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Author Topic: What type of material is used to insulate between electrolytic capacitors?  (Read 2534 times)
KU4UV
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Posts: 376




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« on: January 11, 2013, 03:42:27 PM »

Hello everyone,

I have an old C.B. radio that is about 35 years old that I am recapping.  I have a question about what type of material is usually used to insulate electrolytic capacitors from one another on the circuit boards to prevent them from shorting?  Some of the capacitors on the board are so close to each other that they had some sort of material between them to prevent them from shorting.  I have no idea what this material is.  Couldn't you just use hot glue or something like silicone or RTV sealant between the capacitor bodies?  Anyone know what might be used to insulate capacitors, and where I could find some of the material?  Thanks!

73,
Mike KU4UV
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N4ATS
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Posts: 851




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« Reply #1 on: January 11, 2013, 04:01:16 PM »

That is exactly what it was intended for , I worked for a CB manufacturer way back (Hustler Antenna who also made CB's and case tractor radio's for various lines) and the glue was actually to keep the caps on the board during the wave solder flow machine as well as keeping them in tact under vibration. Hot glue will work just fine...
« Last Edit: January 11, 2013, 04:04:02 PM by N4ATS » Logged
N4NYY
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« Reply #2 on: January 11, 2013, 04:19:41 PM »

I cannot see how caps can short together when flush with the PCB. As N4ATS said, it was likely mobility and manufacturing reasons. It does not matter if the caps are touching each other. So long as the leads are not touching each other. The glue serves no insulating purpose.
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KU4UV
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« Reply #3 on: January 11, 2013, 09:53:06 PM »

Thanks guys!

73,
Mike KU4UV
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KD0REQ
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Posts: 1050




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« Reply #4 on: January 15, 2013, 03:43:12 PM »

electrolytic capacitors in singles are encased in PVC shrink tubing with the specs printed on it.  as long as the material remains intact, it is supposed to be enough insulation for the cap's rated working voltage.  if you have reason to not trust that the board traces and sleeve are inadequate, use a stripe of glue to both hold the thing off the board and insulate it.  heck, wax will work.

most everything else now is cased in epoxy for stability and moisture resistance that will hold off voltages above the rated.
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AA4HA
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« Reply #5 on: January 17, 2013, 07:41:52 AM »

On a metal can electrolytic capacitor that should be at ground potential. If they are being used for simple power supply applications they all are probably attached to the ground rail.

When you use a bunch of caps in series (like on a high voltage power supply) the cases can be at different potentials.

I would look at the traces or get an ohmmeter and check. I bet the cases are all connected to the - pin and that goes right to ground.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
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