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Kenwood KT-5300 tuner

Discussion in 'Kenwood-Trio/Kensonic-Accuphase' started by Tube Radio, Nov 26, 2018.

  1. Tube Radio

    Tube Radio Super Member

    Messages:
    3,476
    I've had a Kenwood KT-5300 tuner for several years and maybe a year or two after I got it while doing some probing the tuner went dead.

    I did some initial checks and put it aside.

    Fast forward several years to now I remember that I have the tuner and decided to see what was wrong with it.

    Checked the power supply and I got the main B+ voltage, but I got nothing on the positive of an electrolytic cap which I knew was not right.

    I looked in the service manual I downloaded and it was C48 where I did not get the voltage.

    Turns out Q7 was bad.

    I looked for my stash of transistors and didn't readily find it. I did see an old small defunct Sony amp which lo and behold just so happened to have the correct transistor.

    I installed it and the tuner now works.

    FM seems to be spot on. AM, however is off. Tuning in my part 15 AM transmitter which uses a 1MHz TCXO the dial is off to where it is received at the 101 MHz mark on the FM portion of the dial.

    I know the AM needs to be adjusted, but should I adjust the FM as well or leave it alone? I am tempted to tweak the alignment to ensure it is proper, but I don't want to mess with it because it may already be right.

    Also do I need to recap the tuner?

    It may replace a JVC T-X200 tuner in my smaller system.

    Is the Kenwood any better than the JVC? I'm not very fond of analog tuners as I am so used to digital tuners which have presets.

    If the tuner is better I will keep it and deal with no presets.

    Main thing I am considering is which tuner can receive more stations and receive them better.

    EDIT:

    While looking at the manual I saw where the output coupling caps are .1uF and there is a single 820K resistor to ground after each cap.

    With the input impedance of my McIntosh C-24 preamp being 250K that gives an impedance of 191.589K.

    As seen in this diagram a phase shift starts occurring at 120Hz even though frequency response is flat to 20Hz.

    Frequency response 1.png

    Now if I use a 2.2uF cap the phase shift starts at 20Hz and the frequency response is flat to .9Hz.

    Frequency response 2.png

    There any audible benefit to using a 2.2uF cap in place of the .1uF cap?

    EDIT 2:

    I found a couple 2.5uF caps so I tried those and the tuner at least is no worse sounding, but I honestly think the bass is better given there's no phase shift until 20Hz.
     
    Last edited: Nov 26, 2018

     

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  2. rickl

    rickl Active Member

    Messages:
    129
    Location:
    Twin Cities
    Hey Tube Radio, if you look at Doug's lovely resto sticky and dig into the KT-5500 resto, you will see the C45/46 .1 tant replaced with a 3.3 WIMA. Assuming this is the output cap (I don't have a schematic, just followed the recommendations) I think your 2.5uF is fine.

    I have a KT-5500 and it sounds great to me.
     
  3. Tube Radio

    Tube Radio Super Member

    Messages:
    3,476
    In mine it is C43 and C44 and the originals are mylar.

    3.3uF would necessitate the preamp have an input impedance of 150K in order to make the phase shift not start until 20Hz where the increasing phase shift under 20Hz won't matter.

    150K which is in parallel with the 820K resistor in the tuner will give an impedance of 126.8K as seen by the capacitor.

    This of course only applies to the KT-5300 as I don't know if the KT-5500 uses the 820K resistors.

    We then get this.

    Frequency response 3.png

    Not sure how much phase shift affects the sound, but I'm sure it has to affect it in some way shape or form.
     
    Last edited: Nov 26, 2018
  4. hopjohn

    hopjohn Silver Face Subscriber

    Messages:
    1,102
    Location:
    Dallas, TX
    The KT-5300 is pretty bare bones. If you're looking to take the time to recap it, I think you'd be better off getting a KT-7500 instead. The KT-7500 responds much better to upgrades and modification than the 5300 ever will. Upgrades to the 7500 have also been very well documented with proven results by the fellas over at fmtunerinfo.com. Why not take advantage of the groundwork that has already been laid out for you? I've done one personally, and while the upgraded 7500 will never take the place of a 600T, the end results are certainly worthy of the effort.
     
    Last edited: Nov 27, 2018
  5. Tube Radio

    Tube Radio Super Member

    Messages:
    3,476
    So far I'm well pleased with this tuner.

    I'd have to look for and buy the other tuner which if this tuner ultimately don't satisfy me i will do.

    Here's a short clip of audio recorded from the tuner.

     
    Last edited: Nov 27, 2018

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