?

Jim:

I wonder... "what if" somebody with way too much money needed 4H, and called one of the xfmr winders and ordered 2x 2H chokes, identical, *but* wound in opposite directions from each other....and ran them in series...?

Wouldn't Kirchoff's Law, or some such crap apply. i.e., the back-EMFs would cancel when the DC flow stops?

It might or might not be possible to make a winding machine run in 2 different directions, I dunno.

Or maybe Joe Junkbox could dig around in the parts pile and maybe find 2 assorted chokes by different mfrs that happened to be wound differently, maybe not identical, but close enough to somewhat cancel the back-EMFs of each other.

Just spitballing ideas.

73

Randy

KZ4RV

On 11/19/2018 2:19 PM, jim.thom@... [ham_amplifiers] wrote:

?

? On paper, the? C-L-C is a superb output filter? for any B+ supply, reducing ripple to low levels.? ?Even with low value caps on either side, and a? ?2-4H? choke used,? it works superb.? ? I tried the? config and the theory works.

Ok, here's the problem.? ?IF the? B+? arcs to chassis, in? the RF deck,? ?or say from? anode to grounded grid, etc, then a huge fault current results.. only limited by the 50 ohm glitch Resistor.? ?2 msecs later, the? HV fuse, located just in board of the? glitch R, opens up.??

Fault current goes from 100 / 134 amps? ( depending on? ?5700 / 7700? config).? ? ?down to? zero....in <? 2msecs flat.? ? The? resulting EMF? from the? 4 H / 127 lb Dahl choke is nothing short? of insane.? ?Like? 10-14 kv.? It also oscillates back and forth in polarity, which charges up / discharges the caps? on either side of the? choke.? ?Current? going into both caps is also insane.? It like ringing a gong..and takes a several seconds to settle down.??

Same deal? ? if a 'normal'? ?L-C? config used, like seen in the old days.? Which explains a lot..like? chokes fried,? excess? B+? onto rectifiers, tube , rf deck, overloaded caps, etc.?

The only fix I can see? working is a HD spark gap across the? choke terminals.?

Jim? ?VE7RF