[Amps] Starting up a NEW Henry amp

[Alek Petkovic]

No. I'm talking about amps like an AL-80B, in which I had to fit a new 
OEM input board, a couple of TL-922s and a FL-2100B, which had 
previously received the golden screwdriver treatment by persons unknown.

In all cases, using the Nano VNA did not give the desired result.

The TL-922 service manual specifically tells you to do the tuning with a 
good amount of drive applied.

However, in my home brew GS35B 6m amp and my Drake L75 6m conversion, 
when I substituted a resistor in place of the tube, I was able to get 
very compfortably close with the input tuning using the VNA.

John, VK6JX, also used the VNA on his home brew GS35B 2m amp and it 
worked quite well. In all of those cases, the input was tweaked with 
full drive power to reach the final setting.

Cheers, Alek.

On 14/12/2023 1:08 pm, Adrian wrote:
> Alek, Did you try increasing Q of the input to ~c 2 to produce a 
> better flywheel effect,
>
> which becomes a more stable input impedance  through a wider drive 
> level range ?
>
> More capacitance, less inductance on the input.
>
>
> 73
>
>
> vk4tux
>
> On 13/12/23 20:14, amps-request at contesting.com wrote:
>
> For what it's worth, I have had terrible problems getting the input
> matching right on several amplifiers using the VNA, yet when using
> normal drive levels, as reccommended in the user/service manuals, tuning
> is a breeze. Therefore, I think that there is some truth in the
> assertion that tuning at low levels does not work properly.
>
> 73, Alek VK6APK
>
>
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