[ARC5] Operation of ARC-5 Transmitter

[Kenneth G. Gordon]

On 15 May 2016 at 8:40, Cliff Miller wrote:

> 
> Thanks everyone for the replies.  I checked for the screen grid mods but found the transmitter to 
> be stock with no SG connections except the rear connector.  I had 239V on the oscillator power 
> input and got no glow on the 1629.

Do you mean no "green" display at all? If so, that sounds as though no HV is getting to the 
circuit at all. Have you checked the can-cap mounted in the rear? It could be shorted.

>  All the filaments are lit FB but no joy.

What do you mean by that? The oscillator was not working?
   
> Any checks I could do before ordering a new magic eye tube?

The only thing the magic-eye tube does is indicate when the dial is correcty tuned to the 
crystal frequency. Otherwise, it is pretty much useless and the only thing it does is to "soak 
up" 12.6 V of the 25.2 V input to balance the 1626's filament voltage. Knowing the ARC 
engineers, I suspect they also used the heat from the 1629 to keep the VFO more stable.

>  Is the difference with 250V 
> enough to prevent proper operation?

No, if you mean would this prevent the oscillator from operating. "Best" voltage for the 
oscillator plate is 200 VDC or very close in order to minimize chirp and drift, but anything a 
bit higher or lower is not going to prevent it from operation.

Ken W7EKB