Heathkit HW-12 - Page 50

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bridge to make sure it has an SWR of 1-1/2 to
1, or less, Operation with a high SWR will re-
sult in overloading the output tubes, When using
a SWR bridge, carrier may be obtained for tuning
the antenna by switching the FUNCTION switch
to the TUNE position. Care must be taken that
the SWR bridge is not overloaded when trans-
mitting SSB, since the peak output power is
much higher than the output in TUNE. The an-
tenna must be matched to, and fed with, 50 2
coax cable for best results; the transmitter is
not designed to load into random lengths of
wire or open-wire transmission lines,
Special care must be taken with mobile installa-
tions, since short loaded and center loaded an-
IN CASE OF
1, Recheck the wiring, Trace each lead in
eolored wneneil om the Diaetorial as it ia
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checked, It is frequently helpful to have a
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familiar with the unit may notice something
consistently overlooked by the constructor
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kits that are returned for repair, do not
function properly due to poor connections
and soldering, Therefore, many troubles
can be eliminated by reheating all connec-
tions to make sure that they are soldered
as described in the Proper Soldering Tech-
niques section of this manual.
3. Check tobe sure that all tubes andcable con-
nections are in their proper locations. Make
sure that all tubes light up properly.
4, Check the tubes with a tube tester or by
substitution of tubes of the same typ és
and known to be good,
5. Check the values of the parts, Be sure
that the proper part has been wired into
the circuit, as shown in the pictorial
diagrams and as called out in the wiring
instructions,
tennas are very critical to tune. An operating
frequency change of 10 or 20 ke will often change
the antenna tuning considerably. Better antennas
with loading coils have higher "Q'' and sharper
tuning, Follow the antenna manufacturer's in-
structions carefully to obtain proper adjustment.
Convenient, accurate signals at 100 ke inter-
vals for receiver dial checking can be obtained
by using the Heath Crystal Calibrator, The
Crystal Calibrator can be plugged into the
calibrator socket of the Transceiver. It is
turned on by pulling out the AF GAIN control
knob.
F DIFFICULTY
=
Check for bits of solder, wire ends or other
foroaion attor which mary he lodead in the
forcign matter Wnicnhn May ve .zoGgea in tne
wiring,
7. If, after careful checks, the trouble is still
not located and a poltinoter is available
not located and a voltmeter is available,
check voltage readings against those shown
in Figures 11 and 12, NOTE: All volt-
age readings were taken with an 11 meg-
ohm input vacuum tube voltmeter, Volt-
ages may vary as much as 10%.
8, A review of the Circuit Descriptions will
prove helpful in indicating where to look
for trouble,
9, Check the power supply and antenna,
NOTE: To aid in servicing or troubleshooting
the Transceiver, refer to the Resistance and
Voltage readings on Figures 11 through 13 and
the Circuit Board X-Ray Views shown in Figures
14 and 15 on Pages 54 and 55.
Breaks in the foil of the circuit board can
easily be detected by placing a bright light
under the foil side of the board and looking
through the board from the lettered side, A
break will appear as a hair-line crack in the
foil,