National 830 repair

[rustykrabpizza]

I never heard about VHDs until last week, so I am a fresh baby here. I just received two junk National DP-830s, and trying to do my research to learn how to repair them a bit. I then ran into this forum post through google searches. This isn't my strong suit, considering I only work with game consoles.

One is complete junk, motors are bad, belts are starting to go bad, and couldn't get it to accept a cardtridge, and then 3 of the plastic latching pieces snapped off when I was fiddling with the gears to try and get it to accept the disc (The outside metal of this one looks like it has old mold or something on it so the plastic is probably rotting inside).

The other one, however, takes a disc and plays the one movie that I have, but there is jittering right to left across the entire screen, and the jittering is stronger on the upper half. I'm not sure if this has to do with sending the signal to my 4k tv (its the only thing I have to test it on), the needle, or something to do with the board of the player itself. I wonder if the needle is in good shape to sell, but I have no idea how to diagnose what is creating the screen shake. If I find out the needle is good, and find out the player isn't repairable, it is possible that my friend could put the needle on his store, but that would ultimately be up to him.