Search found 56 matches

by polysixer
Sat Nov 17, 2018 1:22 am
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

Oh yeah I know, nothing special about those, just pointing out for future reference as source, I couldn’t find them locally.
by polysixer
Fri Nov 16, 2018 11:39 am
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

For reference, this is where I got my original NOS 2SC2878A pair:

https://www.soundtoparts.com/en/compone ... c2878.html
by polysixer
Wed Nov 14, 2018 9:50 pm
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

Nope. Mine sounds the same, normal as usual... Yes, you get a very distinctive distortion in some settings when these degrade. You can hear it in most of Synthmania’s Juno-60 videos and others. I wonder how many confuse this issue with faults on the MN3009 BDDs. I’ve seen this as a suggestion in mo...
by polysixer
Tue Nov 13, 2018 1:58 am
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

Ok I fixed this. I can confirm it was the muting transistors that were degraded, TR7 and TR8. You have to replace them with the exact part numbers 2SC2878A, no equivalents or others will do (I had put equivalents with the same specs when I began investigating the issue. Both the originals and replac...
by polysixer
Mon Nov 12, 2018 12:35 pm
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

Any news?? It´d be good to know if at least one worked :thumbright: Sorry, been out of the loop for a week. Logarithmic slider did mostly fix the issue, though still present on extremes and I'm not really that fond of the resulting curve. Increasing resistance at R36 seems the most obvious better s...
by polysixer
Fri Nov 02, 2018 7:47 pm
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

It´s intriguing because the positive supply is what tames down the control voltage, like take -10V, add +5V and the sum is -5V... Have you traced the entire control path? Another curious thing is the 10k law faking resistor for vr3 seems an afterthought, as it has no ref. number and there´s no sign...
by polysixer
Fri Nov 02, 2018 6:24 pm
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

ha! where is r165?? Are you going to decrease the resistance of r165 from 15k to say 10k? Well it seems the first revision of this board is made to cope with the linear signal and designed not to have R165 present at all (I’ve seen pictures of the other side too). It’s the same in every other way a...
by polysixer
Fri Nov 02, 2018 5:27 pm
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

Take a look at this very early board revision and tell me if you see something weird about the VCA scaling resistors ;) http://www.spheremusic.com/userimages/Img15647-4.jpg I think I might be fixing this today, though your method of turning the signal into logarithmic should also work (cause that's ...
by polysixer
Fri Nov 02, 2018 1:31 am
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

Mooger5 wrote:Ok. So, its actually only one slider. Sorry. Its vr3 lfo. Note the 10k resistor. Do the same for the vca level slider and that should fix it. Bye now.
I will definitely try this and let you know. Thanks a lot for all the efforts, really appreciated.
by polysixer
Fri Nov 02, 2018 1:20 am
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

No. I was wrong. It´s only a common voltage divider, no law change at all. Your chorus board seems fine. Which is the more puzzling. This is what I'm realizing too, for every suspect thing I look into everything seems normal in the end. I've also checked those groundings leading to IC5 with no issu...
by polysixer
Fri Nov 02, 2018 1:08 am
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

Mooger5 wrote:
Mooger5 wrote:
Voltage across pin7 of connector for VCA Level and ground:
-5 = +3.84V
0 = +2.74V
+5 = -6.13V
polysixer wrote:
Connector Pin 7

-5: 3,89mV
0: -0,78mV
+5: -6,18
Wait. Just to be clear, your readings there are in actual Volts, not miliVolts, right??

Sorry, Volts. Typo there.
by polysixer
Fri Nov 02, 2018 12:04 am
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

EDIT: Just to make it clear, that "pin 7 connector" (vca level line) is at the end of a wire loom leading to a header on the main board. Pin 5 on that header corresponds to pin 7 in the chorus board connector. By disconnecting the entire chorus board, it´s possible to read the unadultered voltage a...
by polysixer
Thu Nov 01, 2018 1:35 am
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

Meh scratch that. There is actually a difference between my old 50K and the new ones in that the old one measure 90K and the new are 50K but maybe because they're stereo faders or something like that, not linearity. Swapped the level slider just in case and the behavior is the same. Anyway, measurem...
by polysixer
Wed Oct 31, 2018 8:11 pm
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

TR5 - emitter is indeed to -15 but collector goes into +15 through R46 and R50, so just wondering if a failure in this transistor explains the resistance drop of R165 in circuit. That could explain the scaling fault I guess. Furthermore, why does R17 connected to the same +15 line measure correctly...
by polysixer
Wed Oct 31, 2018 4:30 pm
Forum: HELP!
Topic: Juno 106 - wierd distortion fault
Replies: 69
Views: 15411

Re: Juno 106 - wierd distortion fault

TR5 - emitter is indeed to -15 but collector goes into +15 through R46 and R50, so just wondering if a failure in this transistor explains the resistance drop of R165 in circuit. That could explain the scaling fault I guess. Furthermore, why does R17 connected to the same +15 line measure correctly ...