[Amps] Alpha 76A drive levels...

[Martin Sole]

Hi,

Is that with the HT switch in the CW or SSB position?. If the CW 
position it sounds about right. If in the SSB position and HV, Ip and Ig 
all look normal then I can only assume he has an amp without the low 
drive mod. Google Alpha low drive mod and I'm sure you will be rewarded.

Also do the math. Two 8874's, that's two tubes each with 400 watts of 
anode dissipation at max as per the specs. So 800 watts dissipation 
total. If the amp is 60% efficient then that 800 watts is the 40% left 
over as heat from the total P-in. 1200 watts out should be the maximum. 
Unless, a) efficiency is more than 60%, b) the tubes are not 8874, 
rather 3CX800.

Remember also that these are amps designed for key down US legal limit 
when US legal limit was NOT 1500 watts out!


Martin, HS0ZED.



On 24/12/2018 05:06, Gary Smith wrote:
> To the group:
>
> Have a friend who recently purchased a Alpha 76a two-holer.
>
> He currently is driving it about 65 watts getting 500 watts or so output.
>
> As he has no instructions on the amp, is this low level of drive okay 
> or should it be driven at a higher level of input power.
>
> Thanks to the group,
>
> Gary...wa6fgi
>
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