Hello, I have a super star 3900, which had been abandoned for years, it has a curious problem, and it is that in usb, it is not stable in frequency, I checked the quartz crystal of 14,010, I have also checked the adjustment coil of usb l21, I have immersed the mode selector in isopropyl alcohol and washed by ultrasound, without success. it is a symptom similar to when the ceramic filters fail in a vhf equipment, greetings
