Pioneer PL-400 Jerky Rotation

[gorgonsed]

Hi all,

New to the forum and the hobby. Hoping I can get some help.

Recently picked up a "you fix it" Pioneer PL-400 on Craigslist for cheap. It's having a pretty severe issue where it rotates very quickly for about a half second, then stops hard, goes backwards a bit, then starts quickly in the original direction, repeatedly. It appears to go in perfect 90 degree segments of this action. This happens at both speed settings, 33 and 45. Youtube video of the motion found here :

I've tried contact cleaning the 33/45 fine tuning pots like suggested on here, as well as cleaning the 33/45 speed selector switch, to no improvement. Suggestions welcomed! It'll probably end up as a "for parts" sale at this point though.

 

[gorgonsed]

I'm a moron - works just fine with the platter reattached. It must give too much power, overcorrect, and then continue the process.

If anyone else finds this, just put the platter back on!!

 

[beej]

I was going to post that you really need the platter in place until I read your second post. If you're basing your self-diagnosis on the platter thing then I would suggest that you reassess. Some highly regarded posters on this forum (who will remain forever anon) have made similar mistakes.