Re: Filament help!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Mitchell" <Wrenchead-at-starband-dot-net> 

Does anyone know where I can get a 5v 6.5A tranfo online?  Mouser has 5v 8A
tranfo's but they are like 30$ and thats ridiculous.

Regards - Jim Mitchell
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, October 26, 2003 8:34 AM
Subject: Re: Filament help!


 > Original poster: David Speck <dave-at-davidspeckmd-dot-org>
 >
 > Jim,
 >
 > 5 volt, 6.5 amp filament transformers are not very hard to find at
hamfests.
 >
 > You definitely would not want to use a PC PSU -- too many sensitive
 > components in the switching power supply section to use in the vicinity of
 > HV RF.  You don't need DC for a filament supply, anyway.
 >
 > You can make a custom filament transformer for next to nothing by removing
 > the high voltage secondary from a small scrapped microwave oven
 > power  transformer, and winding about 5 turns of 12 gauge wire in its
 > place.  There is already a filament winding on most MOTs that may be close
 > to the voltage that you need.  You might improve its efficiency if you
 > knock out the magnetic shunts between the primary and secondary windings.
 >
 > Can't comment from experience on the relative suitability of the tubes,
but
 > I suspect that the 4-125 is the more robust tube.
 >
 > HTH,
 > Dave
 >
 > >I'm using a 4-125A in my VTTC, and I cant find a filament supply!  I was
 > >thinking of using a PC PSU but they have too many wires and I don't know
 > >which ones to cross for power on, and which to load to keep regulation
 > >proper.  The 4-125A needs 5v at 6.5A for the filament.  Also, any idea if
 > >thise tube is better than the 813? I have both and am wondering which I
 > >should use.
 >
 >
 >
 >
 >
 >