PART Ill—ELECTRICAL TESTS
(1) TESTING CONDENSERS
Most of the condensers in Radiolas 21 and 22 can be tested by the continuity tests given in Part III, Section 3.
If further tests are desirable the large 1 mfd. condensers may be tested by charging them with the highest "B"
voltage available and then shorting their terminals with a screw-driver. An O.K. condenser will give a good. spark
when such a short is made. A leaky condenser will give no spark and a shorted condenser will give a spark when an
attempt is made to charge it.
Small condensers may be click tested for shorts or conveniently replaced by new-ones to check on their
operating condition.
(2) VOLTAGE READINGS
The
following voltages taken at the sockets are correct for
batteries when new. A 25 per cent drop is permissible before
renewal is necessary. Individual batteries may be tested by dis-
connecting entirely and reading with a voltmeter. The "B"
batteries should be discarded when their voltage is less than 34
volts per block. The "C" batteries should be renewed with the
"B" batteries. A storage "A" battery requires charging when the
voltage is below 5.4 for a battery or 1.8
per
cell
under load.
SOCKET VOLTAGES
RADIOLA 21 OR 22
Radiotron UX-171A used in last stage with 135 volts plate
supply. For other power tubes or plate voltage the change will be
in last socket
Figure
5—
Internal connections of A.F.
only, all
other voltages remaining the same.
VOLUME CONTROL AT MINIMUM
Socket No.
Filament Volts
Filament to
Control Grid Volts
Filament to
Screen Grid Volts
Filament to
Plate
—Volts
Plate Current
Millamperes
1
3.2
1.6
0
135
0
2
3.2
1.6
0
135
0
3
5.0
—
—
45
3.5
4
5.0
9
—
125
6.5
5
5.0
27
—
130
15
10
YELLOW
BLUE
Figure 5—Internal connections of A.F.
Coupling Unit
YELLOW
BLUE
