Sony VFET Amplifier Part 2

Like Nelson said they look like Beryllium Oxide. They can be a little brittle so careful tightening them but I don't think anything beats them for low thermal resistance. I think I saw a statement that they conducted heat better than aluminum. Back in 1977 I think they had a retail price of about $ 3 each !
 
Beryllium Oxide is a ceramic.
Beryllium Oxide is an excellent conductor of heat, yet it is an insulator electrically.
As Nelson has mentioned though, it is VERY TOXIC if particles (as dust or smoke) are inhaled.
If it is B.O.(sometimes named Berlox), DO NOT break, or grind, or sand or modify it in any way that could release any as dust particles which could be breathed in.
It's manufacture is highly regulated in the USA and has been nearly put out of business because of it's waste byproducts.
Do not let your children play with any B.O. products.
Safety First.
Know what you are dealing with !

Best Regards
 
Wow - a whole bag full of unobtanium! When I first started looking into insulators about 15 years ago, Beryllium Oxide was listed as having the best thermal characteristics and had long since been banned from sale. Do pay attention to what others have said concerning breaking, scraping, or any other activity that produces dust or particles.
 
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Or they could be regular type ceramic. I have some ceramic insulators that aren't BeO and they look just like that- white ceramic, but their heat transmission is nowhere as good..So I guess we just don't know, so have to err on the side of caution
Wow - a whole bag full of unobtanium!

Not trying to liquefy the dust, discussing how to remove that old grease or whatever on them, without scraping.
 
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Or they could be regular type ceramic. I have some ceramic insulators that aren't BeO and they look just like that- white ceramic, but their heat transmission is nowhere as good..So I guess we just don't know, so have to err on the side of caution


Not trying to liquefy the dust, discussing how to remove that old grease or whatever on them, without scraping.

Large difference in thermal conductivity between BeO and Al2O3
BeO 260 W/mK
Al2O3 36 W/mK