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Sony STR-V4 won't do FM stereo,anything I can do?

Discussion in 'Tuners' started by Blue Shadow, Jan 5, 2018.

  1. Blue Shadow

    Blue Shadow I gotta get me a new title

    Messages:
    21,030
    Location:
    SE PA
    This STR-V4 doesn't have an SM online. TheV4L is there but the tuner board is different. I checked and the STR-V3 has the same tuner board as the V4 I have. I'll attach some shots of it. Full manual is on HFE: https://www.hifiengine.com/manual_library/sony/str-v3.shtml

    I understand that a tuner probably needs alignment all these years after it was built but I'd like to see if I can get that nice red stereo indicator to light up again without that service which I can't do.

    Thanks for any recommendations on making the lamp light again. The bulb is good and has been tested. There is no voltage at the Stereo Lamp connection.
    V3-1.jpg

    V3-2.jpg

    V3-3.jpg
     

     

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  2. Punker X

    Punker X Moderator Moderator Subscriber

    Messages:
    3,981
    Location:
    Panic in Detroit
    Discriminator and VCO are going to be the adjustments most likely to cure your issue. Although, can also be affected by muting adjustment or issue. Misalignment in the front-end and IF can also affect the it by to a lesser degree
     
  3. Blue Shadow

    Blue Shadow I gotta get me a new title

    Messages:
    21,030
    Location:
    SE PA
    Well I have found the SM for the V4 and it agrees with the one for the V3 as shown above but I'm having no luck getting things right.
    I tested Q202 in situ and it did the double diode with one set of connections so thinking this c1364 transistor is ok, it is the muting transistor. Since I'm limited on FM test gear, I can't tell what signal level is going into the unit but the muting will cut almost all signals on a folded dipole antenna.

    Without the unit wanting to go into stereo, I don't get anything on the test points for the 19kHz carrier signal. I guess this unit needs to see someone that actually knows something about how to tune a tuner. Until then, mono radio and nice Phono with a high level input and 55wpc are the capabilities of this unit.
     
  4. rcs16

    rcs16 Super Member

    Messages:
    3,905
    Location:
    Baldwin, Ontario, Canada
    I'd have to look at the manual to see what they use
    Std older design using a HA1137 quad detector and HA1196 st decoder.
    Similar to a pioneer sx-650
    follow the tuning procedures and tests, no simple answer, could be any one of a n umber of components in the affected area, check for forced mono, killing of the HA1196 VCO, IC301, pin 16
    S3-2 is the St_Mono switch, grounds ic301-10 thru R313 to force mono
    they printed all the HA1196 pin bias voltages, they can be checked as well.
    Lots to check :)

    Good luck
     
    Last edited: Oct 18, 2018 at 8:51 AM

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