Changers,....
Scads of moving parts, and old grease. The grease cakes and parts start to falter.
If you can get under the hood, check the tonearm wires to make sure they haven't been tangled up in something
Are you familiar with the balancing steps?
~ zero-out, or remove any anti-skating mechanisms
~ float the arm at neutral horizontal attitude by adjusting the counterweight until the arm floats at horizontal.
~ Add vertical tracking force load (VTF) to the needle.
Typically this is around 2grams, +- a couple of 10ths of a grams (from 1.5gr low side to 2.5gr high side, typical averages - 2.0gr lands you right in the middle in safe ground.). An older US penny weighs just over 2gr; so if no scale available, float the arm, and apply a penny to the headshell; works.
~ Reset your anti-skating mechanism values.
You might find a reference for it at the vinylengine website. They have a bunch of manuals and service manuals there. You'll need to join in order to d/l any files.
Its a website just like here.