Page 4 PH I LCO
Service Bulletin No. 188
ADJUSTING MODEL 34 ·
The compensating condensers of Model 34 have been
adjusted accurately before shipment. If later adjustment
is required, in most cases only the intermediate frequency
and low frequency compensating condensers should be
done. Extreme care must be given the adjustment of the
high frequency circuits, and the adjustment should NOT
be undertaken 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. These have been
adjusted , and sealed, at the factory.
Philco Model 048 All-Purpose Set Tester, which incor-
porat.es a signal generator covering broadcast and police
band frequencies, is recommended for the adjustment of
the intermediate frequency and low frequency com-
pensating condensers.
Philco Model 091 crystal-controlled Signal Generator is
recommended 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.
I-ADJUSTMENT OF THE INTERMEDIATE
FREQUENCY-Remove the_grid clip from the type 1C6
tube and connect the "ANT" output terminal of the
signal /fenerator to the grid cap of the tube. Connect the
"GND' terminal of the signal generator to the "GND"
terminal of the receiver chassis.
Connect the output meter to the primary terminals of
the output transformer. Set the signal generator at
460 KC. (the intermediate frequency of Model 34) and
adjust each of the I.F. compensating condensers in turn ,
to give maximum response in the output of the receiver. ·
The location of the I.F. compensating condensers is shown
in Figure 2. Each of these transformers has a dual com-
pensating condenser mounted at its top, and accessible
thru a hole in the top of the coil shield. In the dual com-
pensators, 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 1C6).
Connect the output leads from the signal generator
directly to the . antenna and . ground . terminals of the
receiver. Set th\! Wave-Band Switch of the receiver to the
standard broadcast band (Range 1) and the Station
Selector at the low frequency (520 KC .) end. Adjust the
Wave Tr~p q) condenser to give MINIMUM response to
a 460 KC. signal from the signal generator. The Wave
Trap © is located at rear and underneath the chassis, and
is shown in Figures 2 and 5. It is reached from the rear
of the chassis.
3-ADJUSTMENT OF THE DIAL FREQUENCIES
_;_Model34 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 each
range, which must now be adjusted. In the following
procedure, the frequency ranges referred to, and obtained
by the different positions of the switch are:
Range 1. ... . . .... . .520 KC .-1500 KC.
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 Generator, to the "ANT" and "GND"
terminals of the receiver chassis. Connect an output
meter to the primary terminals of the Output Trans-
former 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
Generator is picked up at this point. Adjust the com-
pensating condenser @ on ~ection 1 of Tuning Condenser
for maximum response in the output of the receiver.
Turn the Wave-Band Switch to Range 3, and the
Station Selector to 10.8 M.C. Here, the third harmonic
of the 3.6 M.C. crystal will he heard. Adjust the com-
pensating condenser @ 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" connec-
tion between the Signal Generator and the receiver chassis
must be removed for this adjustment , otherwise the output
of the Signal Generator will be too great. Adjust the
compensating condenser @ to give maximum re.'lponsein
the output circuit. This compensating condenser is
located underneath the chassis and is not acces.'liblefrom
above. See Figure 5.
This concludes adjustments requiring the Model 091
(or equivalent) high frequency signal generator.
The Model 048 or its equivalent is now used again.
Tum the Wave-Band Switch of the set to Range 2 and the
Station Seleetor to 1.5 M.C. Set the Signal Generator .at
1500 K.C. Make sure the "Antenna " connection between
··the Signal Generator and the Chassis has been restored.
A_djust compensating condenser @ locat~ underneath the
chassis, (Figure 5). Adjustment is made from the under-
si!-Jeof the chassis. ·
;'Tune the Wave-Band Switch to Range 1and the Station
Selector to 1400 K.C. Set the Signal Generator at 1400
K-.C. Adjust compensatin_gcondenser @, which is located
underneath the chassis. (See Figure 5). This adjustment
is made from the underside of chassis.
Finally, with Wave-Band Switch at Range 1,and Station
Selector at 520 K.C., set the Signal Generator at 520 KC.
and adjust compensating condenser @ (Figure 5). This
compensating condenser is also mounted underneath the
cha11Sis,and reached from below.
For proper and accurate adjustment of Model 34,
the procedure must be followed exactly In the order
given. The adjustment should not be undertaken
without proper equipment as mentioned above.
USE PHILCO REPLACEMENT PARTS AND TUBES FOR EVERY MAKE RADIO. GJT
COMPLETE CATALOG FROM YOUR DISTRIB UTOR.
PHILCO RADIO AND TELEVISION CORPORATION
Maroh,1934
J'rinted in U. S. A. Service Department
