[R-390] (no subject)

[Barry Hauser]

Hi Miles

That's interesting.   Could it be they had another reason for going with the 
tan, mica-filled Bakelite -- less likelihood of cracking or something?  It 
would seem that at least the sockets for the 6082's would be candidates for 
ceramic considering the heat factor, and possibly also those for the 
rectifiers.  I don't recall if I've ever seen them there.

Odd parallel:  I just had some temporary caps (not capacitors) installed at 
the dentist.  I complained that they felt rough, not slick like previous 
acrylic "temps".  The dentist explained that it's quartz-powder-filled -- to 
provide additional hardness and resistance to wear, not heat resistance, 
though it probably does that, too.  Of course, another material -- used for 
permanent crowns -- is usually porcelain (ceramic).

He's got a lot of stuff that would be handy in repairing small parts, 
replicating knobs, etc.  Unfortunately, the fee would be a tad pricey --  
unless, perhaps I can infect him with VRV -- Vintage Radio Virus.  (not 
likely, though)

Barry

----- Original Message ----- 
From: <k2cby at aol.com>
To: <r-390 at mailman.qth.net>
Sent: Saturday, July 09, 2005 9:56 AM
Subject: [R-390] (no subject)


> In general, ceramic tube sockets were considered "top of the line." In 
> addition to being used in high-voltage, high-power and high-heat locations 
> (ie most transmitter final amplifiers), they were also used in oscillators 
> for maximum stability because the capacitance between pins changed very 
> little with temperature. My own 390A has none, and I have not seen any in 
> the odd 390A modules I have picked up over the years.
> "Second best" are mica-filled Bakelite. These are the medium-tan colored 
> sockets used throughout the R-390A. They were standard for low-power RF 
> use.
> "Third best" are the injection molded black Bakelite sockets. Although 
> these are below "standard" for the R-390 and R-390A, they are certainly 
> suitable for any of the audio stages, the VR tube and the rectifiers. They 
> are not recommended for RF.
> Last of all are the flat "wafer sockets" made up of two layers of phenolic 
> sheet material. These were pretty much confined to cheap, mass-produced 
> consumer products, but the military did use this type of construction for 
> vibrator sockets and battery connectors.
> Miles Anderson, K2CBY
> 16 Round Pond Lane
> Sag Harbor, NY 11963
> k2cby at aol.com
> _____________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/faq.htm
> Post: mailto:R-390 at mailman.qth.net
> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
>