[Amps] HB 4-400 amp

Robert woodr90 at gmail.com
Mon Jun 1 21:38:46 EDT 2020


few years ago, bought amp in progress (SK) that uses two x 4-400 tubes.  

The sockets (ceramic type) were mounted on bottom of chassis, no spacing

If there were glass chimneys, those didn’t make it to the auction.

I inserted spacers and lowered the socket ¼ inch thinking to divert some air
over metal base and cool glass better




however the chassis cut for tube is pretty close to tube metal base  &
cooling air path is mostly through the 5 holes in ceramic socket 

5 holes for pins, 5 for cooling air, pressurized chassis with Dayton
squirrel cage blower (similar to Dayton 1TDN6)


although I doubt the motor is spinning at 3300rpm – subjective


The metal base is cool to touch but the glass is hot, too hot to touch

The Eimac spec doesn’t list a chimney as if it’s not needed




any “Cooling” comments or recommendations?  


PS:  My interest in this amp was PS.  Peter Dahl 2400V at 1.5amp rating.
It’s in separate deck and depowered waiting for tubes to fire up and set for
day with filaments on.


73 W5AJ



Midland, Texas


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