Voltage Readings; Internal Connections Of Filter Condensers - RCA Radiola 17 Service Notes

In general a defective filter condenser will be indicated by the plates of Radiotron UX-280
heating excessively, with the set giving weak, distorted or no reproduction and a loud hum. When this
condition is experienced, the condenser bank should be disconnected from the circuit and the
condensers tested with a reasonably high voltage, not over 200 volts. The correct way to test filter
condensers is to charge and discharge them, being careful not to come in contact with the terminals.
Figure 17 illustrates filter condenser connections.
3.5 MFD
3.5 MFD

(24) VOLTAGE READINGS

When checking a Radiola 17 for possible defects it is good practice to check the voltage of the
various sources of current. To do this a service man will need both an A. C. and a D. C. voltmeter, the
D. C. meter to be of at least 600 ohms per volt in resistance. The following voltages should be obtained
at the terminal strip when the set is in operation with full load on the socket power unit (Figure 4A).
The terminal strip numbers are from front to rear, No. 1 being closest to the front of the Radiola and
No. 11 closest to the rear.
Terminals
1 to 2
3 to 4
5 to 6
7 to 8
7 to 9
Gnd. to 10
7 to 11
11 to adjusting screw of TTX-171 potentiometer
1MFD
3.5MFD
Figure 17—Internal connections of filter condensers
Correct Voltage
'
20
3MFD
1.5 A. C.
2.5 A. C.
5.0 A. C.
45 D. C.
135 D. C.
165 D. C. (Approx.)
9 D. C.
30 D. C.
1MFD
2MFD