THE DUAL SPEED PLANETARY DRIVE In order to make the tuning of short wave broadcast easier, a dual speed drive is provided, giving a ratio of 96 to 1 with the knon, No. 10, in the OUT position which is exceptionally good for shortwave tuning, a ratio of 16 to 1 is provided with the knob, NO. 10, pushed " IN, " used for standard broadcast tuning. You can use this drive knob in the position you like best.
The mechanism of this drive is of the planetary type, using ball bearings, No. 15, housed between cantilever type spring housing, NO. 2. When the drive knob, NO. 10, is in * OUT position, the balls, NO. 15, operate direct on the drive shaft, NO. 1, which gives a reduction in speed on the pointers. when the drive knob, No. 10,18 at " IN " position the balls. No. 15, clear the drive shaft, No. 1, and a clutch, NO. 4, contacts drive pulley, No. 3, and gives a direct drive on shaft, No, 1.
If drive should ever alip on the " IN " position you will likely find that set screws, NO. 5, have become loose in clutch, NO. 5. To reset clutch place shaft, No. 1, at "OUT" position. You can tell when it is at "OUT" position by the feel at just after the ball, NO. 15, comes up the incline on the shaft, No. 1, it will locate in every shallow groove on the shaft, No. 1,489 that the clutch, No. 4,18 Against frame, No. 16, and then tighten set screws, NO. 5, securely.
If the band switch knob, No. 9, appears to have excessive backlash, you will generally find that it was forced when the switch was at end of its rotation and the set screws, NO. 12, are broken loose, tighten these screws and a backlash still appears, loosen screw and adjust bracket and screw, No. 14.
When placing knobs, NO. 9 and No. 10, on shafts, be sure knob, No. 9, clears cabinet approximately 3/64 and tighten set screw, No. 8, securely. with shaft, NO. 1, at the " IN " position place knob No. 10, on shaft No. 1, until it stops against knob No. 9, then pull to the front 3/64 inch and tighten set screw NO. 8, securely.

CASE ELECTRIC CORPORATION MARION, INDIANA

SERVICE NOTES
In the event of failure of the receiver, time mey often be saved by making a few preliminary checks before removal of the Chassis and speaker from the cabinet.
1. Check the antenna end ground connections both at the receiver and also at all points where joints have been made. Noisy operation can often be traced to faults in antenna and ground installation especially when the receiver has been connected to an old antenna.
2. Cheek the tubes. It a reliable tube checking Instrument is not at hand, secure a set of known good tubes and Inter change the tubes in the receiver, one at a time, until the defective tube is located. Low sensitivity can often be traced to gas or grid current in an RF, first detector or IF tube. Hum is often due to heater-cathode shorts in any one of the tubes.

If the above. checks do not disclose the reason for failure of the receiver remove the chassis and speaker from the cabinet and check the supply voltages as indicated on the chart. To assist in the location of the various tube prongs, the schematic diagram tube symbols have been so drawn as to represent the socket as viewed from the bottom of the chassis.

Hum, motorboating, low volume and low voltage may be due to shorted or defective electrolytic condensers.

Open bypass condensers often cause Oscillation or distorted tone. To check for this condition, shunt each condenser with another of similar capacity and of the same voltage rating until the defective unit is located.

Shorted bypass condensers cause low voltage or weak reception. Remove suspected unit and replace by one of correct capacity and rating.

In checking circuits connected to the electrolytic condensers it is necessary to observe the polarity of the leads of the continuity meter. Use the meter with the positive test terminal on the anode or plus side of the circuit. If the reverse connection is used the electrolytic condenser will become conductive and show a false low resistance reading.