SB-201 no plate, high grid

[Jan Ditzian]

Ed, Mike (W5RKL), Ken (W7EKB),

All three of you responded to my request for help with my SB-201 that 
had high grid current and no plate current.  I thank all of you.

I replaced the burned-put grid choke coil with a 5-amp version, and the 
1.5-ohm meter shunt resistor (it was in two black pieces) for grid 
current readings.  I had earlier removed the 1.5-ohm resistor that was 
in the place where the choke should have been.  I now have the 
following: (1) grid current reading, (2) plate current reading, (3) 600 
watts out (I have not tried pushing things), and a 599 from HI8RV on CW 
(he was 579).

The bands are so dead that I have not been able to test it on SSB yet. 
There may or may not be a problem.  I see that the amp appears to 
distort unless I cut the audio gain way down, but I cannot translate 
this into power out.  I checked further and it may be a simple case of 
loading the amp to its output limit.  I tuned up with less drive from 
the Omni 6 and now I can push the audio gain (the Omni will not modulate 
above the power level set by the power control, which is the fixed power 
while tuning or running CW).  I am using one of the old, old Cetron 572B 
tubes, and one brand-new Chinese no-name 572B tube from RF Parts ($34).

The upshot is that I am back on the air with this amp, which came to me 
from St. Helena, after doing some service there.  If I feel that I still 
have a problem to resolve, I will ask it on the Heath reflector, where 
hams like you are waiting.  You three gentlemen epitomize ham radio 
spirit in terms of helping one another out.  I appreciate it, and I hope 
that you each continue for many years helping out those who do not know 
what you know about radio, or Heath radios.

May you all have good health, good luck in the new year, and good DX of 
course.

73,

Jan, KX2A

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