[Elecraft] XV50 PA Bias

[Don Wilhelm]

Dave,

R39 for the XV50 should be a 1k pot.  Typo or incorrect component?
The bias voltage is not the important factor, important is the ability 
to produce the proper idling current - that is why the instructions tell 
you to measure the voltage between TP3 and TP4 when setting the bias.
The voltage at the bias pin will typically be in the 4.7 volt range, but 
there is no problem if it is higher or lower.

73,
Don W3FPR

On 10/24/2014 8:49 AM, Dave Sergeant wrote:
> R39 is correct (10k pot) as is R10 (100k) and all the measurements
> confirm this. The adjustment range, measured at pin 2 of the amplifier
> module, is 2.5-4.7V, also what is expected from the circuit. The
> maximum voltage is limited to 4.7V because of the 5mA flowing through
> R28 which swamps the 1mA bias current.
>
> What I would like to know is what the bias voltage should be on a
> correctly set up XV50. The datasheet seems to indicate it must be at
> least greater than 4.5V. It seems my amp needs more than 4.7V to get
> the correct bias, and judging from previous posts on this subject I
> don't think I am alone.
>
>