[Hallicrafters] HT-32A finals resting current

[Glen Zook]

The 6293 is NOT an equivalent of the 6146B/8298A.  It is basically a 6146A/8298 with a heavier plate that allows 1000-watts peak input power as a pulse modulator.  Idling plate current should be 40 mA.  You can increase the idling plate current to 50 mA if you are driving a linear amplifier.

When run at the same parameters as a 6146 or 6146A/8298, the 6293 will typically last at least 5-times as long as the 6146 or 6146A/8298.  In fact, even longer life is not unusual.
 
Glen, K9STH 

website:  http://k9sth.net


On Saturday, September 27, 2014 4:20 PM, David C. Hallam <dhallam at knology.net> wrote:
 


I would believe 50 mA is about right for the pair.  If you are really 
concerned about it, you could run a test.  Using a dummy load apply a 
two tone signal of about 4 mA rms to the microphone connector and tune 
for full output.  Look at the output on a scope while you vary the 
finals' bias.  You should be able to easily see the effect of bias 
voltage on your two tone signal.

David
KW4DH

On 9/27/2014 12:21 PM, Jeff wrote:
> Does anyone know what the resting current (standby) should be for 
> 6293s in an HT-32A?
>
> I recently put solid state rectifiers in the rig, lifting the 5V 
> filaments out (original transformer, and I'd like to keep it that 
> way.) Obviously voltages are higher throughout, but so far, no problems.
>
> I have a meter on the HV line right now, and have the bias set for 
> about 52 mA at rest (standby position), 250 mA at 100 watts carrier.  
> I increased the value of the resistor in series with the bias pot 
> (R62) to give me more control over the resting current Before doing 
> this, the lowest I could get the bias current was around 80 mA.  I'm 
> using the 50-60 mA range based upon all the rest of my hollow state 
> gear, so I'd appreciate anyone's more learned advice.
>
> Jeff
> WB3JIH
>
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