Getting low sound with SL-BD20A (Technics)

Hello everyone.
I want to use my old SL-BD20A turntable again. It's been unused for years.
I now have a Yamaha RX-V863 receiver that works fine (CDs, DVDs, radio, etc.).
I plugged my turntable in the phono jacks + the ground of the receiver.
But, the sound is very very low.
I am wondering if it's a stylus/cartridge problem. Or, if I need a preamp. (Maybe both).
Any help?
 
You don't need an RIAA preamp because, as you say, your receiver already has a phono input for an MM cartridge.

I would suspect the cartridge, which is a plug-in, P-Mount T4P type. Perhaps it just needs a new stylus assembly.

If necessary, a complete cartridge replacement is available from the Audio Technica range, and for a very reasonable cost.

It may be worth inspecting the the phono leads connecting turntable to receiver for any damage.

P.S. Try unplugging and reinserting the cartridge into the pickup arm a few times in order to wipe the connections clean.