[Boatanchors] Re: GB> 4-400 tube replacing a 3-400z for circuit test

[Bob Roehrig]

On Thu, 14 Dec 2006, Greg Mijal wrote:

> 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

Ground the screen grid pins (I think pins 2 & 4). I am running 4-400's in 
my modified Johnson Desk KW that way in G-G. Just make sure you don't 
exceed max screen grid current. The other problem may be if that amp uses 
chimneys, the 4-400's may be too tall to fit the chimneys.



                               Bob Roehrig
                     Aurora University    Telecom dept.
                            broehrig at aurora.edu
                          K9EUI  W9ZGP  WD2XSH/19
                     630-844-4898      fax 630-844-4222
                     "Nostalgia is a thing of the past"