[ARC5] Army/Navy transmitters from a NON COLLECTOR viewpoint, the ham version...

[Kenneth G. Gordon]

On 10 Feb 2020 at 22:14, Rich Post wrote:

>     1: Can either variant be either screen or plate modulated?

Yes....or cathode modulated....or controlled-carrier modulated...or...

>     2: Any suggestions on how a beat-up FT-226-A tray might accommodate either style 
>     transmitter? 

Put one of each type of socket at the rear.

> I am thinking having each
>     rear connector wired for a particular transmitter pin out, but how to avoid accidentally 
>     putting the wrong version in the wrong
>     slot? One side Army, one side Navy...

You would have to have two different "sockets" mounted, one Army, one Navy. The (later) 
Navy one is a bit larger and has different pin spacing. So there wouldn't be much danger of 
plugging them in wrong.
     
>     3: For power... a modified Heathkit PS-23 junker... get rid of the voltage doubler nonsense 

What is your main dislike of the voltage-doubler? If you replace the 150 MFD caps with 
those with MUCH greater capacitance, there are several real advantages to using 
voltage-doublers. For one thing, the output voltage ramps up a bit slower, so, often, 
step-start isn't needed.

There is nothing, really, non-sensical about them. I like them.

As an old handbook I found many years ago proved, if your total filter capacitance is at least 
30 MFD, droop will only be limited by the power transformer internal resistance.

Higher values of capacitance (easy, these days) results in much better dynamic 
regulation...as proven in an old GE Ham Notes by test.

I replaced the 150 MFD caps in my Heathkit SB-200s with 560 MFD caps in one of them 
and 620 MFD caps in the other , for instance. 

In my case, the only "ARC-5" transmitters I own were, literally, hacked to ribbons long 
before I ever got them, so I am not a bit averse to doing whatever is necessary to get them 
in operation.

Also voltage-reguating the 200 volt supply for the 1626 is an excellent thing to do. And 
voltage regulating the final amp screens is, IMHO, about the best thing you could do for CW 
work. I heartily approve of Rich's suggestions.

Do remember to remove the screen voltage whenever you remove plate voltage, or the 
screens may "disappear", usually in a flash of light.

DC on the filaments, at least for the oscillator is also pretty much necessary.

Ken W7EKB