Centruy 21..transistors


From: JEFF M. GOLD (JMG@tntech.edu)
Date: Wed Feb 02 1994 - 10:33:25 EST


Recently purchased a Century 21 off the net for my future Ten Tec

* anyone know anything about "power mites"?

I had to replace one of the finals.. RF parts had the MRF475 for 9.95. I
cross referenced it to a 2SC1969..same as used in the Gary Breeds. The
2sc1969s were $2.65.. so bought 5 or them.. figured could always use
them if I blew one in my GB. Well I had heard that the 21s put out 50
watts. I am looking at the spec.. says.."Final RF pwr Output.. 13W"

They were cheap enought so i replaced both.. figured more likely to be
closer matched. (matched sets of MRF475s were like $25.

I really liked the module design of the Century 21.. while I was in the
radio.. replaced some wires that didn't look great.... it was fun.
Wasn't real hard to replace the transistors. I think that someone hadn't
set the current limiter correctly and that is why the transistor blew.
Haven't really looked at it.. but the manual says the finals are suppose
to be protected.

The manual also said 25-30 watts. Well couldn't find anything in the
book to help me set the two thumb wheel Pots? one I know sets the meter
adjust ... the other..current limiter? Played around with them till it
seemed about right.. (not really good way.. but works sometimes).
Adjusted the power input by checking my Watt meter and noticing at which
point the radio was near full power.. coincided with about the right
power input level.. so left it alone. The rig seems to loaf at 35-40
watts on 20 meters.

I got on 80 meters and tuned my 10-12-15-17-20 meter quad for 80
meters.. pointed north (the rotor is frozen with our very cold wx) and
of course heard a station calling CQ from Guatemala. Now I lost a few
other people calling CQ.. not use to the DC receiver.. think they are
calling at one freq., I am answering at another.. played with my 850S
and adjusted the RIT on the 21 till I seemed to figure out where I
needed to be. Answered the CQ and the guy came right back to me... got a
good report also. The wattmeter was peaking at about 50 watts and
running average over 40.

Those $2.65 2SC1969s seem to be enjoying themselves and I didn't have
the power input up to the suggested level.. going to start going down to
QRP now that I know the rig works.


Jeff, AC4HF

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