Buick Motor 980660 Schematic

Buick Motor 980660

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Product Information:
Model:980660
Manufacturer:Buick Motor (United Motors Service)

Schematics Content

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IF PEAK 455 KC

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Fig. 4 - Parts Layout - Bottom View

TUBE VOLTAGE CHART
Bottom View

* All voltages given should be checked with band selector switch set in the broadcast band position except (6SK7, Tube No. 3) as noted on sketch.

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CIRCUIT ALIGNMENT

ALIGNMENT PROCEDURE: The adjustable trimmers and iron cores in this receiver have been very carefully adjusted at the factory and should require no further adjustment (except the antenna trimmer item L), unless tampered with or a defective unit has been replaced. It is, therefore, advisable not to attempt any adjustment unless it is definitely known that an adjustment is necessary.

Should realignment be necessary the circuits can be properly adjusted only by the use of a calibrated test oscillator or signal generator and an output meter.

To align the circuits of this receiver correctly, an accurately calibrated oscillator or signal generator and an output meter must be used. In aligning this receiver it is very important that the correct frequencies be used and that all alignment adjustments be made in sequence specified below starting with the I.F. Amplifier, then aligning the broadcast band and finally the short wave bands. Slight misalignment of either the I.F. or R.F. circuits will result in a loss of sensitivity over most of the dial.

All R.F. and IF. adjustments are accessible after removing the speaker cover and rear cover. The I.F. primary windings are adjusted by iron core screws B, D, F, located on top of the I.F. transformers, Fig. 3, and the secondary windings A, C, E are adjusted by core screws located at the bottom of each I.F. transformer, Fig. 4.

1. Aligning I.F. Stages at 455 K.C.

(a) Connect output meter across the voice coil of the speaker.

(b) Connect the high side of the signal generator to the grid of the second I.F. tube 6SK7, (Pin #4, Fig. 2) through a .01 mfd. condenser and the low side of the signal generator should be connected to the frame of the chassis.

(c) Turn the volume control on full.

(d) Adjust signal generator to 455 K.C.

(e) Adjust core screws (Illus. A & B, Figs. 4 & 3) on the 3rd I.F. transformer for maximum reading on the output meter.
NOTE: Always use the lowest signal generator output that will give a reasonable deflection on the output meter.

(f) Connect the signal generator lead through the .01 condenser to the grid of the first I.F. tube 6SK7, Pin #4 and adjust core screws (Illus. C & D, Figs. 4 & 3), in the 2nd I.F. transformer for maximum output as in (e).

(g) Connect the signal generator lead through the .01 condenser to the grid of the tube 6SA7, (Pin #8) and adjust core screws (Illus. E & F, Figs. 4 & 3) in the first I.F. transformer for maximum output.
NOTE: These adjustments should be repeated several times and during alignment, the signal generator output should be kept to as low a value as is consistent with obtaining a readable indication on the output meter.

2. Broadcast Band Alignment

Six trimming adjustments are provided which include trimmers L, K, J, associated with Illus. #2, 3, 4 and the three iron cores I, H, G, which are mounted in front of the coil assemblies in conjunction with the core draw bar. If realignment, is found necessary, the R.F. circuits should be adjusted in the following sequence:

(a) Tune the receiver to the extreme high frequency end of the dial and against the stop.

Fig. 6 - Trimmer Locations

Fig. 5 - Dial Cord Layout

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5. Adjusting Antenna Compensating Condenser
This adjustment should only be made after the receiver has been properly installed in the car with the antenna connected to the receiver. Tune the receiver to a weak signal at the high frequency end of the broadcast band at about 1200 K.C. and with the antenna fully extended, adjust the antenna compensating trimmer (Illus. L, Fig. 6) for maximum signal strength.
Do not attempt to make any other alignment adjustments with the receiver installed in the car.

(a) Remove speaker (front) cover, rear cover and the bottom of tuner section. Unsolder the connecting leads from the volume control and other points in the chassis.
(b) Remove the link and arm arrangement that operates the band switches by first removing the two units, (A), holding the short link arm (B) to the band indicator shaft.
(c) Remove screws (C) and link arms (D) from each of the band switch shafts, but in removing the center one, care should be taken not to lose the two steel rollers and "S". spring (which are loose on the assembly) from the detent device at the base of the center coil unit.
(d) Remove the four units (B) which hold the coil plate (F) to the tuner assembly and withdraw the coil plate from the assembly, being careful to prevent the coil cores from striking any part of the assembly which may result in breakage of the core.
(e) After removing the two small screws located at the base of each coil unit, the coil units can then be removed from the coil plate. In re-assembling the cores into the coil units, hold the coil plate (F) slightly " off-square " from the cores, then insert the core nearest its coil, one by one, as the coil plate is brought square with the tuner assembly frame.

REMOVAL OF COIL UNIT
Should it become necessary to remove a coil unit, the following procedure should be followed:

Adjust trimmer G to match car antenna (1430 XC) when radio is installed.

Rock gang condenser back and forth through signal during 600 K.C. adjustment of screws H & J. See Bulletin 6D-2 for complete Alignment Procedure.

PUSH BUTTON SET - UP

Release holding spring in bottom of button, pull button off. Loosen re-set screw, tune in desired station. Push in re-set screw until it bottom. Release and tighten screw. Replace button.