Well done!!! I found what I need to have, indeed!
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Regards, Maurizio
Great Manual. It was exactly what I was looking for
Text excerpt from page 15 (click to view)
6. Bias Current Adjustment
1. Set Test tape (Type 1 tape: UD-1) into the unit, input 1.25 kHz/12.5 kHz 21mV signal to JK1 LINE IN and record this signal on the tape. 2. Playback the recorded signal, and adjust RT103L (Lch) and RT103R (Rch) so that the level difference between both frequencies becomes within the range of 28mV + 2dB ~ �0.5dB on the voltmeter at JK1 LINE OUT. Remark: Unable to monitor waveform at line out during recording mode.