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RE: Permatex Clear RTV Silicone Adhesive (and more!)

"Actually, I've simply affixed various..."

Oh, I know. But isn't it sort of neat to know that you are using the very stuff that the aerospace industry uses, or at least used to, for the same thing?

In the same 'transfer of technology' vein there is a technique that we used to use to reduce microphonics that is directly usable inside audio gear. It seems, looks and is sort of kludgy, but it works very well and costs very little.

It consists of using strings of epoxy to attach components to one another, especially their "free" end away from the PCB if there is one. It accomplishes two things, parts whose stray field interactions may be modulated by shock and Vib. are held quite rigidly WRT one another and the added dimension of support reduces the resonance of the individual parts. Here's how you do it...

Needed: White epoxy (the stuff that cures hard), we used to use Hysol epoxy-patch, a hair dryer, toothpicks.

Using a toothpick mix up a little epoxy, maybe 1/3 tsp, on a piece of paper. Then warm it up with the hair dryer and stir a little more, the viscosity will go way down when it warms up. Then pick up a little dab with a toothpick and a slight twirl, touch it to the top of a part and drag the thread to the next part. Then get some more epoxy and do more. The pot life of the warm mixture is only a minute or so and you can use it a little longer by heating it up some more. Since the epoxy is warm when you apply it it will harden to the touch in just a few minutes. Depending on how much you have to do it may take several batches but once you get a feel for the process you will be able to do quite a bit with each batch. When you get done it should look like a demented spider has been loose in your gear.

If you want it to seem like a coherent spider did it, keep the functions apart. For instance keep the oscillator stuff grouped separately from the power supply or output stages.

Usually there are only certain areas that really need it and they might be revealed by tapping around with a stick (unsharpened wooden pencils work) while listening with headphones or watching with a scope. You can't use a spectrum analyzer as it averages out impulses.

You don't have to use a lot to be effective. If you need to remove it to change parts just hit it with your soldering iron for a few seconds and it crumbles.

Regards, Rick


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  • RE: Permatex Clear RTV Silicone Adhesive (and more!) - rick_m 10:36:09 09/17/11 (0)

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