the "if-shift" ic-751 is identifiable by the concentric if shift/notch control (instead of pbt/notch).
remove the top and bottom radio covers. just on the top of the main board, under the top cover, to the left of the two 9 mhz if filters, you will see a lone brown (or black) wire going to a jumper pin. it is j17. simply remove the wire from the pin, and tape it so it will not short-circuit to anything. then you have pbt with the center at the detent at the top. you can still turn pbt off by turning the knob fully counter-clockwise, just like the if shift.
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如果你的是 if shift , 可改成 p.b.t ,
把频宽变窄 2.3k> .....1.xk,,,
