I’ve been powering up some of my old QRP gear to see if any of it still works. The gear has been stacked up on a shelf above my operating position for years. In testing some of this gear, I came across a curious problem.
Last night I was rearranging some of my equipment and re-routing some coax cables. When I went to move my Oak Hills Research power meter, it was stuck to the shelf. The rubber feet on the bottom of the meter had become slightly soft and sticky. I didn’t think too much of it at the time. I just finished connecting the cables and placed it back on the shelf.
Today, I took my old MFJ-9030 transceiver down from the shelf and was greeted with a gooey mess. The rubber feet had completely dissolved and turned into a sticky, tar-like mess. Using a single-edged razor blade, I scraped off as much as I could from both the radio and the residue on the shelf. I used some mineral spirits to clean up as best I could. The mineral spirits worked great, but I still had sticky spots where the feet were attached to the radio. I cut some pieces of aluminum duct tape to cover those spots, and I applied four new feet from my junk box.
My theory is that the rubber (or whatever material they are) feet reacted with the finish on the shelf. I know that vinyl guitar straps and accessories can damage the lacquer finish used on some high-end guitars (like my 1973 Martin D35 acoustic), so I suspect something like that happened to my radio equipment. I built the shelf and my operating table from some repurposed shelves that were in the house when we moved in back in the late 70s. So, I have no idea what kind of finish is on them.
Besides the power meter I mentioned earlier, it looks like my old MFJ-941-E antenna tuner is also affected. So, I’ll have to replace the feet on those items and clean up the residue on the shelf with the mineral spirits. Needless to say, some of this equipment hasn’t been moved in years.
This wasn’t exactly how I wanted to spend my afternoon, but I’m glad I spotted the problem.
72, Craig WB3GCK
WB3GCK QRP Amateur Radio 
Same thing here. I used Gamsol to completely remove the mess. I
wonder if the rubber did not have stabilisers in the feet forming
compound as the feet on my power supply rests on a solid Arborite
shelf.
Cheers
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I also had the same issue with a Vectronics HF tuner. It had been sitting in a box for a decade or more when I recently opened the box, the rubber feet “melted”, there was residue on everything those feet touched. IPA cleaned it up perfectly. The same thing happens with rubber belts in disk drives and cassette tape mechanisms which have rubber belts.
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Craig, I experienced the same problem with the rubber grip band around the tuning knob of some old transceivers. I suspect the rubber wasn’t made the same way 40 years ago.
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The “rubber” turning to goo is from hydrolysis – typically from urethane rubber breaking down – often seen not only on rubber feet, but belts, grommets, pinch rollers and footwear. This doesn’t usually happen with “natural” rubber.
This can seemingly occur rapidly once it starts. There’s really nothing to be done about this other than vigilance and pre-emptive replacement – unless you want to keep the object in cold storage.
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I noticed a brown streak running down the wall from a corner of a picture that’s been hanging in our living room for more than 20 years. A google search revealed that this is not unheard of in the picture framing world. The rubber bumpers on the backs of the pictures are the same thing we use for feet on projects.
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The rubber used in belts and footpads from this era is a mess now. I have VCR’s and turntables from the 90’s and the belts and drive wheels have turned to goo. Seems the rubber used for belts and pads of all kinds from the 90’s just becomes tarry messes after this long. These belts used to be found all over but anymore they are hard to find.
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Goo-Gone is what I use to remove sticky residue, Craig. Works great and you can find it at most grocery stores in the cleaning supplies aisle.
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