[Amps] New settings on Alpha 77SX

[Gary Smith]

Here's a new bit that happened last night.

I was on 160 and discovered the grid 
became excessive as I was transmitting, I 
had to back the loading cap back down to 
keep it WNL and the power was dropping 
proportionally to the increase of grid 
current.

When I stopped transmitting and let the 
tubes cool for 30 or so seconds, the power 
came back to normal. Transmit again and 
shortly after, the grid current rose and 
power output fell. SWR always remains 
constant.

Before I open the amp up, any suggestions 
what I might look at? I'm thinking the 
caps have failed and with Tx, there's heat 
in the the caps & the values change and 
show the issue. Maybe I need to replace 
the 160 padding caps? It shows this on no 
other band.

73,

Gary
KA1J

> Here's a curiosity I'd be interested in 
> getting input on.
> 
> The 77SX seems to be easier to tune using 
> the "B" setting, rather than the A.
> 
> It used to be easier to tune on 160M using 
> the A position on the band switch but now 
> I find in the "A" position,  I have to 
> rotate the loading cap maximally to the 
> zero position for tuning and it seems to 
> dead end out in the A position. I now have 
> to use the "B" position to tune it, and it 
> now comes close to bottoming out at zero, 
> whereas it never used to have any 
> requirement to go to the "B" position.
> 
> I'm thinking the padding doorknobs for 
> 160M have softened over the years.
> 
> Idears?
> 
> 73,
> 
> Gary
> KA1J 
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