KT 6007 stereo beaon

Discussion in 'Tuners' started by calman46, Apr 19, 2017.

  1. calman46

    calman46 AK Subscriber Subscriber

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    Capture.PNG I've trying to figure out why the stereo beacon won't light on my recapped Kenwood KT 6007. The beacon didn't work before the recapped.. The only voltage I don't have is on the collector of Qc13 (MPX PRE amp board). The tuner plays fine . The original Qc12 &Qc13 diode tested good (replaced anyway ,didn't work) . Qc4, Qc5 &Qc15 all diode tested good . I also notice that my unit is not wired like the schematic . The Auto FM is not wired at all. It seems the when the mono button is pushed in it grounds pin 8 of the HA1156 to ground which puts the chip into mono . I'll see if I can post the schematic ,my file is to large .
     
    Last edited: Apr 19, 2017
  2. Punker X

    Punker X AK Subscriber Subscriber

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    Other things can cause the stereo lamp to not light. It not aligned correctly. Don't have time this morning to download the manual. Primarily look at the MPX, discriminator and muting adjustments. All these can keep the tuner from lighting the stereo lamp. Should also ask, does it receive in stereo and the lamp is just not lighting, or is it always in mono?
     
  3. calman46

    calman46 AK Subscriber Subscriber

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    I was using Kenwood while I recapped a Pioneer TX 9100. I would say the Kenwood was playing in stereo but I'm not a 100%. The muting is strong it has to be a good strong signal to get through it . I have the SM on CD .The 19kHz pilot is there . I did the beacon test from alignment chart,but I used a strong FM signal and I only add 0.365VDC on TP5 . I have a scope and freq, counter but my frequency generator is to old for this .
     
    Last edited: Apr 20, 2017
  4. calman46

    calman46 AK Subscriber Subscriber

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    I hooked it back up and I think its always in mono . Switching between the auto FM and mono doesn't seem to have any affect on the sound.
    I have the 19kHz on P#10 (HA1156) if I'm understanding the block diagram I am also suppose to have 38kHz on P#4 & P#5 (HA1156) I don't . Tested with no station and frequency counter.
    I'll try a new HA1156
     
    Last edited: Apr 21, 2017
  5. chazix

    chazix AK Subscriber Subscriber

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    Well, at my day job, things are pretty slow, so perhaps I can contribute something.

    I'm not sure whether you understand that it is exactly the intended function of QC12 and QC13 to serve as a "gate" on stereo decoding. If you don't have a high voltage on the collector of QC13, I think the most likely reason is that there is not enough IF signal strength to "open the gate".

    The input to the "gate" is an IF signal strength voltage coming from IF board pin 10, labelled "BEACON". (Assuming that the schematic that I have is a match for your tuner.) You could try adjusting VRb3 to see whether you could force the signal strength voltage to a level high enough to put the tuner into stereo mode. However, I recommend that you take note of the original position of VRb3, so that you can return it to the same position later. It is very unlikely that the problem is merely a misadjustment of VRb3.

    If you do get stereo mode in the above experiment, then the question becomes "why is the IF signal strength voltage too low?" There are many possible reasons, but I think it is most likely that the tuner's IF and/or RF stages are not in good alignment.

    I hope this is helpful. Cheers,

    chazix
     
  6. calman46

    calman46 AK Subscriber Subscriber

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    Thanks chazix , I'll check it out
     

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