New Rig Infant Pics - Any Guesses what it will be?

[N3DRB The Derb]

Hope you used hi temp solder down there, OM. You might get a case of the tube pin drippies.......even tho that STRAP should sink some temp away.

[K1JJ]

Hope you used hi temp solder down there, OM. You might get a case of the tube pin drippies.......even tho that STRAP should sink some temp away.

Yep, good point Derb -

The filament leads are the only ones with heavy current. At the center, they will be carrying 42 amps to each set of 2 tubes and then 21 amps as each branches to the last tube.  The tube pins themselves will be carrying the normal 21A per tube. (at 7.5 V)

I figure the surface area of the copper strap is about like a #6 wire, at least, though it doesn't havre the same density. That may be good for  100A according to specs.  But the big plus factor is the cooling added by the blower moving air under there. 

Just to be sure, I'll run some filament tests with full filament power to see what happens - and leave it on for an hour.

T

[K1JJ]

That filament choke is very cool...So simple....Are those ferrites any special mixture?   How did you test it?...Thanks for the pics..

Hi Steve,

Filament Choke Test:

The choke test is done by running a single wire thru the ferrite cores and then putting a resistor in series with this wire to ground. The resistor value is the estimated input impedance to the GG amp. Mine is about 12 ohms. (4 tubes)

Connect the RF signal generator to the wire on one side of the "choke" and to gnd.  Set the gen to the lowest desired freq, like 1.8mhz.

With a scope, measure across the resistor and then across the choke wire.  (Or across the whole circuit and subtract the resistor voltage) You want at least 90% of the RF voltage to fall across the choke. 10:1 ratio minimum.  The LOWER the input impedance of your amplifier, the LESS inductance the choke needs to be. When operating the amplifier, you want the majority of RF to go thru the tube fil/grid and not thru the choke, so a minimum 10:1 impedance ratio is needed as a rule of thumb.

You can take out some ferrite beads and watch the voltage divide more across the resistor, as a double check.  Add beads until diminishing returns.

I compared this technique to a standard coil-wound bifilar filament choke and could see no difference in performance, ONCE you get enuff ferrite core in there. Mine took only three cores.

I used standard 43 ferrite material with the big cores, about the size of small lemons.  But you can use smaller cores too, as long as the wires can fit thru.  I don't know if saturation is a factor, but since there is filament bi-directional canceling alternating current, maybe there is no threat. Anyone know?

I used this choke method in my other linear amps and it has worked out well for years.  Easy to drive the amps on 160M in GG.

T

[W1RKW]

T,
Build a poor man's manometer out of clear plastic tubing and use it as your airflow/pressure guage.  Then experiment with some small baffle plates underneath. I'd use plexi for the baffle plates because of the insulating property and just hot glue them into place temporarily.  You may be able to tame and equalize the air pressure/flow at each tube.

[Bill, KD0HG]

Tom:
You're building an Orgasmatron?

[W1ATR]

How long are those spacers that suspend the sockets below the deck? To try and balance the airflow, you could try shortening the spacers on the last two sockets to force more air thru the restrictive centers and provide backpressure to the first two closest to the blower.

Looks awesome man! Big glass is King.

[K1JJ]

How long are those spacers that suspend the sockets below the deck? To try and balance the airflow, you could try shortening the spacers on the last two sockets to force more air thru the restrictive centers and provide backpressure to the first two closest to the blower.

Looks awesome man! Big glass is King.

Thanks, Frank -

That's a good idea - to adjust the spacers heights on the farther out tubes..   
I found tonight that after adding the wiring infrastructure, the air evened out a little more, but still needs some adjusting.

My present challenge is to make the plate RF leads as short as possible. Gonna use a lot of copper strap up there too. This long viewing layout is not the best RF layout.

Yes, half the fun is seeing the tubes lite and plates glow. I've always loved 4X1's. Using external anode tubes is FB, but too industrial.
I'll take some more pics once I connect up the fil wiring and fire them up. I may mount a permanent  mirror behind them, since they will be viewed behind a 23" X 25" Plexiglas window.


Bill: I'll let YOU connect YOUR log to the new Orgasmatron first. Let us know how it goes... :-)

Bob - A manometer ... that wud sure take the guesswork out of it. Though, measuring the air flow out of each chimney is pretty easy by using a piece of paper and watching how it floats.  I can see the diff pretty well down the line.

Tom, K1JJ