Roland VK-1 Organ leaking tone switches

[couch]

drawbar 2' leak G#4 and 1' leaks A3 when powered on. i have noticed over time of being powered on all the rest of the drawbars will start also leaking the same tones, but more faintly. i have tested D4066c switch no.34 (A3) and 3 of the 4 outs increase alot in resistance when i test with my multimeter. also from what i have so far tested switch no. 30, and 45 have outs that all keep increasing so i assume something is faulty with those switches. also when i play A4 it sometimes stays on. i dont know what to do next, should i order new 4066 switches? should i check the solder joints and see if i can strengthen any weak points there? any help is greatly appreciated

https://soundprogramming.net/manuals/Ro ... eNotes.pdf

[forumuser931182]

Well replacing a 4066 ic would be a quick and cheap test for sure. I don’t know about the life expectancy of a cmos switch, others may have had this experience. With an instrument this age I would expect capacitors to be failing so perhaps it would be good to check power supply voltages in the unit. Maybe the cmos switch supply is low and causing the problem.
Schematic is here: https://www.synthxl.com/roland-vk-1/

Just looked at the circuit… crikey that’s a lot of 4066’s!

[couch]

thanks for the reply, im at a total dead end. i did replace leaky capacitors on the switch board (that has all the 4066) and all other capacitors of the same that were also on the board. i can check the capacitors on the power supply? i feel like either the preamp or the supply might be causing the issue, because most of the 4066 chips are having the same reading with power leaking from the outs

[forumuser931182]

An oscilloscope would definitely be of benefit for your troubleshooting - I have one that is definitely older than the VK-1 haha.
I guess some things you could check by cutting wires or maybe shorting inputs or outputs:
1. Break the G#4 feed from the tone board to the switchboard - still getting noise?
2. Short the output of the G#4 CD4066 ic - can short on the output of the resistor array - still getting noise?
3. Break the G#4 feed from the key switch board. Hard to see which this is on the schematic. May be leaking slight voltage to the CD4066.
Old electronics are a bit trickier to fault find because every component will be suffering from some deterioration however hopefully someone has had a similar problem. No luck on syntaur site eh?

[couch]

id be willing to buy a oscilloscope at this point haha, its really hard to find any information on this organ about repair. yea i posted on syntaur haha, sadly it got 0 replies. with a better understanding whats causing the problem i might try their forum again. but i think taking out one of the problem switches will also help me determine what the problem is specifically.

[resistorman]

If you’re on Facebook, the Vintage Synth Repair and Mods group is quite active. Solid State of Mind has been helpful to me in the past too.

[James Perrett]

4066's (and any other similar CMOS chips) are easily damaged if you don't know what you are doing but they've never struck me as being particularly unreliable when treated properly.

My first thought with crosstalk is to check the grounding everywhere. Just a single connector with a few ohms additional resistance can cause all kinds of issues.