[ARC5] T-19 Update

[Geoff]

GDO the output or use the diode position and check the frequency.

If nothing available use a radio to scan for the fundamental and harmonics 
and anything in between. Attenuate the RX input and hold a wire above the 
coil. Anything funny such as a parasitic or neutralization oscillation will 
be very raspy with the RX BFO on.

 A neon bulb should show RF on the antenna terminal if anything is getting 
that far.


----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "Ian Wilson" <ianmwilson73 at gmail.com>; "arc5" <arc5 at mailman.qth.net>
Sent: Thursday, December 20, 2012 5:02 PM
Subject: Re: [ARC5] T-19 Update


> 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
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