Changing region band on Nakamichi SR-40?

Discussion in 'Tuners' started by filmis, Oct 16, 2017.

  1. filmis

    filmis Active Member

    Messages:
    116
    Hello,

    I've got the Nakamichi SR-40, which is the Japanese variant of the SR-4. I've gotten everything to work except for one thing: the tuner is set to the Japanese broadcasting frequency range, which is 75-90MHz. There's only one station I can pick up in this range, and it's a Christian rock station. As enlightening as that may be, from time to time I imaginably will want to listen to something else!

    I have managed to get the Toshiba TC1647BP chip to operate in the North American frequency range by setting pins E1 and E2 to high, where previously they were low. While I can search up and down the whole frequency range, the tuner stays permanently, and badly, tuned to a single station. I've followed the schematic and datasheet to the letter and I just can't seem to get this to work. VT stays at a constant 30.50V. I know I haven't done any damage because I can go back and switch it back to the Japanese range and it'll tune correctly then, with VT changing as it should.

    Any ideas or suggestions?
     
  2. rcs16

    rcs16 Super Member

    Messages:
    2,965
    Location:
    Baldwin, Ontario, Canada
    Little bit more to it than just the PLL LO VCO range, the RF tuned ckts have to center on the freq range in question, 88-108MHz and the LO has to have a range of 88-108MHz + 10.7MHz IF offset. It is a lot of work and requires you to understand the design completely, re-wind coil/transformers, not an easy job for a hobbyist.
     
    Last edited: Oct 31, 2017

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