JVC VCR HR-S3500U repair?
 

Unit ejects and fails to pull tape back into cassette, mostly after a fast forward, stop, then play. Once playing it shortly thereafter stops and ejects with tape still in machine.
I took apart, cleaned the mode Switch, that didn't help. I looked at the Idler "Hub", the assembly that has the clutch. It's mostly one piece and wasn't sure how to test it. It seems to move ok with clutch in or out position. The belt doesn't seem too tight so maybe it's the belt?
Question is, what is best next step - replace entire Idler assembly "hub" or do I start with a new belt and see if that fixes it?

Thanks for any help! Appreciate your time.

It should not be done with trial and error method. By distance it is nearly impossible to guide repair. But - are you sure you want to repair it? It has no line TBC and not a good JVC example at all, in my opinion.

Welcome. :)

Did you use the service manual?

"Clean the mode switch" has become a stupid meme like "clean the heads". Only people who don't know a damned thing about VCRs are suggesting that. Cleaning a mode switch, and cleaning heads, is not a fix-all for whatever ails a deck. Those should be specific solution to specific problems.

What happens is that disassembling a deck to even get to a mode switch can complicate matters. For the untrained, putting a VCR back together properly is no small feat.

Another truth about VCR repair is that it helps immensely to have a proper working unit to compare against. Not necessarily the same exact model, but one from the same family (not the same brand, but lineage/family).

When a unit fails to pull the tape back, it has an issue with the brakes (or related). I've discussed this in other posts (so has latreche34). I only come across this problem less than once per year, so it's not that common. There can be multiple causes of this.

This is important: Have you ever seen this VCR work properly before? Or was it some sort of thrift/eBay find?

The 3500 is honestly too old to worry about. I'm already reluctant to recommended the 3600/4600 for a non-TBC JVC deck, vastly preferring the 3800/4800 units. 2nd would be the next "model" (29U, 29xx, 59xx). Some of those pre-1996 JVCs were really grouchy, and the x500 decks were the "missing link" between ancient worthless S-VHS and recommended S-VHS. Those x500 exist in "caveat land", use with caution, and you really need to know about your gear.