[Amps] 2x 4cx1500b amp

[Carl]

Why do you want the old style center tap transformer? This doubles the 
winding resistance when used in a full wave circuit.

I have had a custom transformer built with the idea it will never be 
obsolete and also allow use with several amps with different requirements.

Built for a 240V primary with multiple taps. The secondary is a single 
winding with 4 taps that allows me to select a no load DC (at a nominal 
240VAC on the 240V tap) of 2500, 3000, 3500, and 4000V in a full wave bridge 
or twice that in a doubler. Adding taps is cheap, the added insulation for 
doubler service added a bit more cost. I paid extra for the highest 
temperature wire insulation but the as built ratings are for the 
conventional insulation ratings. Its rated at 5kva so it is not light.

This PS has been in use for about 20 years and used for a pair of 4CX250B's 
to a pair of 4-1000A and everything in between.

I sold about 65 of these transformers while a local transformer company was 
still in business.

Carl
KM1H


----- Original Message ----- 
From: <texasrf at aol.com>
To: <felipe at dxwatch.com>; <Amps at contesting.com>
Sent: Monday, November 30, 2009 10:34 AM
Subject: Re: [Amps] 2x 4cx1500b amp


> Felipe, you can change hv as you described. The results will depend on how
> you intend to use the lower voltage. If your plan is to lower the voltage
> AND  plate current together to run less rf power, there will be no 
> problems.
> In fact,  you will not even need to retune the amplifier if you do that.
>
> The primary should be designed for the higher plate voltage and then have
> turns added to lower the plate voltage. Because of the added turns, the
> primary  loss resistance will be higher. The added loss resistance will 
> cause
> the no load  to full load voltage drop to be worse when lower voltage is
> selected. If the  current is also reduced, the voltage drop increase will 
> be
> lower and probably  not even noticed.
>
> I have a Peter Dahl plate transformer built this way and it has served 
> very
> well for nearly 30 years.
>
> 73,
> Gerald K5GW
>
>
>
> In a message dated 11/30/2009 7:57:43 A.M. Central Standard Time,
> felipeceglia2 at gmail.com writes:
>
> Hello  "Ampers",
>
> I am willing to build a 2x 4CX1500B amp for 160 to 10m usage.  Willing to
> use a GM3SEK tetrode board for controlling and protecting  it.
>
> As I will need to special order the HV supply transformer, I am  thinking
> about asking for a multiple voltage primary and a fixed voltage
> secondary (probably 1250v - 0v - 1250v), so it will be easier to change
> output voltage just changing the primary, instead of dealing with HV. Is
> it a bad idea?
>
> I would like to hear from you if you have built  anything like it, or if
> you have something to say.
>
> Also, are there  alternatives to the tetrode board?
>
> 73,
>
> Felipe -  PY1NB
>
>
>
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