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Rubbery "Goo" needed to stop capacitors vibrating against PCB

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treez

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Hello,
We fixed our MS519 Digital amplifier and now we wish to replace the 4m7, 80V electrolytics.
We had to scrape the old , crusty glue off when we desoldered the old capacitors......and now the amplifier is buzzing.
Do you know which kind of sealant we can use to hold the capacitors in place so that they dont vibratE against the PCB?
(Preferably something that wont degrade, the old stuff corroded through a component)

What about this?
**broken link removed**
 

I would not recommend that particular silicone. It's acid-setting (releases acetic acid during curing). Might cause corrosion.

What you want is neutral-cure that usually release alcohol instead. Like this one:

https://www.intertronics.co.uk/product/rtv-silicone-adhesive-sealants/

I'm sure Farnell will have something like that. I've used this in small tubes before:

**broken link removed**

Or try this (same as in my first link I think). There are a few at Farnell:

**broken link removed**
 
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FoxyRick is absolutely correct. I've seen the damage first hand.

Regular RTVs which smell like vinegar, will corrode the electronics.
Chip resistors are quite vulnerable, in addition to electrolytic caps.

The damage is many times microscopic, and invisible to the naked eye. But a board cross section followed by an inspection with a good optical microscope will reveal the damage.
 
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Thanks, that must be why the crusty old glue that had been round the electrolytics had actually corroded the bode of a 1N5246B diode away....we only found it was that part because we found an old JBL amp schematic which corresponded.
 

**broken link removed**
This stuff works very well.
 
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Re: Rubbery "Goo" needed to stop capacitors vibrating against PCB

Thanks
The following product from FoxyRick (Thankyou FoxyRick) looks a god price

Servisol Silicone RTV
**broken link removed**

..The datasheet doesnt allure to its rubberyness when cured.

I remember at one place using some stuff they called "liquid rubber", it came in two tubes which were mixed. You had to apply it quickly before it went too hard, but it was still well rubbery.
Does anyone know the name of it?..it mixed to a grey color and i remember one part of it was yellow...but you didnt need much of that part.......i remember we were using it to put in the back of d-type connectors that we had just wired u, we used it as strain relief...it was well rubbery even when cured.

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Thanks Marce,
That Blaktak was what we used to stick thermocuple wires to the PCB so that the metal end was held in place until its thermal glue had cured.
I was never sure if its corrosivenes and acidity was damaging to the pcb's
 

It is used on military aerospace products, that's where I got to know it.
 
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Re: Rubbery "Goo" needed to stop capacitors vibrating against PCB

I remember at one place using some stuff they called "liquid rubber", it came in two tubes which were mixed. You had to apply it quickly before it went too hard, but it was still well rubbery.
Does anyone know the name of it?..it mixed to a grey color and i remember one part of it was yellow...but you didnt need much of that part.......i remember we were using it to put in the back of d-type connectors that we had just wired u, we used it as strain relief...it was well rubbery even when cured.

Two-part RTV... I think Dow Corning do some, or maybe something like this one...

**broken link removed**

Any silicone should have a degree of 'rubberiness'; that's its nature.

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..The datasheet doesnt allure to its rubberyness when cured.

The datahseet for the Servisol 31665 gives a hardness of 30 °IRHD. That's on the soft side for silicones in general. An elastic band is around 25 and a plastic eraser around 45, iirc. IRHD measues the amount of deflection in a sample, it's roughly the 'rubberiness'.
 
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Thanks, Wikipedia is sayign that RTV silicone is a "two component system",

So it does... I think that article is misleading (i.e. wrong).

Wiki's article on Silicone Rubber mentions one part or two part RTV:
https://en.wikipedia.org/wiki/Silicone_rubber
as does its article on Vulcanisation:
https://en.wikipedia.org/wiki/Vulcanization

At the end of the day, RTV just means Room Temperature Vulcanizing (as opposed to vulcanizing at elevated temperature)... nothing to do with how it does that.
 
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Just use a hot melt glue gun.
They seem to work fine for it.

I've often heard that while hot melt glue is fine for temporary mechanical bonding during manufacture, it's not good for long term use.

It can become brittle after a few years, can soften if something gets hot (and the repeated cycling can cause creep and bond failure) and does not necessarily bond well to some solder masks, for example. Despite that it is still used and often 'recommended'. That said, 3M make electronics-specific hot melt glues. Maybe it's just the generic, cheap stuff that isn't suitable.

Silicone is good for twenty years or more.
 
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