INT.FREQ.465KC.

WESTINGHOUSE RADIO MODELS WR 204 AND WR304
Seven - Tube, Superheterodyne Receiver
SERVICE NOTES
ELECTRICAL SPECIFICATIONS

GENERAL DESCRIPTION
This model is seven -tube, three. And superheterodyne receiver designed for world wide reception and employs the new all-metal tubes.

This circuit employs a high frequency amplifier using the new type 6K7 tube. This is followed by a combined first detector-oscillator circuit employing a 6A8 tube. These tubes with their associated circuits, (coils, variable condensers, trim condensers for R.F. and detector stages, and trim and lag condensers for the oscillators) comprise a complete assembly in compact form separately cushioned from the main chassis. This assembly is known as the "Precision Tuner". From the high frequency assembly the energy passes thru an I.F. selective transformer and to an I.F. amplifier tube (type 6K7). From here further selection takes place and the energy is sent to the diode (type 6H6) where second detection takes place and voltages are provided for automatic volume control. A first audio amplifier tube (type 6F5) follows the diode and this is further followed by a pentode power amplifier tube (type 6F6). A type 80 rectifier supplies the direct current for energizing the tubes.

REMOVING INDIVIDUAL COIL AND SWITCH SECTIONS OF PRECISION TUNER
If a component part located underneath the switch and coil assemblies of the "Precision Tuner" has to be replaced or a section of the unit has to be removed for inspection, each section can easily be removed separately. To do this proceed with care as follows:
1. Remove the three coil shields.
2. Remove the two self-tapping screws which fastens the mounting plane of the wave-change switch shaft to the chassis. Pull switch shaft out straight.
3. Unsolder the stator and rotor leads from the gang condenser.
4. The fastening screws for the switch sections are located on top of the "Precision Tuner" and are indicated by X, Y, and Z in figure #3. Remove the corresponding screw.
5. Each individual section can then be pulled out straight. Note: On the R.F. section, the plate lead from the 6K7 socket will have to be unsoldered from the socket before the section can be removed. On the oscillator section, the blue lead from the 6A8 detector-oscillator socket will have to be unsoldered at the switch terminal.
6. After repairs have been made resolder the leads mentioned above and replace the section being careful to observe that the slotted holes in the switch bracket line up with the round guide pins on the baseplate of the "Precision Tuner". This is IMPORTANT as the switch shaft cannot be inserted if the switch brackets do not line up.
7. Replace the section fastening screw.
8. Resolder the stator and rotor leads on the main condenser.
9. Replace the switch shaft and the mounting plate fastening screws. When inserting the switch shaft, be careful that all the switch discs are in the same positions. Otherwise the switch shaft will not slide in. NEVER force the shaft onto the switch posts. If shaft does not slide in freely, examine the position of the slots in each switch disc.
10. Before replacing the coil shields, it might be advisable to bend the shields slightly to assure that positive contact is made. To do this hold the shield with your two hands using the thumbs and the first two fingers as shown in figure #4. Pull out the ends of the shields slightly and at the same time apply a light pressure on the sides of the shield as indicated by the arrows in the drawing. Then replace the shields and observe that they fit tightly. In addition to assuring positive contacts, this will also prevent the shields from rattling.

LINE UP CAPACITOR ADJUSTMENTS
To align the circuits of this receiver it is essential to use a high grade modulated test oscillator, the output of which can be continuously varied with absence from overload when the individual circuits of the receiver are set into alignment. A conventional output meter can be connected across the terminals of the speaker voice coil to determine when the circuits are aligned. The selectivity of the output meter must be sufficient to give satisfactory readings with a low input signal. Before attempting to align the receiver, the service man should familiarize himself with the general layout of the chassis, the location of the tubes and various alignment condensers. Top and bottom views of the chassis are shown in figures #2, #3 and #4 and should be carefully studied before the actual work is started.

ADJUSTMENT OF I.F. (465 K.C.)

1. Set volume control or full and turn tone control to the bass position.
2. Connect output meter across voice coil of speaker.
3. Set test oscillator to 465 K.C. and adjust its output to produce a measurable reading on output meter when test signal is applied to the grid of the 6K7 I.F. tube thru a .5 mfd blocking condenser.
4. Adjust trimmer #42 to maximum output, reducing output of test oscillator as required.
5. Apply test signal to grid of 6A8 detector-oscillator and adjust #44 and #46 to maximum output.

ADJUSTMENT OF BROADCAST BAND
1. Set wave-change switch to the Black or broadcast Band position.
2. Set test oscillator and dial indicator to 1600 K.C.
3. Apply test signal to antenna terminal of chassis thru a .0002 mfd. series condenser and adjust #31, #19 and #8 to maximum output.
4. Set test oscillator and dial indicator to 570 K.C. and adjust #37 to maximum output.
5. Return to 1500 K.C. setting with both test oscillator and dial indicator and readjust #31, #19, and #8 for accuracy.

ADJUSTMENT OF GREEN BAND
Note: in adjusting the two short-wave Bands (Green and Red) a .0002 mfd. condenser and a 400 ohm resistor connected in series should be inserted in the high side of the test oscillator leads. This condenser-resistor combination is the approximate equivalent of a short wave antenna.
1. Set wave-change switch to the Green Band position.
2. Set test oscillator and dial indicator to 5500 K.C. and adjust #30, #18, and #7 to maximum output.
3. Set test oscillator and dial indicator to 1900 K.C. and adjust #36 to maximum output.
4. Return to 5500 K.C. setting and make readjustments of #30, #18, and #7.

ADJUSTMENT OF RED BAND
1. Set wave change switch to the Red Band position.
2. Set test oscillator and dial indicator to 17000 K.C. and adjust #29, #17 and #6 to maximum output.
3. Set test oscillator and dial indicator to 6000 K.C. and adjust #35 to maximum output.
4. Return to 17000 K.C. setting and make readjustment of #29, #17 and #6. Note: The adjustment of the two short-wave oscillator lag condensers (#35 and #36) is best made by the max-max method. This is done as follows:

Tune the receiver with the left hand by means of the tuning knob and adjust the lag condenser in either direction and then without changing it, tune the receiver thru a maximum, noting reading on the output meter. Change the lag condenser further in the same direction return receiver and not reading. If the output drops with the second adjustment, reverse direction of the adjust of lag condenser. Continue the type of trial and error adjustment until no further improvement can be made when either the tuning control or the lagging condenser are changed. While this procedure may appear to be difficult, facility can easily be acquired by practice and the operation requires only a few minutes.

IMPORTANT: While testing or making repairs on this receiver, the chassis should not be turned upside down or on its side for any long period of time while the set is turned on as the chemicals in the electrolytic filter condenser will come out thru the air vents making the condenser appear to be defective. If the set is left in this position too long the condenser may be injured.