That Johnson 122-275 ceramic socket goes back to the 50's when just about
everything used expensive Eimac forced air flow cooling and the cast
aluminum sockets with chimneys cost more than the tubes. Johnson received an
OK from Eimac for horizontal cooling in their 4-250A/4-400A transmitters and
amps and other companies followed suit.
The SB-220 cooling is well thought out and sufficient as designed. The
problem is builders and other owners who cannot read the manual and dont
place the fan blade at the proper point on the shaft and/or leave off that
small aluminum air deflector on top of the perforated cover. Failure to
clean the blades and lubricate the motor just adds another level of
problems.
The socket uses a rivet to assemble the pin and when the tube pin overheats
that compression bond is weakened. A cure is to gently compress the pin to
original spacing and then use a D-550 or similar gun and a bit of diluted
hydrocholric acid, also sold as plumbers soldering fluid, and flow some
silver bearing solder to bond it all together. Use a toothbrush and the acid
to remove the heat bluing. Flush out the acid residue with a water and
baking soda mix in a spray bottle.
Others may be more comfortable replacing the socket (-;
I dont like the Chinese sockets as it is easy to rupture the tube seal
especially with the older all glass base without the brown compression ring.
Ive heard a few stories of that happening with both versions.
In the hundreds of 3-400/500 amps Ive worked on only a very small number
required replacing the socket which were broken by a users brute force
attempt to restore tension.
Carl
KM1H
----- Original Message -----
From: "Alf Pousar" <alf.pousar@surffi.net>
To: <Amps@contesting.com>
Sent: Wednesday, May 14, 2014 4:15 AM
Subject: [Amps] 3-500Z pin becomes unsoldered
If your solder lugs are dripping the solder due to heath, clean the lug
using a good desolder wick and wrap the wire around and trough the lug.
Then take some small wrapp wire and wrapp around the lug.
Then... solder with high temp ten/silver solder and the problem is gone.
Alf OH2QM
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