Pioneer CT-F950 Bias Problem

Discussion in 'Pioneer Audio' started by 1mike161, May 16, 2018.

  1. 1mike161

    1mike161 New Member

    Illinois near St. Louis MO
    My Pioneer CT-F950 is not recording properly on the Left channel. The recorded level of the left channel is significantly less than that of the right. I think I have traced the problem to the bias amp.

    I determined that the recording signal is good (balanced on all tape types and across many frequencies) all the way to the recording heads. Following the service manual, I shorted the base of Q303 to ground (I believe this turns off the bias signal) to measure the recording signal to the heads. All good at this point. Next, I checked the left and right bias signal channels and found that the left channel was significantly less than the right.

    Within the bias circuit, the signal problem occurs after the "Matching Transformer" (I believe this is an impedance matching coil). The next component in the circuit is a 330 pF capacitor and I believe it might be the Polystyrene Film type.

    My questions are, should I replace the coil or the capacitor or both? I would think that the capacitor is the more likely problem, but I'm not sure. Are there any precautions to take? I think Polystyrene Film caps are susceptible to heat. Are there viable substitutes....


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