Here is a problem that I need help to solve!! Any comments from experience
would be appreciated, comments pointing out things I have not thought of
especially!!!
I am on St kitts for the cqww160ssb and the arrl dx tests, cw/ssb.
Yesterday, at 2pm with 6 hrs to go I noted that the third 3500z tube in the
LK550 was not lit thus explaing why I have been getting only 1000-1200
watt max with the amp. I had attributed this to low voltage and have since
brought the ac voltage up with a 220v variac from 195v to 220-230v measured.
For whatever reason (poor in retrospect) I shut down opened the amp and
melted the solder at the filament pins and replaced the tube. B4
this the peak power out was about 600w (10Meters) on Vectronics double
needle meter with swr about 1.4 all indicated. AFTER I operated on the
tube, which did not lite up, the pk pwr was 3-400w with no following with
keying on Ip,Ig or power needles, all just hung up AND the plates of the 2
tubes became cherry red in 4 sec of keying. I tried a dummy load with same
effect. So I shut down and pulled out and used an MLA2500 for remainder of
test.
This am I tackled the problem again. Results: All bands 160-15 showed
unchanged operation (using same tuning chart as before ie plate and load
positions on amp with same antennas etc) with same power out and stable with
keying! ON 10 METERS: Power out 300-400
watts with very slugglish and broad tuning point on plate es load knobs,
keying ok on Ip,Ig es power out but a little slow but in normal range! I
pulled the plate connector off the dead tube. Same results.
What is going on??? Now before r. Measures shoots me with a direct
minute man missle, first thought was parasitics!! BUT I went back and
checked the tank coil and all connections in plate compartment, all looked
ok. I am at loss to explain. comments help!!
Anything else??
I have shipped new 3500z and suppressor kit from home to be here in the am.
Will let you know follow-up.
I hope I have not bored you with this note, and read the messages on this
reflector with interest. Alex v47kp/w2ox
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