MUFF WIGGLER Forum Index
 FAQ & Terms of UseFAQ & Terms Of Use   Wiggler RadioMW Radio   Muff Wiggler TwitterTwitter   Support the site @ PatreonPatreon 
 SearchSearch   RegisterSign up   Log inLog in 
WIGGLING 'LITE' IN GUEST MODE

Jupiter 8 Troubleshooting!!
MUFF WIGGLER Forum Index -> General Gear  
Author Jupiter 8 Troubleshooting!!
mattjhuber
I have spent many hours scouring the forum(s) for some answers, and have found some to many of my questions, but I figured I would employ the help of the wonderful community here for some of the issues.

SO, I have a Jupiter 8, 12bit. I am about to order the caps for the PSU, and get that guy in spec, but I have a few other issues I need help resolving:

1. Voice 4 is having filter issues. Sometimes it sounds like it is just duller than the other voices, other times, it sounds like it isn't following the same envelope at the other voices.

2. Voices 5-8 have a strange issue. When VCO Mod is engaged and the fader is pushed up, these voices will bend up almost a whole semitone without the LFO trigger being depressed. The same happens with VCF Mod -- it will open up the filter slightly when the fader is pushed up.

3. Some voice bleed / background noise. I understand that there was a service note about this -- cutting the ground trace & soldering in a 100ohm resistor. I have looked at the diagrams, and my boards look a little different, so I wanted to see if I'm thinking about it correctly. I have diagrammed what I believe I should be doing...is this right?



Thanks SO much for any thoughts you folks may have!
mattjhuber
Bump! Currently going through & cleaning the beast -- about to start digging in and addressing the above issues. I'd love any help / counsel!

Thanks so much!
m.o
Personally I would hesitate to start cutting pcb traces on a $8000 (or however much they go for now) synth, unless I was very sure about what I was doing.. eek!

Sorry I can't help with the specifics.
mattjhuber
m.o wrote:
Personally I would hesitate to start cutting pcb traces on a $8000 (or however much they go for now) synth, unless I was very sure about what I was doing.. eek!

Sorry I can't help with the specifics.


It's a factory modification they started doing after the first several hundred units to address a voice-bleed issue. Is there another way to solve it?

Also, does anyone have any thoughts on the envelope issue on voice 4? Is this something that full calibration would likely fix, or does this seem to be a different issue?

I just finished re-capping the PSU, and that went swimmingly. Things are very stable in the power section now!
oldgearguy
I did the VCA bleed mods on a couple very old 12 bit JP8s and it was noticeably better. I pulled the ECO from the synthfool site on what needed to be done.

The other audio thing to check is to drop the far left front panel board with the volume control and look to see if the output stages have some non-polar caps in the path. They'll be big and obvious if they are there. Replace with same type/ value.

I'll need to re-read the info you provided when I have more time to discuss the other issues.
oldgearguy
First thing I do when I suspect a voice issue is to move the voice card to the upper layer and if it's already there, swap places with it's neighbor to verify the problem is actually on the card and not in the controller card or cable.

If you have a dual probe scope and/or dual voltmeters, verify the same signals are going into the filter and coming out and verify the same amount of control voltage is going in as well. You can do one at a time, but it just means you have to take more notes.

The issue with the left hand controller section seems to be more common as the JP-8 ages. I've tried doing a very tight calibration and it minimizes things, but it still happens. I was never able to fully solve it and was one of the contributing factors in my decision to move on (same w. the XMod behavior). I'm not convinced the issue is in the left hand board. I'm not sure if I did a cap replacement on that board, so that may be something. There could be some leaking transistors, but given Roland used the same parts across the unit and the rest of the machine doesn't seem to be impacted by transistors going bad, it's a less likely cause.

I would start with a schematics tracing to see how the control voltage from that side is mixed into the main voltages from the controller card(s). Since the problem only happens on voices 5-8, try swapping controller card positions and see if the problem follows the controller. If it does, then focus on where those cv's are coming in and stored/combined with the rest.
mattjhuber
Thank you so much oldgearguy! I was secretly hoping you'd drop by -- your posts have been so incredibly helpful for you. When I get the chance to do some voice card swapping, I'll report back.

Thank you SO much for the help!
mattjhuber
Hello my friend! Thanks so much for the help so far -- would you be able to tell me (looking at my picture above) if I have the right idea with the voice bleed modification?

Thanks so much!

oldgearguy wrote:
First thing I do when I suspect a voice issue is to move the voice card to the upper layer and if it's already there, swap places with it's neighbor to verify the problem is actually on the card and not in the controller card or cable.

