>
>I am almost embarassed to ask this. However, since my ego is inversely
>proportional to my waistline.........I have recently acquired a superb HB
>amp covering 160 to 10. Uses Dahl components in the PS, vac. variables in RF
>deck. built professionally by a EE (now SK, RIP). The tube is a single
>4cx1500.
An A or a B? The difference is great.
> My questions is how the heck do you tune this up?
1. Switch the anode and screen supplies off. With a watt of drive
applied, the grid roller inductor (if the amplifier is neutralized) is
adjusted for best swr.
2. Apply max. drive and adjust the bias V until grid current is nearly
zero. Do not readjust the grid bias V to set idling current. Remove
drive.
3. Apply anode and screen potentials.
4. Set the idling current (Zero Signal Anode Current / ZSAC) to the
recommended value with the screen V adjust.
5.. Apply max drive and tune/load the tank until the recommended screen
current is reached when the output peaks with C-tune. If the screen
current is too high, increase loading and repeak. note - If you are
tuning up with high-speed dits, multiply screen current indication by
roughly 2x.
>I have used
>triodes all of my life sans my TS-820/830 which use beam power pentodes in
>the final (2X 6146) but I just tune for max power on these. I have always
>avoided tetrodes mosly due to my ignorance of the tune up procedure.
>
With a large tetrode, a tuning chart is useful. This will speed tuneup
on often used frequencies. .
>The amp has metering for screen I and E and also grid I and E as well as
>plate I and E. What is the value I need to watch?
No grid current. No more than max allowable screen current.
>I assume that it is not
>safe to tune it like my 3-500zs which is usually just tuning for max power
>out with a string of dits at 60 wpm?
>
Tetrodes are different than triodes. To adjust the tank of a tetrode
amp. one does not need an RF output indicator. It's all done with the
screen current meter.
cheers, Lane..
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