Suspect bandswitch problems in the tank circuit sections.
Make sure the sections are INDEXED correctly. If you took the switch rod
out during cleaning or rebuilding there could be a possibility the loading
section was mis-indexed 180 degrees in one section. Its been a long time
since I have had to service a 30L-1 (not quite 30 years)
There could also be a potential problem with the switch just flat being
tarnished. Here's where gentle treatment with tarn-x and a Q-Tip and
multiple switchings could fix it. Then follow up with ALKY and a Q-TIP to
clean off the Tarn-X as you cant wash the assembled amp in water.
Do not leave chunks of cotton from the Q-Tip stuck in the switch and be very
careful not to bend contacts. I have brought many a Collins bandswitch back
from the grave.
I would NOT SUSPECT THE TUBES.
Also by tuning the loading where it is going, you could possibly be actually
pushing the amp plate into running as a doubler.
Lets make sure the bandswitch is 100% first.
BOB DD
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of w2cqm@juno.com
Sent: Tuesday, March 13, 2007 7:35 PM
To: amps@contesting.com
Subject: [Amps] Need Help Diagnosing a Collins 30L1 Amp 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 10w 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 the replacement filter/bleeder PC
board accompanied with brief annotations, visit:
http://briefcase.yahoo.com/W2CQMron and select "Collins 30L1"
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