[Collins] Help Needed Diagnosing a 30L1 Loading Problem

[Dave, K2DP]

Ron,

I'm a bit confused by your dialog below where you refer to a "dip with the 
loading capacitor to achieve resonance"

You want to dip the plate and increase loading as you bring up the drive 
from the exciter.

Aside from the other comments on the reflector relative to the bandswitch 
being funky or mis-aligned, I would check the value of the resistors in the 
parasitic chokes on the plate caps of the 811A's and the grid resistors on 
the base of the tubes (beneath the chassis plate) Both of these resistor 
sets dissapate a lot of heat over time and get pretty crunchy looking, which 
means replace them with new old stock carbon comp resistors.

Also check the SWR of the tuned input circuits on each band by reading the 
SWR from your exciter into the amp with the amp terminated into a dummy 
load. It is possible that someone had re-aligned your amp for military or 
commercial frequencies.

The 30L-1 runs 600 watts output key down into a flat load. Anyone that 
squeezes more out of the amp is just pushing it.

73 and good luck,
Dave, K2DP, St. Louis
----- Original Message ----- 
From: <w2cqm at juno.com>
To: <Collins at mailman.qth.net>
Cc: <W2CQM at juno.com>
Sent: Tuesday, March 13, 2007 7:24 PM
Subject: [Collins] Help Needed Diagnosing a 30L1 Loading Problem





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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