Pioneer Pl990 turntable sounds awful.... I have a pioneer pl 990 record player connected to a pioneer amplifier and a sony CD player. when I play an LP, the sound is bass heavy and I can hardly hear t

Pioneer PL 990 Manual Belt Drive Turntable Vinyl Engine cheers john. Stylus City

You need to hook it up to another analog input other than the phono input. The record player has a built in preamp, and the receiver's phono input has a separate preamp for non-amplified players. You cannot have the two hooked to each other.

If the player has a MD/MC pickup head, you need to use an input suitable for MD/MC
(Magneto Dynamic/Moving Coil). If that is not available, you need to buy a standalone
phono pre-amp (pre-amplifier with RIAA-correction curve). Like the TCC TC-400G/L.
Example: See HERE and some info HERE.

No you cannot play while lid is closed and YES you need an amp/receiver amp

I suppose the only way to do it would be to stop it functioning completely. The only way would be to dissasemble the auto function. What you would need to do is work out which parts are essential for the turntable operation and which only activate the return. So you need to whatch the mechanism working. You will need to remove the base and look at from underneath, just like going underneath a car!
I can't say for certain if you can do it, only you will be able to determine it can be removed without affecting the operation of the entire turntable.

try cleaning the inner ring on the underside of the actual turntable platter and also the motor spindle using isoprynol alcohol or use neat clear spirits like bacardi/vodka with cotton wool etc. if black residue comes off either the platter or the motor spindle that will be residue from the old belt that could cause the fluctuation in speed? good luck.

Yes first check is that the Gnd wire from your turntable is connected to the Gnd (ground) post at the back of your amplifier with a good clean tight connection.
If the problem persists, check ALL your hi-fi components mains plugs for earth connections including your turntable, then remove the earth connections on all but one component so that you are left with only item earthed.
What does sometimes cause problems is if 2 or more hi-fi separates are earthed and connected to each other the earth cables along with the hi-fi interconnects form an inductive loop that picks up interferance such as mains hum etc.
Regards John

The turntable does not turn. There is a black rubber band type that needs to be looped around the gears. How do I do this?

Confirm that the stylus you bought is spec'd out for that turntable
Also check all four wires to the cartridge