If you have a dual probe scope and/or dual voltmeters, verify the same signals are going into the filter and coming out and verify the same amount of control voltage is going in as well. You can do one at a time, but it just means you have to take more notes.

The issue with the left hand controller section seems to be more common as the JP-8 ages. I've tried doing a very tight calibration and it minimizes things, but it still happens. I was never able to fully solve it and was one of the contributing factors in my decision to move on (same w. the XMod behavior). I'm not convinced the issue is in the left hand board. I'm not sure if I did a cap replacement on that board, so that may be something. There could be some leaking transistors, but given Roland used the same parts across the unit and the rest of the machine doesn't seem to be impacted by transistors going bad, it's a less likely cause.

I would start with a schematics tracing to see how the control voltage from that side is mixed into the main voltages from the controller card(s). Since the problem only happens on voices 5-8, try swapping controller card positions and see if the problem follows the controller. If it does, then focus on where those cv's are coming in and stored/combined with the rest.
mattjhuber
Okay! I got the voice 5-8 issue solved...it was just a calibration issue.

AND, a big aha! moment with the envelope issue on Voice 4...it ONLY follows Envelope 1...if I switch over to Env 2, Voice 4 behaves normally.

I'm assuming this helps narrow my search, but I'm admittedly still getting my bearings on the circuit. Any help would be great!

Thanks!


oldgearguy wrote:
First thing I do when I suspect a voice issue is to move the voice card to the upper layer and if it's already there, swap places with it's neighbor to verify the problem is actually on the card and not in the controller card or cable.

If you have a dual probe scope and/or dual voltmeters, verify the same signals are going into the filter and coming out and verify the same amount of control voltage is going in as well. You can do one at a time, but it just means you have to take more notes.

The issue with the left hand controller section seems to be more common as the JP-8 ages. I've tried doing a very tight calibration and it minimizes things, but it still happens. I was never able to fully solve it and was one of the contributing factors in my decision to move on (same w. the XMod behavior). I'm not convinced the issue is in the left hand board. I'm not sure if I did a cap replacement on that board, so that may be something. There could be some leaking transistors, but given Roland used the same parts across the unit and the rest of the machine doesn't seem to be impacted by transistors going bad, it's a less likely cause.

I would start with a schematics tracing to see how the control voltage from that side is mixed into the main voltages from the controller card(s). Since the problem only happens on voices 5-8, try swapping controller card positions and see if the problem follows the controller. If it does, then focus on where those cv's are coming in and stored/combined with the rest.
oldgearguy
mattjhuber wrote:
Okay! I got the voice 5-8 issue solved...it was just a calibration issue.

AND, a big aha! moment with the envelope issue on Voice 4...it ONLY follows Envelope 1...if I switch over to Env 2, Voice 4 behaves normally.

I'm assuming this helps narrow my search, but I'm admittedly still getting my bearings on the circuit. Any help would be great!

Thanks!


oldgearguy wrote:
First thing I do when I suspect a voice issue is to move the voice card to the upper layer and if it's already there, swap places with it's neighbor to verify the problem is actually on the card and not in the controller card or cable.

If you have a dual probe scope and/or dual voltmeters, verify the same signals are going into the filter and coming out and verify the same amount of control voltage is going in as well. You can do one at a time, but it just means you have to take more notes.

The issue with the left hand controller section seems to be more common as the JP-8 ages. I've tried doing a very tight calibration and it minimizes things, but it still happens. I was never able to fully solve it and was one of the contributing factors in my decision to move on (same w. the XMod behavior). I'm not convinced the issue is in the left hand board. I'm not sure if I did a cap replacement on that board, so that may be something. There could be some leaking transistors, but given Roland used the same parts across the unit and the rest of the machine doesn't seem to be impacted by transistors going bad, it's a less likely cause.

I would start with a schematics tracing to see how the control voltage from that side is mixed into the main voltages from the controller card(s). Since the problem only happens on voices 5-8, try swapping controller card positions and see if the problem follows the controller. If it does, then focus on where those cv's are coming in and stored/combined with the rest.


If envelope 2 is working on the filter and envelope 1 is working on all the other voices, that definitely narrows down the search. Take a look at the schematic on the right side of the Module board. You'll see a pin for Env 1/2 (37) and you'll see the VCF Env Mod (45). There's also pins for each of the ADSR stages. There's also the VCF Cutoff line (47). By tracing around these areas and comparing the various bits with the envelopes set to the same shape and flipping the Env 1/2 switch you may be able to narrow down the issue.
MUFF WIGGLER Forum Index -> General Gear  
Page 1 of 1
Powered by phpBB © phpBB Group