Made the big haul today! Couple of Questions...

[N8UH]

Drove to AZ today to pick up my goodies from Dennis (Thanks!)
As you can see in the pic, it was a lot of big, heavy stuff. Mod and plate trannys, mod reactor, 4X1s, etc. Plenty of stuff to keep me busy for a long time!

Got the iron into my shack, where it will rest for a while until I get things going. I tested the Mod Transformer and it's a 1.4:1 turns ratio or 2:1 impedance step-down if I did things right. So now it's time to start figuring things out modulator-wise. Looks like 833s or 4-400s could be in my future!

Then I tested the plate tranny, but got a bit confused. There is the assortment of taps between 208 and 245V. I get that - different line voltage taps. Then there is a tap with a "0", and another with "CB" I put 24VAC through the 0 and 245V taps and got 340VAC out. Wondering what the CB tap did, I put the same 24V through it and the 245 tap, and got 240V out. So the voltages would be 3400 and 2400 out respectively. The question is, what is the CB tap, and what is the 0 tap? Which one is the "right" one to use as a common, or is there a right one at all???

Thanks!

[n2bc]

Just a guess...   CB = CutBack   or the low power setting on the original TX.   Wring it out with a good ohmmeter.

[sndtubes]

With an input of 208 VAC, it sounds like it might be a 3 phase transformer.

[W3SLK]

Could it be that "CB" stands for 'Common Bond'?

[W7TFO]

N2BC got it right.  It is the tap used for power cutback. 

It was fun getting the mod trans out of our ride into his, 300+ pounds!

QRO a GO GO.

73DG

[K5UJ]

Whoo hoo!  Don'tja just love big parts?    

Re: the 0 tap, the answer that is, what to do with it, depends (obviously) on whether it's on the primary or secondary (or both); which is it?

rob

[KM1H]

Thats man size iron! My big mod xfmr weighs 385# in oil and rated at 7400W. Couldnt find anything smaller in the 1000-1500W range but at least it doesnt worry about small mismatches.

I still need plastic sockets and chimneys for a 4x1

Carl

[K5UJ]

just re-read the original post--sorry I didn't get it sooner--the 0 on the primary is the "neutral" or center tap.  Let's say you have your standard single phase house service on the primary:  two 120 v. hots, one on each end of the primary winding to get you your 240 v.--you can use the 0 tap for any thing you want to power in the rig that runs on 120 v.   It might be a blower for example.  The blower's hot line connects to one of the 120 v. hots and its neutral return connects to the 0 tap (but you absolutely do not connect that 0 point to a real neutral return to your breaker panel).   

I would not draw a lot of power from one side of primary without an equal load on the other.  You are okay with something small though.   I have also heard of guys with high watt variacs but that are 120 v. jobs, using them between one hot side and 0 on a 240 v. primary to bring up a rig slowly.  Now that seems electrically unbalanced so I'm interested in reading what someone with experience in this has to say.   Perhaps I am over cautious. 

[W7TFO]

Nah, it is not wound that way.  The cutback tap is on the other side of the 'O' (common), but the winding is not symmetrical nor is it center tapped.  It is just a bit more winding on the primary to allow a lower secondary output via relay selection for 250- or 500-Watt output.

The BC-1H transmitter had no 120-Volt demand.  All transformers in it were to use 230-Volt service, with a ground only and no neutral. 

Also with that arrangement you could use it on two legs of a 208-Volt 3-phase if necessary with the provided taps.

[N8UH]

Thanks guys! Sounds like a convenient way to lower power. A relay or two, and a discreet switch on the front panel labeled "STRAP"

[K6IC]

Tim(othy),

Wow,  that Dahl Iron sure looks great and ample.

I even love the look of that floor .. very nice !

Have Fun,  Vic