[Boatanchors] 4-400 tube replacing a 3-400z for circuit test

[david freeman]

I've used 4-400 in place of 3-500 and it works, sort of.
The input impedance is different and it messes up the tuned input.
My amp didn't have enough input adjustment to compensate.
That's assuming that the Swan has tuned inputs, but I'm not familiar with it.
If you have a transceiver with a tuner built in that should help matters.
I don't remember exactly, but after adjusting, the SWR was high, but not ridiculous.
I, like you, was only interested in testing things out, not operating that way.


YMMV
Dave, WW8S

> ----- Original Message -----
> From: "Greg Mijal" <bluebirdtele at earthlink.net>
> To: boatanchors at mailman.qth.net
> Subject: [Boatanchors] 4-400 tube replacing a 3-400z for circuit test
> Date: Thu, 14 Dec 2006 16:12:29 -0700
> 
> 
> Hi:
> 
> Has anyone used 4-400's in a made for 3-400Z's amplifier?
> I have a Swan MK 1 amplifier built for two 3-400Z's and no tubes.  
> I do have a set of 4-400's.  The necessity of this is to evaluate 
> the amplifier overall circuit, not necessarily "Convert" the amp.
> Anyone do this one before?
> Thanks
> Greg
> WA7LYO
> in sunny Feenix
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