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Author Topic: new amp project 4CX250B's  (Read 33659 times)
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ke7trp
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« Reply #25 on: December 10, 2009, 10:51:32 PM »
Maybe.. Good point though!  I have some in the bags still.  Old MIlitary metal/ paper bags. I am sure those are good. 


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Ralph W3GL
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« Reply #26 on: December 11, 2009, 03:41:58 AM »
Thanks Jay, for the schematic, very interesting set-up.

Important point with the 4X150 and 4CX250B is to run the filament AT or slightly
below 6 volts.  The cathode "boiling" problem is caused by over voltage here...

Most hams just grab a standard "6 volt" filament transformer and never bother
to look at the voltage at the socket!
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73,  Ralph  W3GL 

"Just because the microphone in front of you amplifies your voice around the world is no reason to think we have any more wisdom than we had when our voices could reach from one end of the bar to the other"     Ed Morrow
ke7trp
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« Reply #27 on: December 11, 2009, 10:39:43 AM »
Yes..I was going to post that..  They run them at 6.3 or higher.. It toasts the tube.  6.0 is suggested and down to 5.5 if you have lots of disipation going on.. Like in an SSB amp.  I understand they last for years and years if you lower the Fil.


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