There were two generations of control woofers for the IRS Beta/Gamma system, and they could be identified by the presence or absence of that resistor. They are comparable in actual operation. You can test whether the servo is working properly by gently pressing the control woofer cone while the LF amplifier is on and no audio signal is going to the woofer. You're in good shape if the column's other woofers move in sync with the control woofer.
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Primary sources: VPI TNT III/SDS turntable, SME-V arm; Bryston BDP-3 digital player; Bryston BDA-3 DAC; McIntosh MVP-881 disc player; McIntosh MR-80 tuner. Preamplifier Audio Research Ref 5SE; Audio Research Ref Phono 2SE; Moon 430 HA. Amplifiers Conrad Johnson Premier 1B; Audio Research D-300; Bryston 4B. Speakers Infinity IRS Beta. Recorders Tandberg TD20A; Crown SX-822; Nakamichi 670ZX; Alesis Masterlink ML-9600. Power Tice Power Block/Titan (x2); McIntosh MPC1500; API Ultra II-20; multiple 20A derated dedicated lines.
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