Mike -
Your instincts are correct! :-) A T-4XC with NEW PA tubes will put out about 140W Maximum on 80 and
40M. Drops to about 130W on 20M, 125W on 15M and about 110 on 10M. Typical overall efficiency is
about 50 - 55%. The plate current will go a little over 400 mA, with a couple of caveats. First, the
meter shunt resistor tends to increase in value over time, causing the PLATE meter to read high. The
meter isn't all that accurate to begin with, being in the $1 class when new... :-) I recommend
checking the meter shunt, and then comparing it's E/R current at the IDLE current (0.07A) with the
meter. If off slightly, select a new meter cal resistor to correct it at IDLE current. This the the
most critical current, while the plate current at max is not.
Your 75W in TUNE indicates either a weak set of PA tube(s), misalignment, or low power supply
voltages. The Heathkit shop kit is an ideal upgrade and I highly recommend it. At the very least, it
is imperative that you check the BIAS supply and at a minimum replace the filter caps for this (and
other) sections of the supply. ALL caps are at least 30 years beyond their expected lifetime!
<http://www.theheathkitshop.com/>
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Michael & Sue Trussell wrote:
I just unboxed my old C line that I have had in storage for a long time. Both
units the
transmitter and receiver worked when I turned them on. The receiver to my
surprise seems to be
more sensitive and selective than my TR7 that I have been using. To those of
you who have had more
experience with these units than me, I would like to ask a few general
questions. The output of
the transmitter appears to be low, when I sent the units back to RL Drake back
in the late 80’s
for general maintenance the comments on the transmitter, RL Drake noted the
output was 180 watts
in the tune position. This seems really high! The transmitter as far as I can
remember is only 240
or 200 watts input PEP? They also claimed in the tune position to get 400
milliamps read on the
meter? Any comments or suggestions from the experienced operators what I get
now is about 75 watts
in the tune position, with 300 milliamps on 40 meters in a RL Drake dummy load.
The bias appears
to be set right according to the instructions in the manual. I would suspect
very much that the
AC4 power supply needs to be rebuilt, as far as I know it is still original
Any comments or suggestions from you would be appreciated!
I would like to know how to contact the Heathkit shop for the rebuild kits.
Unless other suggestions!
Thank you in advance
Mike KA8ASN
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