Page 4 PH I LCO
Service Bulletin No. 193
Adjusting Compensating Condensers
The compensating condensers of Model 144 have been
adjusted accurately before shipment. H later adjustment is
required, in most cases only the intermediate frequency and
low frequency compensating condensers should be done.
Extreme ca.re must be given the adjustment of the high
frequency circuits, and the adjustment should NOT be under-
taken unless the receiver is seriously out of alignment.
DO NOT ATTEMPT TO ADJUST the compensating
condensers mounted upon sections numbered 3 and 4 of the
Tuning Condenser Assembly (Fig. 5). These have been
adjusted, and sealed, at the factory.
Philco Model 024, an accurately calibrated signal genera.tor
covering broadcast and police band frequencies, is recom-
mended for the adjustment of the intermediate frequency and
low frequency compensating condensers.
Philco Model 091 crystal-controlled Signal Genera.tor is
reco=ended for the high frequency adjustments. It gives
an accurate and constant 3600 kilocycle (3.6 mega.cycle)
signal, the harmonics of which include the necessary high
frequencies for adjusting the compensating condensers in
the high frequency circuits.
!-ADJUSTMENT OF THE INTERMEDIATE
FREQUENCY-Remove the grid clip from the type 6A7
tube and connect the "ANT" output terminal of the signal
genera.tor to the grid cap of the tube. Connect the "GND"
terminal of the signal genera.tor to the "GND" terminal of
the receiver chassis.
Connect an output meter to the primary terminals of the
output transformer. Set the signal genera.torat 460 K.C. (the
intermediate frequency of Model 144) and adjust ea.chof the
I. F. compensating condensers in turn, to give maximum
response in the output of the receiver. The location ofthe I. F.
compensating condensers is shown in Figure 5. Ea.chof the I. F.
transformers has a.dual compensating condenser mounted at
its top, and accessible thru a.hole in the top of the coil shield.
In the dual compensators, the Primary circuit is adjusted by
turning the screw; the Secondary circuit is adjusted by turning
the hex-head nut.
2-ADJUSTMENT OF THE WAVE TRAP-Replace
the grid clip upon the Detector-Oscillator tube (Type 6A7).
Connect the output leads from the signal genera.tor directly to
the antenna. and ground terminals of the receiver. Set the
Wave-Band Switch of the receiver to the standard broadcast
band (extreme left) and the Station Selector at the low fre-
quency (520K.C.) end. Adjust the Wave Trap© condenser
to give MINIMUM response to a. 460 K.C. signal from the
signal genera.tor. The Wave Trap © is located at rear and
underneath the chassis, and is shown iBtFigures 4 and 5. It is
reached from the rear of the chassis.
3-ADJUSTMENT OF THE DIAL FREQUENCIES--
Model 144 has four separate frequency bands or ranges, each
obtained by one of the four positions of the wave-band switch.
There is a.compensating condenser for ea.chrange, which must
now be adjusted. In the following procedure, the frequency
rangesreferred to, and obtained by the different positions of
the switch a.re:
Range 1... ..... ..... ... 520 K.C.-1500 K.C.
Range 2.... ... ......... 1.5 M.C.-4.0 M.C.
Range 3. .. ......... .. . .4.0 M.C.-11.0 M.C.
Range 4..... .......... .11.0 M.C.-23.0 M.C.
Connect the output terminals of the Model 091 or equivalent
Signal Genera.tor, to the "ANT" and "GND" terminals of the
receiver chassis. Connect an output meter to the primary
terminals of the Output Transformer of the receiver. Set the
Wave-Band Switch to Range 4, and the Station Selector at
21.6 M.C. The sixth harmonic of the 3.6 M.C. crystal in the
Model 091 Signal Genera.toris picked up at this point. Adjust
the compensating condenser @ on Section 1 of Tuning Con-
denser for maximum response in the output of the receiver.
Turn the Wave-Band Switch to Range 3, and the Stat ion
Selector to 10.8 M.C. Here, the third harmonic of the 3.6
M.C. crystal will be heard. Adjust the compensating con-
denser @ on Section 2 of Tuning Condenser for maximum
response in the output of the receiver.
Turn the Wave-Band Switch to Range 2, and adjust the
Station Selector to 3.6 M.C. The "Antenna" connection
between the Signal Generator and the receiver chassis must be
removed for this adjustment, otherwise the output of the
Signal Genera.tor will be too great. Adjust the compensating
condenaer @ to give maximum response in the output meter.
This compensating ' condenser is located underneath the
chassis and is not accessible from above. See Figure 4.
This concludes adjustments requiring the Model 091 (or
equivalent) high frequency signal genera.tor.
The 'Model 024 or its equivalent is now used a.gain. Turn
the Wave-Band Switch of the set to Range 2 and the Station
Selector to 1.5 M.C. Set the Signal Generator at J500 K.C.
Make sure the "Antenna" connection between the Signal
Generator and the Obassis bas been restored. Adjust com-
pensatin~ condenser @ located underneath the chassis,
(Figure 4). Adjustment isma.defrom the underside ofthe chassis.
Turn the Wave-Band Switch to Range 1 and the Station
Selector to 1400 K.C. Set the Signal Generator at 1400K.C.
Adjust compensating condenser @, which is located under-
neath the chassis. (See Figure 4). This adjustment is made
from the underside of the chassis.
Finally, with Wave-Band Switch at Range 1, and Station
Selector at 520 K.C., set the Signal Generator at 520 K.C. and
adjust compensating condenser@ (Figure 4). This compen-
sating condenser is also mounted underneath .the chassis, and
reached from below.
For proper and accurate adjustment of Model 144,
the procedure must be followed exactly in the order
given. The adjustment should not be undertaken
without proper equipment as mentioned above.
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ST.-.TION WAV!.ll-'N0 ONE
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Fig. ~Position of CompensatingCondensersReachedfrom AboveChassis
USE PHILCO REPLACEMENT PARTS AND TUBES FOR EVERY MAKE RADIO. GET
COMPLETE CATALOG FROM YOUR DISTRIBUTOR
PHILCO RADIO AND TELEVISION CORPORATION
May, 1934
Printed in U. 8. A Service Department
