De-Vulcanisation, A.K.A. Rubber Rot

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Most long-time audiophiles would be familiar with the issue of speaker surrounds going crumbly and falling to bits but few really understand why this occurs. Decomposition of rubber components does not just affect speakers however. Many amplifiers use rubber mounts for components like power transformers. This Audio Research solid state amp provides us with one extremely mucky example!
The unit had been stored face up, resting on its rear handles. The transformer is mounted just behind the front panel with a big slab of vulcanised rubber in between. The rubber was well on its way to reverting to a liquefied state and gravity was helping it ooze all the way from the front to the back as can be seen from this shot of the inner surface of the bottom panel.
It was clear from the start that saving this amp would involve pulling it all apart... but the more it came apart, the worse it looked. This is very thick, nasty, sticky, smelly goo that turns anything it touches black. Its consistency is somewhere between that of hot tar and cold treacle!
The sub-panel had to be prised away from the transformer to reveal the source of this evil muck. The cleaning effort was slow and painstaking and involved a lot of cleaning materials and chemicals.
An hour or so later and we're almost down to the metal but there's at least another roll of paper towel and sticky goo remover to go before the transformer can be re-mounted.

Vulcanisation is a process that produces tough rubbers for all sorts of industrial and automotive applications. It involves the formation of molecular bonds between latex and sulphur to form very long chain polymers. Sooner or later however, these bonds will start to break down thanks to either oxidisation or bacterial action or both. How long this takes is not very predictable and no doubt environmental factors would also affect the rate of degradation. This is precisely the same mechanism that causes speaker surrounds to break down. Bottom line? If you see any rubber bits on your gear getting a bit soft and sticky, don't delay getting it checked out because it's a lot easier to remove old rubbers while they're still in one piece.

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