Juno-106 DCO Bleed?

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cutoffres
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Juno-106 DCO Bleed?

Post by cutoffres » Sat Mar 16, 2024 1:46 pm

I've repaired a few Juno-106 but on this one it's hard to find the fault culprit.

The fault is that even with all waveform off and sub off too i can hear a sort of saw at 60% of the normal volume. It's a bit like a DCO bleed that we should not hear when none wavform is ON.
When the waveform are ON this saw is mixed with the original waveform and then produce a sort of distorted sound.

I had the opportunity to swap boards with an other Juno 106 boards i have and been able to locate that the fault is on the Module board. (the power supply board is the only one i've not swapped) . Previously i've acetoned a few 80017A, replaced some with new 80017A clone, two MC5534A are new, after that everything was working except that DCO bleed!

-Do you have an idea of the problem? Did you encounter that before?
-What is the IC or part of the circuit that indicate that no wave should be played when every wave forms are OFF? As this part of the circuit could be the fault source?
I really need help for this one, thanks.
the Juno-106 service manual: https://www.synthxl.com/wp-content/uplo ... Manual.pdf

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Mesmerised
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Re: Juno-106 DCO Bleed?

Post by Mesmerised » Sun Mar 17, 2024 1:44 pm

I would carefully check the board and the lines around the voice chips! Since desoldering these is not an easy task it can happen that some connections get damaged. Some lines go even through/under the connectors. I had to rebuilt 4 wires when searching for the faults in my Juno after swapping the voice chips. Carefully test every connection around the chips. (Ground also)

cutoffres
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Re: Juno-106 DCO Bleed?

Post by cutoffres » Sun Mar 17, 2024 4:15 pm

I've triple checked and unfortunately that not a connection problem after desoldering/soldering. Thank you.
I need to find the chip that tell the voices to play or to be silent.

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