[Amps] HB 4-400 amp

[Robert]

SK-400?

interesting, the data sheet on 4-400 Tube didn't have that great info.
THANKS!

73 W5AJ

Robert
Midland, Texas

-----Original Message-----
From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Rob Atkinson
Sent: Tuesday, June 02, 2020 9:58 AM
To: amps at contesting.com
Subject: [Amps] HB 4-400 amp

You need to read Eimac document SK-300A Air System Socket.  It will give you
the socket and chimney for the 4-400A among other tubes.  You need the
SK-406 chimney.  Lowering the socket a bit is okay but you
may need to file out the chassis holes some.   I was the photo of the
tubes.  Obviously chimneys were there once because the clips for holding
them are there.  Get a pair of SK406s and put them over the clips and
reattach the anode heat sinks and you should be fine.  You need real SK-406s
because they are shaped to force air on to the heat
sinks and are the right height.   Running the tubes with only air on
the pins risks having the bulbs get too hot.  It's possible for the vacuum
to suck in the glass if it gets soft.  Tube glass is pyrex but it can melt.

73
Rob
K5UJ
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