©2012 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 12/22/11
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OPERATION.
Operation is quite simple. B+ can be ap-
plied all the time if desired. Merely apply an
rf signal to the PA when you want to transmit.
Being class C, the pa only draws current when
driven.
TROUBLESHOOTING.
Since the unit has only one simple amplifier
stage, there isn't much which can go wrong.
The circuitry is straightforward. The first
things to suspect should there be no output
are shorted coax cables or incorrect or
shorted pc board component connections.
Should it be necessary to replace rf power
transistor Q1, be sure to use an exact re-
placement. There are other transistors rated
at similar output level, but they may have
lower gain or different impedance character-
istics.
To replace the transistor, carefully peel
each lead away from the pc board while melt-
ing the solder. Then, remove the mounting
hardware and gently push the old transistor
out of the heatsink. Clean all the old solder
off the pc board and remove the old heatsink
compound. Add new heatsink compound,
and install new transistor with collector lead
in correct location. Carefully tighten nut on
transistor without over-torquing. Then, flat-
ten leads against the board, and sweat solder
them to the board. Remember to resolder
any components removed for access to the
transistor leads.
PARTS LIST.
Note: Some design changes have been
made since the diagrams were made. Text
and parts list take preference
.
Ref Desig
Description
C1
20pf disc
C2
30 pf (grn) ceramic var.
C3
100pf disc capacitor
C4
mica variable (C4203/08)
C5-C7
not used
C8
11pf piston trimmer
C9
mica variable (C4203/08)
C10
.001 uf + 100pf chip caps
C11
0.1 uf chip capacitor
C12
47 uf electrolytic cap
C13-C14
33 pf disc capacitor
C15
not used
L1, L3-L5
wind per text
L2
0.22 uh rf choke marked
red-red-silver-red
Q1
M25C18
R1
3.3
Ω
, ¼W resistor
R2
10
Ω
, ¼W resistor
R3
not used
Z1-Z2
ferrite bead