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In Reply to: Cautionary tale - Caig ProGold posted by Legendre on January 17, 2005 at 11:45:19:
ProGold is rated for use up to 310 degrees F, which isn't high enough for tubes. A while ago I was told they may have a product for higher temperatures, although I haven't researched it.The Caig website gives the following (contact?) info:
Susan Prenatt, ssp@caig.com or 800/CAIG-123 x112
Follow Ups:
That's pretty darn hot. How hot do you think the pins of a power tube ever get? I doubt they exceed 310F.
I'm sure that 310F is quite possible, I've seen plenty of roasty-looking plastic & micanol sockets over the years. Don't think the 6AS7s ever get quite that hot on the base, tho. Due to the design of a (plastic) octal tube base, thermal coupling from the elements & envelope to the pins is fairly poor, as compared to a miniature tube, or novar/magnoval type.The 6C33C-B is clearly capable of generating some really high temps on the pins, especially the filament conenctions - all of which eventually perish and require reworking / replacement in time.
I'm not sure what properties of the Caig ProGold lead to this particular failure, nor do I know what other circumstances (air pollution, Pepsi Syndrome, etc) may have worsened the situation.
If I had to guess, I would say that the failure was a product of heat, time, and excessive application of the product. An interesting clue is that it was the filament connections which showed trouble first. This is a relatively high-current (2.5A) connection, and once even the slightest resistance is introduced, the snowball effect begins:
Small resistance in the connection creates heat, which further degrades the connection, which results in even more heat, which results in even faster degredation, and so on, till it fails.
One thing that I am curious about, is the dilectric property of the stuff. Some compounds do not react well when exposed to moderate-high potentials - the absolute highest potential seen on a 6AS7 socket in an Atma-Sphere amp is about 215V dc in normal operation, and 315V dc at initial turn-on. I wonder if these moderate voltages have any effect on the ProGold product..
You may be right - my memory isn't so good, but someone had mentioned that Caig has a product that's supposedly OK for use on tube sockets. Maybe they've changed the formula. I'm still leery about using it, though.
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