[ARC5] [Milsurplus] Screen Bias in ARC-5 Transmitters

[J. Forster]

Hi,

I am looking at the simplified Modulator print in AN 16-30ARC5-2, Fig 4.2

> On 24 Oct 2013 at 17:33, J. Forster wrote:
>
>> In CW, the VR tube is switched out, so the screen voltage will be much
>> higher...  probably 450 to 500 VDC.
>
> I don't understand: do you mean in your present supply?

I have no present supply. I'm looking at how the 1625s were used in the
ARC-5 Tzs, and intend to do a test setup roughly emulating the nominal
conditions.

> There is no VR tube in the original supply, and 450 to 500 VDC screen
> voltage would be MUCH too high in every case !!!

I never sais 400-500 on the screen.

> Maximum rated screen voltage for 807/1625 is 300 VDC.
>
> What power supply are you talking about here?

I have a few DC supplies.

My intent is to set the tube up as follows:

  Cathode to GND.

  12.6 VAC or VDC on heater.

  Control Grid to function generator w/ offset

  Screen to DC supply, through roughly 1k resistor

  Plate to 500 - 550 VDC through 1k current sampling resistor; AC coupled 
DMM across current sampling resistor.


  'Scope on plate.

The function gen amplitude and offset are adjusted to give a pretty good
current swing on plate.

-John

================




>
> Ken W7EKB
>
>