Thank you for the suggestions, retiredcaps.
1. Cleaned 1 year ago (part was corroded), then it was dead brick. I have repaired missing traces and still dead. After 1 year I have returned to it and it runs, but some values are off, some floating (decreasing ohms)
2. PTC 1,11k
3. Rotary switch looks OK to me, clean
4. Jacks looks OK
It is OK to flood some true hole connections with solder? I have an bad feeling that that ones, which have been corroded may have loose connections inside in middle layers of PCB.
Measured values:
VDC open 0.035V, closed 0.03V
mVDC open -60mV, closed -1.9mV
ohms open 12-20M
ohms closed 12 and decreasing to 1 for 1-2 minutes
9v bat with Fluke 179: 9.34V
9v bat with other dmm: 9.5V
Thanks again for help