[AMPS] Grid current "drift"

[km1h@juno.com]

On Sat, 17 Oct 1998 22:32:40 EDT KA2YKC@aol.com writes:
>
>Good Evening.
>
>
>I have been noticing on my 2x3CX800 amp that if I tune up for legal 
>limit, I
>get the following readings which are within spec - Ip=1000ma, 
>Vp=2000v,
>Ig=40ma.


40ma seems a bit high altho well within Eimac spec for 2 tubes.  I
usually ran my LK-780 2 holer at about 20-30ma when RF out peaked.


>
>However, if I unkey, wait a few seconds, then rekey, my Ig is up 
>around 60ma
>or more. As I hold the key down, the Ig will slowly drift back to 40ma 
>or so. 

SNIPPED

>
>Same results with 2 set of tubes, also the RF ouput seems to stay 
>stable on
>the Bird 43 while the current drifts downward when testing this in CW 
>mode.
>Happens on 20, 17, and 10m.
>
>BTW, the antenna system checks good (very low swr, no change on Bird 
>while the
>grid drifts). Is this normal (I wouldn't think so) ? 
>
>Is is possible that there is some heating taking place in the output 
>network ?


Input OR output.
If the input components are undersized you may get similar results
depending upon how they are tuned.
Undersized,  defective or improperly soldered components anywhere in the
outpath from the plate blocking cap to the antenna connector are
culprits.
Look for unexpected or excessive heat...after the HV is bled off !!

73  Carl  KM1H
>
>
>TIA for your comments..........
>
>73
>Eric
>
>
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