Roland JX-3P problem with mixing between DCO1 and DCO2

#1

I have a problem with my JX-3P. When I use SOURCE MIX knob in PG-200 during mixing DCO’s levels (between DCO1 and DCO2) every few keys/notes are sounding quieter than the rest and after some time other set of keys/notes are quieter. I made a service diagnostic test and all six voices are fleshing one by one but in random order seems to be ok. I also found that some of the lowest keys sounds not in full like with disappearing second oscillator.

Is it damaged IR3109 VCF chip (it also controls the SOURCE MIX under VCF) or something else?
I have possibility to buy IR3109, but first need to be sure those symptoms are from this chip or something else (small caps in mainboard? I don’t think so).

Will be gratefull for any help, maybe someone had similar problem.

best regards

Rafal

#3

Dear Friends,

After studying service manual, I have noticed that multiplexers/demultiplexers in PG-200 are responsible for MIX between DCO 1 and DCO 2 and also other JX-3P’s functionality. So started from the PG-200. I have replaced three IC’s in my PG-200 programmer. Those chips are multiplexers/demultiplexers: HD14051BP (original old from 80’s). New multiplexers are CD4051BE from Texas Instruments. As for now my problem has disapeared! Everything works amazingly good and even more…All functionality has been improved after changing those IC’s: more stability, more life in sound, more analog than it was before (!!!), and the best of it - it sounds very powerful now it is very close to Jupiter 6, not joking, I’m serious !!! Is it possible after changing just regular multiplexers/demultiplexers in PG-200? Those new IC’s have more voltage tollerance than original IC’s and this is the only difference (maybe here is the secret?) but JX-3P is an analog monster now!

Or…It just sounds like it should after repairing :wink:

Best regards!

Rafal