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