[ARC5] T-19 Update

[Kenneth G. Gordon]

On 20 Dec 2012 at 9:58, Ian Wilson wrote:

> Looking at what is working here and what isn't:

Ha! One of the first principles of trouble-shooting! Good on ya, Ian.

>   - the 1625's draw plate current. So the filaments are lit, their
>   cathodes have a path to ground, and they have HV on the plates
> 
>   - the 1625's have screen voltage (confirmed by the magnitude of the
> screen current)
> 
>   - the 1625's have drive (negative voltage measured, so grid current
>   is flowing)
> 
>   - the plate current is much higher than if the tubes were loaded
>   correctly  - the measured output is very low
> 
> I think this indicates that everything is correct up to the output
> side of the 1625's (assuming that the oscillator frequency is OK).

He has checked that, and it appears to be OK.

> Possible problems:
>   - antenna relay not energized (or relay not bypassed)
> 
>   - padder capacitor grossly mistuned (variable through the hole in
>   the chassis side)

I don't know that you CAN so grossly mistune that thing that you get NO 
output...
 
>   - output shorted or open in the connection between the TX and the
>   load
> 
>   - broken connection between the output tank/transformer and the
>   loading coil, or broken connection in the loading coil hardware

SOMETHING so grossly mistuned that there is no way to get the plate circuit 
into resonance...i.e., anywhere NEAR a dip.

> To protect the tubes while you are debugging this, you could
> temporarily add a resistor from the screen supply to ground to act as
> a potential divider.

Or remove screen voltage completely. The 1625 will still output a watt or two 
with zero screen voltage. At least, he should still be able to find a dip.

> Hope this is helpful.

Ya done good, Ian. :-)

Ken W7EKB