The table below provides connection data for Stancor Poly-Pedance modualtion
transformers - model numbers, A-3891 (15 watts), A-3892 (30 watts), A-3893
(60 watts), A-3894 (125 watts). Under the column headed Primary P-to-P
Impedance are listed the modulator plate loads most commonly used. The
body of the table contains the possible Class C loads for these specific
modulator plate loads. In the column adjoining the modulator plate loads
are listed the proper terminals to use for these loads.
Finding Intermediate Values Not Found in the Table
Quite often it is desired to use an intermediate value of plate load
not found in the table. For example, it is desired to match a pair if 6L6's
with a 6600 Ohm plate load to a 10 kOhm Class C load. In the column headed
Primary, 6000 Ohms is the closest plate load to 6600 Ohms. Therefore,
when using the 6000 Ohm primary listing as a 6600 Ohm primary, a secondary
listing of 6000/6600 or 0.909 times 10 kOhms (0.909 x 10,000) or 9100 Ohms
should be used. The nearest listed secondary load is 9200 Ohms. This combination
results in a mismatch of only one percent.
In making the primary connections, terminals
listed under P are the plate terminals and those listed under B
are the modulator plate voltage terminals. Secondary connections for Class
C loads are made according to the instructions at the top of the column
where the desired Class C load is found. If more Class C current must pass
through the transformer than the series connection
will carry, then a parallel connection must be used. A parallel
coil connection will carry twice the current of the series connection.
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