©1995 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 5/3/04
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CONSTRUCTION.
a. Set heatsink on bench, oriented
as in figure 1. Note where PA transis-
tor is to be mounted to two adjacent
holes. Align the pc board with the
heatsink, matching the cutout for the
transistor and the pc board mounting
holes with the holes on the heatsink.
Note that the heatsink is used for sev-
eral products; so there may be extra
holes to the left of the pc board which
are not used in this model.
b. Temporarily remove the pc
board, and lay it on a box or hold it in
a vise horizontally with the etched
side of the board up. Using a sharp
pick or any other convenient tool, pick
up eyelets and place them in the small
holes on the board. The heads of the
eyelets must rest flat against the foil
on the etched side of the board. Then,
using a small amount of solder, solder
the heads of the eyelets to the foil.
The eyelets connect the pc board front
and rear ground planes together at
critical locations. Be sure all small
holes are thus connected through. If
you lose an eyelet, bus wire can be
used.
c. Turn the pc board over, and
solder the other side of the eyelets to
the ground plane. Be sure all are sol-
dered, and check to make sure none
have slipped back through the other
side. If so, heat eyelet flange on top
side of board until solder on both
sides melts, and push eyelet gently
back in place. Note that it is espe-
cially important that the 8 eyelets un-
der the emitter leads of Q1 are
properly seated and that no solder
blobs protrude above eyelet heads.
This is to prevent stress on transistor
leads when it is later installed.
d. Set two #8 flat washers over
each of the 3 enclosure holes used to
mount the pc board (not the 2 transis-
tor holes).
The two washers provide
the proper thickness for the pc board
spacing needed for the transistor; so be
sure to use the ones supplied to pre-
vent damage to the transistor.
Set the
pc board in place, and secure with
three each 6-32 x 3/8 inch thread
cutting screws. The screws go
through the pc board and spacer
washers and thread into the alumi-
num heatsink.
Be careful not to over
tighten the screws and strip the
threads.
e.
Locate the power transistor, and
note that the collector lead is the nar-
row one (see component location dia-
gram). The collector lead should face
the right-hand side (toward connec-
tors). Apply a small amount of
heatsink compound to the bottom
surface of the transistor, and set it in
place through the cutout in the board.
f. Secure the transistor with two
4-40 x ½ inch screws inserted
through the transistor flange into the
heatsink. Use lockwashers and nuts
on the fin side of the heatsink. Align
the transistor with the board before
tightening screws.
Refer to the pc board component lo-
cation diagram in the rear of the man-
ual for the following assembly opera-
tions.
g. Solder the six transistor leads
to the pc board. It is important to
solder the entire surface of each lead
and use enough solder to form a bond
under the leads.
h. Install the metal clad mica ca-
pacitors in the exact positions shown.
The flat side with the value markings
should be up. Bend the tabs down so
they just touch the board with the
case flat against the board. Hold each
capacitor in place and solder the tab
to the board. Then, solder each side
of the metal case to the ground plane.
C3-C6 should be over the emitter
leads, as close to the body of the tran-
sistor as possible. C7 should have its
tab bent up slightly. It acts as a free-
standing terminal above the board.
Its tab does not connect to the board,
just the case.
i. Solder the mylar and disc ca-
pacitors and the electrolytic capacitor
(C9-C11) in place as shown. The
.01uF capacitor may be marked "103".
The mylar capacitor is red. Observe
polarity of electrolytic capacitor. C11
is connected from the tab of C7 to
ground.
i. Cut a brass strap 3/16 x 1
inch (approx.), and solder it down to
complete the stripline from the base of
Q1 to the hole under the position of
C2 on the diagram. (This pc board
was originally designed for another PA
which had a driver transistor which is
not used in this model.)
k. Solder the tabs of variable
mica capacitor C12 in the position
shown, between two pads on the pcb.
l. Prepare the three piston ca-
pacitors by cutting off the two narrow
lugs from the bottom of the main body
of each capacitor. Bend the narrow
lugs at the end of the rotor straps over
at a 90-degree angle away from the
capacitor.
m. Set C2 in place on the board
as shown and tack solder in place. It
will be necessary to bend the rotor
strap out away from the capacitor
body at an angle to straddle the large
hole in the board. The capacitor itself
can be installed on a slight angle, and
the strap will be at an angle. Tack
solder the lugs at the bottom of the
main body of the capacitor first and
then the rotor strap.
n. Likewise, set C1 in place and
solder to the board with the two lugs
HAMTRONICS® RPA-302 UHF REPEATER POWER AMPLIFIER
ASSEMBLY, OPERATION, & MAINTENANCE INSTRUCTIONS
Figure 1. View of Heatsink
Mounting Screws
Hole Not Used
