[Johnson] Viking Thunderbolt

[Steve H]

Yes, I have read thats the band hams usually pick.

I did try what someone else sugguested, a "cold neutralize",
where you feed some low level drive into the output jack
of the amp, and scope the input jack for signal.

Optimize for highest reading with the main plate tuning
deck and in this case the grid control knob.

I tried it with no power to the amp and saw a small signal
I neutralized on the input connector with the scope, but 
you are suppose to do it with the heaters on for the tubes.

Seems to have mostly worked, though the tubes still seem 
a bit unbalanced where one is glowing redder than the other,
therefore doing more of the work, so with one tube there
was about 600W, now after the adjusting, there is about 775
or so on the 20m band that was just set.

I have a hunch for it to be optimized you need to neutralize 
on the specific band you are on.

When I set the cap for 80m and both tubes lit the same level,
I had 1100W and the cap was about 90% max capacitance.
As I left that band, I have reduced capacitance greatly so I guess
if I were to recheck on 80m, I would have reduced power there
like I saw when I started.


--
Steve Hearns [ KA2PTE ]



----- Original Message ----- 
From: <manualman at juno.com>
To: <johnson at mailman.qth.net>
Sent: Monday, May 22, 2023 10:15 PM
Subject: Re: [Johnson] Viking Thunderbolt


> Neutralization generally is most critical on 10 meters so whenever I have
> to do a neutralization adjustment, I always do it on that band.
> 
> Pete, wa2cwa
> 
> On Mon, 22 May 2023 12:31:33 -0500 <garyschafer at largeriver.net> writes:
>> Hi Steve,
>> I do not own a thunderbolt. but to neutralize you want to watch the 
>> grid
>> current as you tune the plate tune cap.
>> You should see a peak in grid current at the same time you see the 
>> plate
>> current dip.
>> You may have a more sensitive reading if you do not load the plate 
>> to full
>> output when neutralizing. 
>> 
>> If you watch which side of the plate dip causes the grid current to 
>> go down
>> you can determine which way to go with the neutralizing cap. When 
>> you see
>> the grid current go up when moving the plate in the same direction, 
>> that
>> means that the neutralizing cap needs to go the other way.
>> This should be done on 20 meters for balance on all bands.
>> 
>> 73
>> Gary  K4FMX
> 
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