PREAMPLIFIER ANALYSIS FOR CONSOLES PRIOR TO USE OF THE AO-10
It is suggested that amplifiers used in the Hammond Organ be tested with a
conventional radio set analyzer with AC and DC voltage ranges up to 500 volts, and
current ranges up to 100 milliamperes. With this flexibility the instrument may also
be used as a tube tester and a line voltmeter. A resistance scale on the analyzer
meter or a separate meter with self-contained battery is useful for testing
resistors in the amplifiers. It should have a scale reading up to 3 megohms.
Typical readings for an analyzer with a 1000 Ohms per Volt meter are given below.
The voltages may vary slightly if readings are taken with a meter of different
sensitivity or with ranges in variance with those specified.
Weston Model 772 type 2 analyzer is satisfactory for all necessary tests of the
organ, and when combined with a tube checker in Weston's Model 775 it is a complete
portable service set adequate for the Hammond technician.
If a discrepancy of 20% or more is noticed on any of the above readings, an
investigation should be made of al1 parts which might affect it. Any resistor
differ1ng by as much as 30% from its rated value should be replaced. A condenser
should be replaced if its capacity has dropped as much as 20%.
For testing both generator and ampl1f1er condensers, a neon lamp type tester is very
satisfactory. Such a tester should be capable of check1ng both electrolytic and
paper condensers of capacities ranging from .001 to 30 microfarads. In every case,
condensers must be disconnected before test1ng, otherwise the read1ng will be
affected by other parts of the circuit.
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