hifi engine

Sansui turntable SR-717 catches sound like a microphone

Hello folks,
I am a newbie to turntables. I acquired a Sansui turntable in a decent shape,but it was missing the three small weights . I looked in the operation manual when I found out these weights were missing . I googled the thing and I found out that one acts as anti skating and it should weigh 2 grams and the lateral is about three and half grams. However there is an extra weight on the rear of the tone arm which I couldn;t find any info about.. I managed to make the first two at a metal turnary. Now the TT is working ,but I feel there is something missing in the sound.

The persisting problem is that it catches sound from the surrounding . Any contact with the body will make the TT sound like a microphone.boooooooooom.. booooooommm.
I checked wires, including earthing wire. everything looks normal.
any help is greatly appreciated
thanks in advance.