Technics sl 1200 MK2 WEAK SOUND
Regarding the poor sound quality (and possibly the skipping):
check the needle condition, see if exchanging it with a needle (or the entire pickup head) from a working turntable does any good.
Check the pickup connection pins (contacts on the pickup head and on the end of the wires coming through the arm from the unit), see if there is any dirt or oxydation and clean the contacts if necessary, also check for any damage to the wires.
As for the skipping - a heavily worn needle may affect the sound quality and cause skipping as well - if cahnging the needle (or the pickup head) doesn't make a change, try to realign the weight on the tone arm so that the pickup head will become a bit heavier, this could help somewhat (before you actually try to realign the weight, try to put a small coin or a small weight of some kind on the pickup head while it is playing a record, if the skipping goes away, you need to realign the tone arm weight).
This could also be a problem with the tone arm lifting mechanism (may be obstructed by something or damaged so it won't let the tone arm sit properly onto the record and "grab" the groove).
I just mentioned a few things you might want to check, but don't take anything for granted, the problem may as well be elsewhere in the unit.