Model M's - some resonate, some don't?

[didjamatic]

I have a few Model M's and have noticed they all feel different.

The one I'm using now is a Silver Label 1390131 (Aug 88) and feels very solid with very little "resonation" when typing.  

A 90's Lexmark blue label that has never been used (1 piece keys, fixed cord model) has a little bit of resonating.

A 87 Silver label 1390131 resonates a lot.

A 1987 Model M terminal board that I had but sent back (not pc compatible) was extremely solid, it felt new and had almost no resonation of any kind.

Is this resonation from overuse, luck of the draw or something else?
Is there something you can do to quiet it down and make the board feel more solid?  I love the clicks but don't like the resonating/reverby/pingy sound that echoes through the case on some of them.

[ch_123]

Probably plastic rivets and maybe spring wear... Have you ever opened them up?

[didjamatic]

The terminal board looked identical to my other Model M's, but had a connector on it that wasn't XT or AT.  So nice I hated sending back but it wasn't compatible with PC.

As for that bolt mod, holy smokes that's extreme!

I would consider opening the loudest one up and having a look.

[ch_123]

They're easy enough to open up - just remove the five bolts out of the back and you can pop it open. You need a 5.5mm driver to open them.