>Chris w0ep WROTE:
>Is the 4-400A a good choice for something cheap to start with?
>There seems to be a steady stream of cheap used ones on that internet
>place.
Chris, It's a great starter tube but you really have to be careful
purchasing 4-400 tubes. Many of them are low to no output. Unless they were
guaranteed I wouldn't bother to buy. Those on eBay offering broadcast pulls
usually state that they are pulled during routine maintenance and are
probably good but as always, they are offered AS IS. I bought a couple of
pulls off eBay and both were duds.
I've built two amps using the 4-400A tubes. One 2 X 4-400 and one 4 X 400
amp. I really like the tube and think it equates to a near 3-500Z. With the
screens grounded and cathode driven you need about 100 watts to a pair of
them to get about 1200 out. With 3800 volts DC on the plates and ample drive
I've seen over 1700 watts output from the pair I build but I certainly
wouldn't recommend running them that hard. I wouldn't hesitate to run a pair
of 4-400 tubes at 1500 PEP SSB. They hold up very well.
Larry N5BIP
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