Quad FM4 tuner manual mod


2011-11-05 4:20 pm
This mod came about becuase could not get the 4 bit cpu MP4480 or the TMS1000
so made it a manual tuning ,up to now after a day no drifting, so removed the IC1 and pin 12 link to REF h just above the IC1 this puts a high on the enable IC6 allowing knob voltage to tune the variacs , ,, attached the drawing


  • hfe_quad_fm4_schematic_11000_on.pdf
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You can do this by just strapping pin 12 to pin 26 in the socket after removing IC1. Pin 13 should also be strapped to pin 5 to disable the AFC and definitely switch off the stored-station tuning voltage, but, as 405man said above, the better option by far is to fit the new CPU from Quad.

NB This thread should really be in 'Analogue Source'.
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