[Collins] Help Needed Diagnosing a 30L1 Loading Problem

w2cqm at juno.com w2cqm at juno.com
Tue Mar 13 19:24:55 EST 2007




I recently acquired a basket case Collins 30L1 and successfully 
replaced the filter capacitor,diode and bleeder board. The result was 
a welcomed  increase in voltage to about 2Kvdc on the plate.  Added an 
antenna (12VDC) soft key for  solid state exciter compatibility. With 
everything checking out OK, I attempted to load up the amp for the 
first time.  With about 5w of drive on 80m I made 100w output but the 
antenna tune capacitor was almost completely unmeshed (minimum 
capacitance) and no resonance  dip. Plate tune dip OK! With 50w of 
drive achieved 400w output with no antenna tune (unmeshed)  load 
capacitance. Plate tune dip OK. On 40m pretty much the same results 
however on this band  the antenna tune capacitor was completely meshed 
and no dip on this control. Plate tune cap dip OK.  Output on 20m was 
very low and on that band there was no mesh (minimum capacitance) on 
the antenna tune cap. Plate tune dip OK. Didn't go any farther with 
the tests.  Admittedly, I'm not at all familiar with the 
characteristics of the Collins 30L1; consequently, I'm not quite 
certain where to begin to look for a solution. The swr between the 
exciter and amplifier was within tolerances and the exciter power 
output  was not folding back.   I was wondering if the above set of 
facts indicates that one or more than one of the 811A's is in need of 
replacement or perhaps the problem is elsewhere. Any comments would be 
appreciated. Regards, Ron W2CQM/3

PS: If you're interested in seeing the replacement filter/bleeder PC 
board accompanied with brief annotations, visit:
http://briefcase.yahoo.com/W2CQMron  and select "Collins 30L1"  




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