The real problem was bad trace on KLM-366, -15V trace near connector from PSU. It's now with original optocoupler and original resistor. No problems anymore. Tried with VTL5C9 and original resistor, but only three lower octaves are ok. I've been told that VTL5C9 will be fine with original resistor, but it seems that it's not true. At least in this case. Or my VTL5C9 was bad.
Thanks everyone!