Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: LooseChange on March 12, 2011, 04:01:24 pm
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I see glue on many large parts on circuit boards. What's good for resistors that get hot to keep them from vibrating??
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RTV form-a-gasket. Available at your flavorite auto parts store. If that resistor gets hotter than an engine, you need a higher wattage resistor. I try like heck to not glue parts although we've discussed the Aggie Dumble...... clear epoxy. :icon_biggrin:
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wot buttery said.
If the parts are likely to vibrate, I don't use glue (glue is sooo tacky :laugh:) I use proper support mounts and cable ties - looks neater/ more-workmanlike and is easier to dismantle than glue.
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I see that glue on the ceramic resistors at times in SS amps. And electrolytic capacitors as well. I use the big hotglue sticks for the caps and the resistors i leave alone. I figure if i have the resistors real tight when i pull the leads through the board and solder them they are going to be fine.
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I would think a resistor would stay cooler if all four sides (assuming rectangular here) are exposed to air. Using the board as a heat sink doesn't appeal to me.
Axial components don't worry me except for BIG electrolytic caps. Components with radial leads, OTOH, would worry me more. I've taken to using Zip ties for B+ filter caps on the theory that they will require replacement someday.
Having seen the density of LC's circuit boards however, I completely understand the basis for his question. R-T-V ought to do the trick. How hard would it be it remove in the future though?
Advice worth the price :wink:
Chip
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I use a little shot of RTV and then cable tye,s but I only do that on large resisters, I only started doing that when i put my head in an amp stand and let someone play my marshall at very loud level everything vibrated I was amazed big caps were the worst. :think1:
Man I love these things. :l2:
Thanks Bill
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Hey Bill,
:hijack1: How about this one..... :m13
Brad :m2
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And here I thought he was talking about his love for amps! :guitar1
Chip
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And here I thought he was talking about his love for amps! :guitar1
Doh! :w2:
Brad :laugh:
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On radial caps (the only ones I secure), I hook one of the leads, apply a small dollop of silicone on the bottom, stick it down (the hook is usually enough to hold it in place), and let it dry overnight. It's true about the electrolytics having to be replaced eventually, but I don't cable ties do much against vibration.
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Gaz's got a point about cable ties not doing much to prevent vibration. I was thinking more in terms of the amp being dropped, bumped, tipped over, etc. Need some RTV for a totally unrelated project anyway...
Cheers,
Chip
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What is used to "glue" a part down depends on what part and if it's a solid state amp or tube amp and what the component is . for cap's on a solid state amp you can use a hot glue gun ( many manufactures do) on a tube amp RTV is better, however if it is a axial lead cap the addition of a zip tie is a good idea (if possible) radial lead well glue down and hope for the best. Large resistors I hook and solder , I generally don't glue these. Transistors glueing down is a bad idea , as with most semiconductors. Relay's go for it hot glue, RTV whatever ya want to try and peel of the board later. To sum it all up , you can use just about any nonconductive adhesive.
Rock On
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Hey Guys, I just came across this in another forum. If you're using RTV, make sure you get "Electronics-Grade RTV".
It seems that some RTV can corrode copper as a result of the curing process.
Refer to this article for the full story:
http://www.edn.com/article/517356-Acid_test.php
Here's an excerpt:
A little research revealed that, as some RTV adhesives cure, they release acetic acid, the same stuff that’s in vinegar. And acetic acid corrodes copper. In this case, the adhesive and wires were trapped together in a sealed environment, making the corrosion even worse. After some consultation, the adhesive vendor recommended an electronics-grade RTV, which would cure without releasing acetic acid.
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What's that clear goop Fender puts under those 470r - 5W resistor on all the Hot Rod type amps? These get very hot.
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If it's kinda soft and rubbery it should be silcone? If harder should be hot melt glue?
Brad :think1:
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A little research revealed that, as some RTV adhesives cure, they release acetic acid, the same stuff that’s in vinegar. And acetic acid corrodes copper. In this case, the adhesive and wires were trapped together in a sealed environment, making the corrosion even worse. After some consultation, the adhesive vendor recommended an electronics-grade RTV, which would cure without releasing acetic acid.
I belive it's in silcone to, sure smells like it.
Brad :icon_biggrin:
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Okay. So what is the brand name of this stuff. Where do I get it? Thanks!
EDIT... The silicone gel is what I'm after.
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I do some sub-contractor work for a very awesome pro-audio company, we use Momentive RTV 102 on pretty much all the caps but none of the resistors. It helps with microphonics.