[Amps] Sb-200 plate current (again)

[2]

>Hi Jeff, etc.,
>
>I lost one of those resistors many years ago.  I would say old age.  Maybe
>some stray current, but I replaced the 33 ohm 1W with 33 ohm 2 Watt
>resistors.  

€  the typical grid-current in a 572B will not blow even a 1/4W 33-ohm resistor.

>One of my tubes was not working with the 33 ohm resistor blown.
>The other was bright orange, taking all the load.  You may have one tube
>either cut off or "floating along".  I do not remember if I was getting 300
>or 500 watts when this happened.  By the way, I was on 40 phone and happened
>to stand up and look down on the amp, and saw one tube bright orange and one
>black.
>
>If you are getting 500+ watts out and an indication of only 200 ma plate
>current, I would also look at the plate current resistors, R12 and R14 and
>make sure the plate meter is reading close to 500 ma.  R12 could be low or
>R14 could be high or both.
>The grid current at 500 ma plate current should be about 150 ma.  Look up
>the current data sheets by Svetlana or similar on line. My old ARRL handbook
>does not give grid current for grounded grid operation, just 500 ma max for
>a pair and 600 watts out for 1100 to 1200 watts input.
>
>Good luck,    George    K8GG
>
>
>----- Original Message -----
>From: "Jeff Stewart" <stewgoat at indy.net>
>To: "amps" <amps at contesting.com>
>Sent: Friday, June 13, 2003 9:18 PM
>Subject: [Amps] Sb-200 plate current (again)
>
>
>>      I just did a visual and a 33 ohm resister off the grid of one tube
>R21 or R22 is cracked in two.  The tube on that side has a discoloration on
>one side (the gitter appears to be at the bottom) so it may be toast.  Now
>to figure cause and effect I guess before I replace the resistor.
>Suggestions?
>>
>> Jeff
>>
>> http://www.qsl.net/ka9dad/
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>>
>
>
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Rich, AG6K, 805-386-3734, www.vcnet.com/measures