Juno 106 - problems with oscillators

[tertiumsquid]

Hi all, I've got a Juno 106 on my bench that I'm trying to get back to 100%. I've done the acetone "fix" on the filter chips (which worked brilliantly), but there are still a couple problems standing in my way.

Voice 5 has no sub oscillator. I swapped the 5534A chip from voice 5/6 to voice 3/4, and the problem followed the chip, so I'm assuming that's a dead part on the 5534A.

Voice 3 has some weirdness with the saw wave. If I go into test mode Poly 1+2 (cyclic voice mode) and repeatedly press the same key, I get something that looks like a PWM'ed sawtooth on voice 3 (see pics). If I press a different key before voice 3, I get some sort of amplitude/ring modulated pitch of the previous note. I believe that followed over when I swapped the 5534A chips, but I'll confirm by swapping them again tomorrow morning. I'm also assuming another dead 5534A, but if anyone has other ideas, let me know.

The last problem I'm working on is calibration. I've got everything in the Roland manual calibrated perfectly up until step 10 - pulse width. No matter how much I adjust VR31, I can't get pulse width to 50%. Max I can get is about 30%. This is tested with an oscilloscope on the test points TP8-13, as well as from audio output. The trimmer for PWM is a 20k in line with a 56k resistor - I'm thinking if I change the value of that resistor (R118) to something higher, I'll be able to get to 50%. Does anyone know of any issues with that plan?

I've got some screenshots of the waveforms I'm getting from the audio output:

[almazmusic]

What kind of osciloscope did you use to calibrate Juno-106 via service manual?

[synzoneau]

Hi

Looks like you've got the same problem as me. Did you solve this ? It's driving me up the wall. On mine voices 4 and 5 behave this way and I swapped the waveshapers for new AR's the problem is still there. Voice chips are AR's. The only progress I've managed to do that one went silent like you posted I put in a new 4052 that seemed to solve that problem. I also swapped the DCO timer chips IC33,IC34 to no avail and the chip select IC36 also to no avail, if you scope IC33 and 34 those you will see the squarewave clock is distorted for the bad voices.
I can confirm that what's happening is that the for the bad voices instead of say 4 playing you're getting a mixture of that and the previous voice. The PWM thing I didn't notice it could be a clue, I'll try it on mine. I know this is an old post but please please reply if you've solved this !

[MxLZR]

Also check the transistor(s). I repaired one and the sub-oscillator wasn’t working. Tr19 was faulty. Replaced and is now fine