Jean-Luc Pickguard Posted August 20, 2023 Share Posted August 20, 2023 When I go my Fender Rumble 40 home after buying it secondhand, the first thing I noticed was that the knobs were unpleasantly sticky which did not creat a great first impression of an otherwise great amp. I decided that my microcube better fits my needs for a practice amp, so the rumble is now on reverb. I really don't want the new owner to feel ookie every time they adjust the settings so the stickyness had to go. I appears that the cream knobs on the amp were given a rubberised coating which has broken down causing the stickyness. I thought about trying acetone (nail polish remover) to get this off, but was concerned that this might attact the actual plastic of the knob. I figured that surgical spirit might work so bought a small bottle (£2.19 from superdrug). Wearing latex gloves, I soaked the knobs in a ramekin filled with surgical spirit for 10 minutes, then scrubbed each one with a spare toothbrush and rubbed the surface with kitchen towel. The result is that all of the sticky rubbery gunk has now gone, the knobs are no longer sticky, and importantly this hasn't changed the appearance of the knobs. 2 Quote Link to comment Share on other sites More sharing options...
ezbass Posted August 20, 2023 Share Posted August 20, 2023 I’m going to be the first to say, “Fnarr, fnarr - sticky knob -fnarr, fnarr.” 2 Quote Link to comment Share on other sites More sharing options...
Waddo Soqable Posted August 20, 2023 Share Posted August 20, 2023 Soaking knob in surgical spirit? 😳 Acetone is v. good for removing gunk, but can attack some plastics so needs to be done rapidly Quote Link to comment Share on other sites More sharing options...
Jean-Luc Pickguard Posted August 20, 2023 Author Share Posted August 20, 2023 I did consider acetone but didn't want to risk it eating anything more than the rubbery coating. The other thing I had lined up to try if the surgical spirit didn't work was lighter fluid. 1 Quote Link to comment Share on other sites More sharing options...
Waddo Soqable Posted August 20, 2023 Share Posted August 20, 2023 3 minutes ago, Jean-Luc Pickguard said: I did consider acetone but didn't want to risk it eating anything more than the rubbery coating. The other thing I had lined up to try if the surgical spirit didn't work was lighter fluid. Lighter fluid is always a good one, and less savage than Acetone for sure. Quote Link to comment Share on other sites More sharing options...
neepheid Posted August 20, 2023 Share Posted August 20, 2023 WD-40 is good at getting rid of sticker residue, so maybe it's also good at getting sticky rubber off of things too? Quote Link to comment Share on other sites More sharing options...
itu Posted August 20, 2023 Share Posted August 20, 2023 (edited) That probably was rubber paint. It's really paint in the A: just some sunshine (UV), and it becomes sticky. Acetone sure is very aggressive, butter and oil work for many sticky materials but need quite a long time to act. Edited August 20, 2023 by itu Quote Link to comment Share on other sites More sharing options...
MartinB Posted August 20, 2023 Share Posted August 20, 2023 (edited) Nice! My Rumble has the same problem - I'm guessing that if surgical spirit worked, then meths will also do the trick Update: Works a treat! They don't need to soak for long Edited August 20, 2023 by MartinB 1 Quote Link to comment Share on other sites More sharing options...
Jean-Luc Pickguard Posted August 20, 2023 Author Share Posted August 20, 2023 Excellent! glad it worked for you Martin 1 Quote Link to comment Share on other sites More sharing options...
Baloney Balderdash Posted August 21, 2023 Share Posted August 21, 2023 (edited) 17 hours ago, MartinB said: Nice! My Rumble has the same problem - I'm guessing that if surgical spirit worked, then meths will also do the trick Update: Works a treat! They don't need to soak for long I am not going to waste my meth on cleaning sticky knobs, way too expensive! Though I am curious if regular amphetamine works as well? Edited August 21, 2023 by Baloney Balderdash Quote Link to comment Share on other sites More sharing options...
Waddo Soqable Posted August 21, 2023 Share Posted August 21, 2023 5 minutes ago, Baloney Balderdash said: I am not going to waste my meth on cleaning sticky knobs, way too expensive! Though I am curious if regular amphetamine works as well? Of course it does, you'll approach the task obsessively until its done, and then some... 2 Quote Link to comment Share on other sites More sharing options...
BigRedX Posted August 21, 2023 Share Posted August 21, 2023 This has come up a couple of times with regards to control knobs and there is a good chance that the problem is similar to the one the beset Hercules stands, in that there was a problem with the material used. If this is the case, cleaning with something like acetone will only be a temporary fix, and once the sticky layer has been removed/dissolved the newly exposed material will start to break down in the same way. If its a rubbery coating causing the problem eventually it will all be dissolved away and hopefully whatever is beneath won't exhibit similar problems. However in doing so you'll have lost the advantage of having a grippy coating on the knobs. My opinion is that this is defect that needs to be addressed by the manufacturer by replacing the knobs FoC with ones that don't go sticky. 1 Quote Link to comment Share on other sites More sharing options...
Jean-Luc Pickguard Posted August 21, 2023 Author Share Posted August 21, 2023 (edited) No, this is very different to the hercules issue where the rubbery bit is a thick moulding. The rubbery bit on the Rumble knobs is an extremely thin layer over the hard plastic knobs - like it was painted or sprayed on. Soaking in surgical spirit and giving it a scrub took all of the rubbery layer off. My Fender Mustang GTX guitar amp doesn't have rubbery knobs, so I don't think there's anything lost in not having that layer on the rumble. I bought the amp secondhand, so I doubt fender would have offered any help in my case. Edited August 21, 2023 by Jean-Luc Pickguard 1 Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted August 25, 2023 Share Posted August 25, 2023 Rubber coatings always go icky. I threw a perfectly good radio (except for the ick) away because of it. Annoyingly, the non-rubber one was cheaper. Quote Link to comment Share on other sites More sharing options...
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