My Juno 60 is dead. Any help?

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ChuckFalcon
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My Juno 60 is dead. Any help?

Post by ChuckFalcon » Fri Sep 30, 2016 8:22 pm

Hi everyone! The Roland Juno 60 is my favorite poly. I have had 2 (working) in the past but I have since traded or sold them. I found one recently on the cheap because it doesn't work. Here is what it DOES do when I turn on the power:

-The LED about the "hold" button lights up
-None of the other LEDs light up, not even the numeric lights
-No sound at all when coming out of the output.
-I checked the power that is coming from the power board at the power board and all the numbers are reading correctly.
-The "hold" button doesn't seem to latch or unlatch

At this point I am unsure of what to do or check. I can use a DMM, soldering iron, and I own an oscilloscope. Does anyone have any advice on how to go about checking or testing? Has anyone else out there experienced this or know how to fix it? Any help at all and I would be most appreciative.

Thanks,
Chuck

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Re: My Juno 60 is dead. Any help?

Post by ChuckFalcon » Wed Oct 05, 2016 10:33 pm

BUMP

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Werecow
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Re: My Juno 60 is dead. Any help?

Post by Werecow » Sun Oct 09, 2016 1:48 am

When a synth is that dead, the possible problems comprise an almost infinite number of permutations. And with a unit that complex, troubleshooting (especially remotely) can be extremely frustrating, to say the least.

If you don't have the complete service manual, download it. It has voltage measurements, logic tables, waveforms, cal procedures and descriptions of circuit operation that can be quite helpful.

If I had the synth in front of me, I'd check the basics first. Even though the P/S DC output levels may look good, also check ripple (AC) voltages at those points. The synth is going on 35 years old, so electrolytic caps should always be suspect if they haven't already been replaced. Check to see that the white connectors are seated properly on all the boards. Measure and verify that the P/S output connections, including grounds, are actually getting where they're supposed to be on all the other boards.

Check to see that both μCs are being allowed to start. Pin 4 should be momentarily at low logic level on power-up, then go high. Pins 2 & 3 should have a 5V P-P sine wave (not pure sine though, as these always have a bit of distortion) at the crystal frequency. With the scope, check for good 0-5V logic levels on the μC ports (pins 12-19, 21-24 and 27-38). Any "partial" logic levels indicate a problem either going into or coming out of the μCs.

Beyond that -- you're troubleshooting a synth with essentially two 8-bit computers in it, so you can understand that it would be difficult, if not impossible, for someone to walk you through it. :(

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Re: My Juno 60 is dead. Any help?

Post by garranimal » Sun Oct 09, 2016 5:40 pm

Check the internal battery?

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Re: My Juno 60 is dead. Any help?

Post by ChuckFalcon » Tue Oct 11, 2016 11:51 am

Thanks for all of the info!

Noob question: what are the "uC"'s that you are talking about? If that is the main CPU chip then. I am thinking that it may possibly be an issue with one of those chips because it as though its not even booting up, but then again it could be about anything.
Werecow wrote: Check to see that both μCs are being allowed to start. Pin 4 should be momentarily at low logic level on power-up, then go high. Pins 2 & 3 should have a 5V P-P sine wave (not pure sine though, as these always have a bit of distortion) at the crystal frequency. With the scope, check for good 0-5V logic levels on the μC ports (pins 12-19, 21-24 and 27-38). Any "partial" logic levels indicate a problem either going into or coming out of the μCs.(
Another noob question: on Juno boards there are areas labeled as "test points" at these areas, what am I testing for? Continuity, voltage, wave form purity? All the above?

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Re: My Juno 60 is dead. Any help?

Post by ChuckFalcon » Tue Oct 11, 2016 11:55 am

garranimal wrote:Check the internal battery?
I thought that the battery was only there to save memory. It is possibly bad but I can't even get to the part to attempt to make a preset to save yet.

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Re: My Juno 60 is dead. Any help?

Post by garranimal » Wed Oct 12, 2016 4:43 am

ChuckFalcon wrote:
garranimal wrote:Check the internal battery?
I thought that the battery was only there to save memory. It is possibly bad but I can't even get to the part to attempt to make a preset to save yet.
Most synths from the era have a CPU/memory protection circuit when the battery starts dying. Test the battery with a DVM to eliminate it as suspect.

