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Each unit in the accompanying diagram carries a serial number. The values of these units are as follows: Condensers: A - 203,8 mfd. electrolytic; A. 304,.0001 mfd.; A - 30), special coupling; A - 306,.25 mrd.; A - 307,.006 mfd.; A - 308,.002 mfd. Chokes: C-102,505 turns; C-104, 1,200 turns, Resistors: R-102, volume control, 6,400 ohms with 200 ohms fixed; R-103, tone control resistor, special; R-203, center tapped, 15 ohms; R-310, 25,000 ohms; R-311, one megohm; R-312,200 ohms; R-313,5 me. gohm; R-514, 100,000 ohms; R-315, 50,000 ohms; R-316,3 megohms.
The ordinary set analyzer will not give correct voltage readings on the Musette due to so many readings having to be taken through high resistance, Evea a high-resistance voltmeter will not give a correct reading for the following circuits: C bias for 45 tube; detector plate voltage; screen grid voltage and grid bias; first audio plate and first audio C bias. A voltmeter with from 800 to 1,000 ohms resistance per volt should give a deflection on these circuits, but the reading will be reduced by the high resistances.
In checking to determine there are no open circuits, see that at least some reading is had on the above circuits, being sure the volume control is turned to maximum volume position Then read the following
Voltages which vary according to a-c. line voltage, being sure the antenna is disconnected and condenser shield is in position.
Chassis to plate prongs of the 1st and 2nd r.f. tubes and 45 output tube, from 190 to 210 volts.
Chassis to screens of ist and 2nd rf. tubes, from 75 to 110 volts.
Chassis to cathodes of 1st and 2nd r-f. tubes, should not exceed 5 volts.
Filament to filament of all tubes except 80, from 2.3 to 2.5 volts.
Between chassis and 80 filament, from 190 to 210 volts. Should this read 230 volts or more, indications are that the electrolytic condenser on rectifier side is shorted to chassis.
Across speaker field, from 100 to 110 volts. This reading checks the filter con denser and indicates that the speaker field is not shorted.
If all the above voltages are correct and some meter deflection is had on the other mentioned circuits, you can assume other voltages to be correct and look for the trouble elsewhere.
It will be seen from the circuit diagram that the tone control is made up of the con denser A - 307 and the variable resistor R-103. If variation of this control has no effect, the condenser is open. If a variation of this control to maximum low note position cuts out the received signal, the condenser is shorted.
If an exceedingly long antenna is used with the Musette it may well effect the
Tracking of the first rof. circuil. A 50 - foot antenna is recommended.
When adjusting for resonance, use the trimmers only at the bottom end of the dial and make the necessary adjustments with the trimmers open as much as possible. If they are screwed down tightly, there is a constant added capacity to the tuned circuit which might not allow the set to tune down low enough. The adjustment of the detector tuned circuit is quite critical and great Care should be taken in this adjustment.
Adjust at the top of the dial by bending the split fins on the rotor plates of the con. densers. When making these, as well as the trimmer adjustments, select a weak signal to work on.
In case of excessive hum, first determine whether it is in the chassis or the speaker by removing the 45 tube. If the hum stops, the trouble is most likely in the chassis. If the hum continues, it is probably in the speaker.
Hum in the chassis is usually due to either a defective 24 detector tube or electrolytic condensers either shorted, open, or not properly " formed. "
Hum in the speaker may be due to the hum bucking coil being connected up in the reverse manner. Therefore, first try reversing the bucking coil leads. These wires come out of the pot coil and go to the out put transformer mounted on the side of the speaker. Looking from the back, with the transformer at the left, the yellow upper in side connection and the black lower center connection are the leads which should be reversed.