Print

[VE7RF]

4CX-15,000A / 8281 Grid driven 80-10M PA.

Originally it had a 4CX-10,000 tube in it, running 5 kw output. With the bigger tube installed, a myriad of changes had to be done. Myself and Scott spent hours on end pouring through the oem schematics. I had to come up with new values, when the bigger tube is used. It has grid and screen over current protection, plate over current loss of B+ and screen voltage protection, loss of airflow protection, below a specified threshold, etc, etc.

Modified from 3 phase to single phase. The input circuit was re-designed, then toss in the neutralization scheme used. 3 x EBM Papst blower's used. Deluxe Magnehelic gauge used, that includes low and high pressure alarm outputs. New screen supply installed, with higher screen V used. A 5 Vdc @ 200 amp SMPS switching supply was modified to provide 6.2 Vdc @ 160 amps CCS. There is still a lot to be done, and currently it is a work in progress. New custom designed and built  plate xfmr is rated for 75 kva CCS...and weighs 900 lbs...and is immersed in xfmr oil.
Enjoy the Video. Later..... Jim VE7RF

https://www.youtube.com/watch?v=QZJeHRXLxII

[KA4DPO]

Interesting but whats the point, unless you want to pay a huge power bill.

Sounds like it will idle somewhere between 6 and 8KW.  By any chance are you buds with VE7KFM?

[VE7RF]

Interesting but what's the point, unless you want to pay a huge power bill.

Sounds like it will idle somewhere between 6 and 8KW.  By any chance are you buds with VE7KFM?

Idles at 8 kw... but only when it's ur time to talk.   It's just a high level experiment, it has no practical use...well maybe for a dx contest.  In winter, it wouldn't cost anymore than heating ur home with electric, but that's semantics.  It would make for a great 75m ragchew amp for 2-4 hrs each night.

 Yes, I know KFM, everybody here in town knows kfm.  The whole fn planet knows who kfm is..including riley hollingsworth..and now Laura smith.   Last time I saw him was pre CV-19.  karol has a TON of cool stuff in his basement.  I bought a nice dahl choke from him.   last time he was at my place was Oct 2016. Same day as when my replacement natural gas hot water tank was replaced. 

[KB8VUL]

So do you know some voodoo to get a 3 phase transformer to run on single phase outside of a phase converter?  I have one out of an old Armstrong 5K AM box that I was thinking about using for a project.  I can build a rotary phase converter for it if needed or just run one of the 3 phase generators when I want to get on the radio with it but diesel is silly expensive right now and 5 bucks a gallon for radio fuel seems dumb. 

Not looking to do anything this big,  just a 3CX3K tube. 

[VE7RF]

So do you know some voodoo to get a 3 phase transformer to run on single phase outside of a phase converter?  I have one out of an old Armstrong 5K AM box that I was thinking about using for a project.  I can build a rotary phase converter for it if needed or just run one of the 3 phase generators when I want to get on the radio with it but diesel is silly expensive right now and 5 bucks a gallon for radio fuel seems dumb. 

Not looking to do anything this big,  just a 3CX3K tube.

In the video, they paralleled all 3 secondary's....and all 3 x primary's.  Single phase 240 vac fed to the 200 vac input tap.  (oem setup had 3 x xfmrs, and was configured for 208Vac,  3 phase).  No phase converter required.  No gen set required.

A cheap approach, would be to use a 5/10 kva pole pig.  A lot of em were 4800 vac..and also had inner taps at 4150 vac.   The 4150 taps would be perfect for a 3x3.  You end up with  5868 no load, then subtract the v drop from the FWB assy, another 22 vdc  =  5846 vdc.  Then a 75 vdc drop across the 50 ohm 'glitch' resistor in series with the B+..... so down to
5771 vdc.  Then whatever drop ur gonna get with a 1.5 amp load.... another 200-300 vdc... depending on filter C used.

Any good 3x3 tube will hi-pot test to 20 kv.   Driven with 200 watts, expect 1.5 amps of plate current...and aprx 5.2  to 5.5 kw pep out.  Correct blower, if u don't have one is a dayton 6DKY9.   https://www.grainger.com/product/DAYTON-OEM-Blower-Rectangular-6DKY9     Puts out 80 cfm @ 1.2 ".  It's the perfect blower for the 3x3 tube.   Tube specs are 67 CFM  @ 1.2"..... when inlet air temp is 40 C  (104 F).