Best way to fix bad tension on tapes?
 

Recently, I did a full lot check of all of the tapes I have and noticed that many of them have bad tension. I've heard that the best way to fix bad tension is by playing the tape all the way through. This is, however, highly inefficient. Is there a better way of doing this that's more efficient and/or safer?

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This has gone on for a week so I'm going to bump this post

Before randomly FF/REW/PLAY tapes, you need to examine the tapes carefully...

Is there any mold? Even the faintest sign of white?

After FF/REW/PLAY the tape for a very short amount, ejecting, and opening the tape gate, do you see any flaking or missing oxide? Remember that tapes should be smooth glassy shiny black, no imperfections.

What are the brands of tapes?

How old are the tapes? (early/late 80s, 90s, 00s?)

Where, exactly, have the tapes been stored in the past?

What VCR is being used to play the tapes?

Okay so there's no mold problems on any of these tapes. I thoroughly checked and everything is okay.

Secondly, these are from the 1990s and 2000s.

I'm playing these tapes on a JVC SR-VS30U

The tapes have been stored in a filing cabinet since circa 2014.

You need to ask yourself why tension is bad, not just try to "fix" it. The wrong "fix" could ruin both the tapes and decks being used. It may require time to ponder, some experimentation.

Process with caution. :warning: