QUAD receiver Jvc 4-vr5446

Hello,

I've just purchased Jvc 4-vr5446 in good condition. I hadn't the opportunity to test its sound, functions etc. Primary idea was to use it as a demodulator as it is equipped with almost all major decoders - SQ, QS, CD-4. It works and all functionality is OK apart for one but quite important. When you switch to PHONO input in the speakers starts a noise like uproar bluster kind of inner interference.. It is not present in RADIO mode so further chain like external amplifier or speakers are out of suspicion. It is increasing with loudness and is present even without turntable switched in. It is present in all switches positions like MONO, STEREO, CD-4, Matrix. All decoding, separation etc works well though but the sound is affected badly

Do you have any ideas the result of what what this could be? The receiver itself is 40 years old - maybe some details worn out like condensers?

Anyone faced such situation? Please share your experience

Or should I start looking for someone who repaires vintage hifi

Thank you

Sergey