Silicone to mount filter caps???

Discussion in 'Shock Brother's DIY Amps' started by King Fan, Jul 22, 2019.

  1. King Fan

    King Fan Friend of Leo's Ad Free Member

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    I’ve seen experts suggest RTV silicone to secure filter caps in place. I’d like not to drill new holes in an old amp I’m restoring, and terminal strips would mean new holes. Also space is super tight.

    I know there are other ways. But would silicone hold OK? Painted chassis, shiny F&T caps, any issues? Any experience? Other problems you see?
     
  2. Phrygian77

    Phrygian77 Tele-Afflicted

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    I use Alex Plus, same thing my friend uses to glue down crossover components in his high-end hi-fi speakers. The only problem is the temperature rating, so inside the chassis near tube sockets might not work out so well. I haven't had any issues using it in the dog house.

    I think silicone is fine, but you want a type that doesn't have corrosive outgassing as it cures.
     
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  3. Phrygian77

    Phrygian77 Tele-Afflicted

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  4. King Fan

    King Fan Friend of Leo's Ad Free Member

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    Thanks, Phryg, that’s excellent.
     
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  5. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Yup - I do it all the time. Follow the corrosive advice and make sure it's specifically advertised as being non conductive.
     
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  6. sds1

    sds1 Tele-Afflicted

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  7. dogmeat

    dogmeat Tele-Afflicted

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    or hot glue
     
  8. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Hot glue is often not sticky enough to really grip a chassis, in my experience.
     
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  9. charlie chitlin

    charlie chitlin Doctor of Teleocity Silver Supporter

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    Silicone, BTW, is rated to 400deg...but I'm guessing it handles more.
    I used it at the exhaust ports on Harleys for years, and it never gave in to temperature.
    I would also imaging that any corrosive outgassing would only happen during curing.
    I've never seen any sign of your basic hardware store silicone causing corrosion.
     
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  10. King Fan

    King Fan Friend of Leo's Ad Free Member

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    Thanks, very helpful.

    If I'm looking right, it helps to search for 'non-corrosive RTV silicone', since the ordinary stuff is corrosive (mild acetic acid?) at least during cure. OTOH it *seems* like most silicone is non-conductive, and the conductive stuff (copper-infused, eg) seems to be a specialized product. I see many of these products are rated to at least 204°F continuous, which I guess oughta be OK unless you're working right next to a tube or the PT.
     
  11. King Fan

    King Fan Friend of Leo's Ad Free Member

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    Aha, Charlie, we were posting at the same time. In my research, even the most common RTV silicone seems rated to 204° continuous, but in the automotive section you can find products rated to 400°F, and others (Permatex ultra red at my store) even rated to 600°F.

    I like your reasoning about corrosion. I probably wouldn't put 'corrosive' silicone on PCB traces, copper, maybe aluminum? I bet you're right that it won't do anything to plastics, urethane, enamel, etc. Steel? Who knows, but some sources do support what you say about 'the cure being the disease' (to coin a phrase).
     
  12. VintageSG

    VintageSG Friend of Leo's Ad Free Member

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    You can get stand-offs with self adhesive bases that allow you to secure wiring/caps with tie-wraps. The decent ones use adhesives from companies like 3M and Scotch. One fitted, they resist most attempts to remove them.

    ziptie.jpg

    Non-acid cure silicone does a good, if slightly messy job too.
     
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  13. King Fan

    King Fan Friend of Leo's Ad Free Member

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    Thanks, yeah, I actually have one (though I'd need like 3 or 6 here). And those would be a most practical solution.

    It's just I figured nylon ties in a 50's amp would look a bit off, and I'm vain -- I can't bring myself to cover up any shiny black and gold on F&Ts.
     
  14. D'tar

    D'tar Friend of Leo's

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    separating the caps (no multi section firecracker) would allow one to place the filters wherever you like. PTP style with the 20uf right at p2 of 5y3, 10uf at OT B+supply tap and 10uf right at the plate of the pre tube. Assuming this is a GA9 :) Some spaghetti tubing, nos cloth covered wire and bobs your uncle.
     
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  15. strat a various

    strat a various Friend of Leo's

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    Hot glue melts when it gets hot ... is the problem.
     
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  16. tubedood

    tubedood Tele-Meister

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    was wondering the same and went with the hot melt glue... I tried the white and clear and I liked the look of the white one better. I haven't had an issue with it getting that hot during use. I am all ears for a better suggestion!

    Melt glue.jpg
     

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    Last edited: Jul 22, 2019
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  17. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    See, I think that's the perfect purpose for hot melt. You have a nice surface to secure to with a confined area. But for straight to chassis, it's silicone all the way.
     
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  18. Bill Moore

    Bill Moore Tele-Afflicted Silver Supporter

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    Being in the automotive business, we use silicone a lot! Since the addition of electronics to vehicles, we've been cautioned to use only "sensor safe" products, so that's all I buy, (and I've used it on a few SS amps that had what appeared to be "hot glue" holding the caps down/together).
     
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  19. King Fan

    King Fan Friend of Leo's Ad Free Member

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    Yeah, it just might be a GA9. :)

    You're right, keeping each filter cap in its own sector is super sano, and keeps leads short. And it's especially logical for classic PTP. Or for a 'logical-layout' board a la Doug Hoffman (note the three filters under the pots).

    caps.jpg

    I've been looking for some way to do this ever since I saw Doug's helpful list of filter cap solutions. Sadly the little GA9 isn't quite that roomy, and the PTP tie points are already clobbered with solder and buried under their wiring. But since the chassis is so tiny, I'm gonna use your idea a different way, retaining the existing input leads to the filters, but splitting their grounds. At least I think that's what I'm gonna do... :D
     
    Last edited: Jul 22, 2019
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  20. King Fan

    King Fan Friend of Leo's Ad Free Member

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    I see even the 'low-temp' variety of hot glue melts at 248°F, so probably OK from the temp angle unless you're trying to glue stuff to your tubes. :D

    But y'all got me wondering: How hot *does* it get inside a (tube amp) chassis? Obviously it's hotter right by the PT and over the hotter tube sockets, but even on average? Anybody have any data?
     
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