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Author Topic: C-37A Tube Dampener/Holder Material  (Read 777 times)

Spindrift

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C-37A Tube Dampener/Holder Material
« on: December 26, 2020, 12:53:41 PM »

I'm trying out some tubes in my C-37A mics and have come across this interior piece which appears to be a tube dampener. I've attached a picture of the part.  It seems like the orange material may have, at one point, been soft rubber. I suspect due to age and the heat of the 6au6 tube, it has hardened into a plastic like substance.

I doubt these parts are fresh and available from Sony any longer. I was wondering about the option of fashioning a small appropriately proportioned hi-temp RTV silicon gasket in the place of the hardened orange puck.

Have you C-37A techs & owners come up with any viable alternatives or should I even worry about this?

Thanks,
Keith

EDIT: According to Wikipedia, it appears that RTV is corrosive to electronics:  "Acetoxysilane-based RTV releases acetic acid during the curing process, and this can attack solder joints, detaching the solder from the copper wire."  Do you know of any alternative gasketing materials that don't release acetic acid (that vinegar smell)?
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mbrebes

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Re: C-37A Tube Dampener/Holder Material
« Reply #1 on: December 26, 2020, 02:52:35 PM »

I think it acts as a retainer rather than a dampener.  Probably there to keep the tube from working loose from the socket.  I don't think you should worry about replacing it.
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RadarDoug2

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Re: C-37A Tube Dampener/Holder Material
« Reply #2 on: December 26, 2020, 03:22:12 PM »

You could probably find a standard grommet to replace it. Check places like Digikey and Mouser.
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Spindrift

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Re: C-37A Tube Dampener/Holder Material
« Reply #3 on: December 26, 2020, 05:03:33 PM »

With the part installed on the mic, it doesn't appear that the old grommet is making contact with the tube. I'm not sure if that's due to shrinking from of age or if it's by design. If I can determine that it was designed as some sort of cushion to help dampen tube microphonic, then I might hunt down a new grommet or fashion some sort of silicon gasket replacement.

Thanks for the suggestions.
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klaus

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Re: C-37A Tube Dampener/Holder Material
« Reply #4 on: December 26, 2020, 05:52:02 PM »

Two functions for the rubber retainer:
1. keep he tube seated and centered
2. minimize external vibrations and their transmission into the tube as interference

As long as the replacement chosen provides both functions, it does not matter what damping material you  use. Heat is not an issue in this cathode-follower circuit.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

RadarDoug2

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Re: C-37A Tube Dampener/Holder Material
« Reply #5 on: December 26, 2020, 06:30:38 PM »

It should sit over the pointy bit on the tube and just touch it.
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