Kenwood TS-990S Service Manual
Also see for SP-990: Instruction manual
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TS-990S13CIRCUIT DESCRIPTION3-5. Preamplifier circuitThe preamplifier circuit consists of two amplifiers: pre-amplifier 1 and preamplifier 2. Preamplifier 1 operates at30kHz to 21.5MHz, and has a gain of approximately 9 dB.Preamplifier 2 operates at 21.5 to 60MHz, and has a gain ofapproximately 22 dB.Preamplifier 1 is a noiseless feedback amplifier of thetransformer-feedback type, and incorporates a push-pull cir-cuit in order to improve the IMD (Intermodulation Distortion)characteristics. Preamplifier 2 uses a bipolar transistor (Q20)and forms a grounded emitter circuit.The preamplifier can be passed by turning off the P.AMPdisplay with the [P.AMP] key (Refer to Table 8.).Fig. 8 Preselector circuitATT ATT0dB1dB2dBPRESEL AMPRX unit(X55-313 A/2)PRESEL unit(X42-343 B/10)PRESELthrough pathPreselector circuitFig. 9 Configuration of the preamplifierPRE AMP2OFFPRE AMP1OFFFig. 10 Preamplifier 1 circuitL39L32L33Q25Q26L3414V14VL4414VL4014VOutputInput1t3t5t4.5t4.5t4.5t4.5t1t3t5t |
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