK. I replaced battery about year ago and everything was fine. About 1 month ago my JX8P just stopped make any sounds except some strange noises. When I turn it on it seems like nothing wrong happened. It boot normally but instead of sound there is only the noise. When I play on keyboard and use PG800 I can hear that something is happen but is like there is no sound from DCOs. The noise change when I change presets or play with knobs on PG .Visually it looks like before. Im not electronic engineer but I just checked and all boards seems to have (+- 5V) Anyone can help me ? Thank You. Adam

    ReplyDelete