Juno 106 Sawtooth PROBLEM *FIXED*

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Juno 106 Sawtooth PROBLEM *FIXED*

Postby the.engineer » Tue May 15, 2018 2:52 pm

Hi Everyone,

New here so really hope you can help/advise/etc

I have a Juno 106 s/n 581625 and the sawtooth button does not turn off the sawtooth osc. The led lights up and goes off but the sound is always there, really annoying. I have replaced all the voice chips and wave chips with new analogue renaissance chips.

It does it in normal mode and in test/calibration mode. I have done the calibration steps 1, 2, 3 in the service manual but no cigar there either.

Any thoughts? Is it a buggered IC chip?

Best,
James
Last edited by the.engineer on Wed May 23, 2018 11:58 am, edited 1 time in total.
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Re: Juno 106 Sawtooth PROBLEM

Postby Mooger5 » Wed May 16, 2018 1:03 am

Turn saw off, locate r148 and tr24 in the bottom right corner of the module board, and read the voltage across the resistor. Normally it is +5vdc. If it reads zero volts its probably bad tr24. If it reads +5 then its probablu a broken connection between r148 and the wave ics.
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Re: Juno 106 Sawtooth PROBLEM

Postby the.engineer » Thu May 17, 2018 1:41 pm

Hey Mooger5 thanks for your reply.

I have tested TR24 and all seems fine. I'm getting 5V and the collector pad of TR24 (transistor removed) and I'm NOT getting 5V at the base solder pad of TR24 so there's no 5V coming from pin 12 of IC40.

Thanks again for any and all assistance.

Best,
James
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Re: Juno 106 Sawtooth PROBLEM

Postby Mooger5 » Fri May 18, 2018 12:34 am

What about the voltage across the resistor. It should be +5 with saw off and zero with saw on. If so, then its a broken trace.
Also turn saw on and read the voltage at pin 12. If it reads the opppsite, +5 with saw on and zero with saw off, the ic is fine. If it doesnt read anything, verify the rest of its connections before replacing it.
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Re: Juno 106 Sawtooth PROBLEM

Postby the.engineer » Wed May 23, 2018 11:58 am

Mooger5 thanks for all your help. In the end IC40 needed replacing and I had a synth tech do the work. Thanks again!
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Re: Juno 106 Sawtooth PROBLEM *FIXED*

Postby Mooger5 » Wed May 23, 2018 8:32 pm

Hey, no problem. Glad another Juno is fully working. Cheers!
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