Poly-Pedance Modulation Transformer Instructions

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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Modulator Stage

Class C Load Impedance

Primary

Series Coils

Parallel Coils

Join 9-12 8-11 9-12 9-11 3-6 3-6 3-5 7-11 8-12 7-12 1-5 1-6
Join 8-10 9-11 9-10 2-4 3-4
P-to-P Impedance (Ohms) P B-B P Connect To 8-11 7-10 7-11 7-10 1-4 2-5 1-4 7-8 8-9 7-9 1-2 1-3
2000 1 3-6 4 1300 254 2000 1150 325 675
2000 2 3-6 5 4320 835 6600 3840 210 1070 2240
2000 1 2-5 4 6400 1230 9500 5650 308 1590 3320
2000 7 9-12 10 1470 445 780 370
2000 8 9-12 11 3100 930 1600 155 770
2000 7 8-11 10 4800 810 4000
3000 1 3-6 4 1950 380 3000 1730 487 1010
3000 2 3-6 5 6500 1250 10k 5760 315 1600 3360
3000 1 2-5 4 9600 1850 14.4k 8500 460 2380 5000
3000 7 9-12 10 2230 670 1170 560
3000 8 9-12 11 4650 1400 2400 235 1150
4000 1 3-6 4 2600 500 4000 2300 650 1350
4000 2 3-6 5 8650 1670 12200 7680 420 2140 4480
4000 1 2-5 4 12800 2460 19000 10300 615 3180 6600
4000 7 9-12 10 2940 890 1560 740
4000 7 8-11 10 9600 1620 8000
5000 1 3-6 4 3250 635 5000 2880 812 1690
5000 2 3-6 5 10700 2090 16600 9600 525 2680 5600
5000 1 2-5 4 16000 3080 14200 770 3980 8300
5000 7 9-12 10 3700 1100 1950 920
5000 8 9-12 11 7700 2330 4000 390 1900
6000 1 3-6 4 3900 760 6000 3450 975 2020
6000 2 3-6 5 13300 2500 11500 630 3200 6730
6000 1 2-5 4 3700 17700 925 4780 10000
6000 7 9-12 10 4450 1330 2340 1100
6000 8 9-12 11 9300 2800 4800 470 2300
6000 7 8-11 10 14000 2400 12000
8000 1 3-6 4 5200 1020 8000 4500 1300 2700
8000 2 3-6 5 17400 3340 15400 840 4280 9000
8000 1 2-5 4 4900 20600 1230 6350 13300
8000 7 9-12 10 5950 1770 3120 1480
8000 8 9-12 11 12300 3700 6500 625 3100
8000 7 8-11 10 19000 3200 14000
10000 1 3-6 4 6500 1270 10000 5750 1620 3380
10000 2 3-6 5 21600 4180 19200 1050 5350 11200
10000 1 2-5 4 6150 1540 7950 16700
10000 7 9-12 10 7400 2230 3900 1850
10000 8 9-12 11 15500 4700 8000 780 3850
12000 1 3-6 4 7800 1520 12000 6900 1950 4050
12000 2 3-6 5 5000 1260 6400 13400
12000 7 9-12 10 8900 2700 4700 2200
12000 8 9-12 11 18500 5650 9600 940 4600
14000 1 3-6 4 9100 1770 14000 8050 2270 4720
14000 7 9-12 10 10400 3120 5480 2600
14000 8 9-12 11 21700 6500 11000 1100 5400
16000 1 3-6 4 11000 2015 16000 9200 2600 5400
16000 7 9-12 10 11900 3560 6250 3000
16000 8 9-12 11 7500 13000 1250 6200
18000 1 3-6 4 12500 2280 18000 10200 2800 6100
18000 7 9-12 10 13400 4000 7000 3300
18000 8 9-12 11 15200 1400 6950
20000 1 3-6 4 13000 2540 20000 11500 3240 6760
20000 7 9-12 10 14800 4460 7800 3700
20000 8 9-12 11 9400 16000 1560 7700

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19 January 1999