DC drift transistor pair rubber band turns to acid water !!

[oz2cpu]

if you own this type of generator, please see the end of this video !!
The 3 set of transistor pair hold together by rubber band need your attention right now, else this unit become trash !


https://youtu.be/z_lXRRlShMU

[Nominal Animal]

There have been similar problems – some sort of chemical leeching from one plastic to another; these are probably silicone-based and not natural rubber – over the years.  I don't recall the exact details, but a particular one was slide pouches for use in a binder (maybe 5×6 standard slides per A4), and it turned out that something in the plastic pouch material leeched out or sublimated, and corrupted the slides!

(The main reason I don't buy hobby electronics wire off eBay/Banggood/etc. is not because they're so often copper clad aluminium, but because they for some strange reason like to use overly-plasticized PVA and call it "silicone".  If you keep such wires in a plastic (nylon) pouch, like Aneng 8008 multimeters comes with, depending on the temperature and humidity the plasticizer can slowly leech out and basically fuse the wire to the pouch!)

Wouldn't a soft thermally conductive silicone (like say CHT AS1701) be better than epoxy here?  I'm just an idiot hobbyist, but there must be a reason why they went to the trouble of using a rubber band; it cannot have been the easiest way to thermally couple the transistors together.

[2N3055]

Natural rubber has sulphur in it from vulcanization process.

heat shrink material should be fine..

[oz2cpu]

non compatible plastic types and rubber types
is a real thing, we "old" dudes have seen melt, corode, desolve, many times
when we service old equipment,
it must be an unwanted problem, they just did not know about back then,
it takes many years for this to be a problem

[Fraser]

Many years ago I was warned about denaturing of rubber and it’s ‘desire’ to return to its natural state….oil !

I have seen many Hellerman rubber sleeves degrade and perish but have not seen this “wet” degradation before. Very strange and, as has been said, this is older equipment so the OEM likely did not realise that such would occur over time.

Polyolefin heat shrink tube would be a good substitute for the rubber sleeves. In the old days it was not uncommon to find matched transistors held together with special metal clips but I have not seen them sold in hobbyist retail outlets.

Whenever I see that awful soft ‘rubber’ coating on modern electronics I know that in a few years, especially if hand held, the ‘rubber’ coating with turn to black very sticky Goo ! I had it on tripod handles and it was awful. Thankfully such coatings may be removed with some effort using IPA or other solvents that will not attack the base surface.

Fraser