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Re: My Juno 60 is dead. Any help?

Post by ChuckFalcon » Wed Oct 12, 2016 3:36 pm

[/quote]
Most synths from the era have a CPU/memory protection circuit when the battery starts dying. Test the battery with a DVM to eliminate it as suspect.[/quote]

The battery is reading 3.2V so I guess its good. I was really hoping it was the problem. At least we can eliminate that as an issue.

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Re: My Juno 60 is dead. Any help?

Post by madtheory » Wed Oct 12, 2016 4:00 pm

ChuckFalcon wrote:Noob question: what are the "uC"'s that you are talking about?

Another noob question: on Juno boards there are areas labeled as "test points" at these areas, what am I testing for? Continuity, voltage, wave form purity? All the above?
Answer both questions by reading the service manual. It's a very good one.

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Re: My Juno 60 is dead. Any help?

Post by Werecow » Thu Oct 13, 2016 1:39 am

ChuckFalcon wrote: Noob question: what are the "uC"'s that you are talking about? If that is the main CPU chip then. I am thinking that it may possibly be an issue with one of those chips because it as though its not even booting up, but then again it could be about anything.
μC = microcontroller. Both IC14 and IC56 serve equally important functions, and neither depends on the other to operate, so I wouldn't call either a main CPU, in this case, even though one is on the "CPU board" and the other isn't. But your thinking is the direction I was going -- if either wasn't booting for any reason, you'd end up with a quite dead keyboard. After checking the mechanical stuff and voltages at the individual boards, they would be next on my list.
Another noob question: on Juno boards there are areas labeled as "test points" at these areas, what am I testing for? Continuity, voltage, wave form purity? All the above?
On these boards, the test points are laid out as voltage and waveform reference points for the calibration procedure, but are also good troubleshooting aids.

As madtheory said, the service manual is quite good. What it doesn't tell you is how to troubleshoot, but that's a matter of experience, and knowing where to ask if/when you get stuck (and you will). So get it. A quick Google should yield several locations. Doooooo ittttt now! :)

B.

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Re: My Juno 60 is dead. Any help?

Post by ChuckFalcon » Fri Nov 04, 2016 4:50 am

................

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Re: My Juno 60 is dead. Any help?

Post by ChuckFalcon » Fri Nov 04, 2016 4:52 am

Werecow wrote:
μC = microcontroller. Both IC14 and IC56 serve equally important functions, and neither depends on the other to operate, so I wouldn't call either a main CPU, in this case, even though one is on the "CPU board" and the other isn't. But your thinking is the direction I was going -- if either wasn't booting for any reason, you'd end up with a quite dead keyboard. After checking the mechanical stuff and voltages at the individual boards, they would be next on my list.

On these boards, the test points are laid out as voltage and waveform reference points for the calibration procedure, but are also good troubleshooting aids.

As madtheory said, the service manual is quite good. What it doesn't tell you is how to troubleshoot, but that's a matter of experience, and knowing where to ask if/when you get stuck (and you will). So get it. A quick Google should yield several locations. Doooooo ittttt now! :)

B.
OK, I am back at the Juno 60. After fixing a 106's noise generator and missing square wave.

I have some new clues and info:

-There IS sounding coming from the synth but it can only be heard with the output set to "H" and the volume turned up. Its a single note ringing out infinitely.
-When you turn on the synth sometimes the note is there, sometimes it isn't. Sometimes the note is a square wave, sometimes its a triangle, some times its sub. Sometimes it 2 of them sometimes its all of them. Its totally random without me moving the boards at all. Sometimes the perceived volume is louder too.
-The Keyboard seems to have no effect at all. However, the ringing not DOES change with the "bender", "LFO trigger".

-I tested voltages at the power supply they are correct and then I tested them entering each board and they are all testing good at entry.
-IC56 on the CPU board gets VERY HOT to the touch when left on for about a minute. Perhaps its faulty? Is there a way to tell? The other Iu chip (IC14) does not get hot to the touch.

In the service manual all I really see is stuff on how to adjust and correct a juno 60 that is already KINDA working adjusting wave forms, envelopes, etc. Where can I go from here as far as testing and bringing it back to life?

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