Kenwood KT-3300d Alignment Question
- Thread starter kenwoodm2a
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kenwoodm2a
Member
rest there procedure for now, try my tests
do not use the scope. measure the quieting sensitivity, that is an un-modulated carrier, muting off on the tuner, rf off, use your AC voltmeter, no filters, to monitor the noise on either L or R o/p, it jumps around like it should but you can average it out, increase rf level to get your -3dB, and so on quieting curve to the noise floor of the tuner. you can measure this quieting sensitivity at low mid and high band. post them. compare to what they say it should be in the specs.
I would be more than happy to try your tests but please keep in mind that I am no expert, just an amateur, so I'm having trouble understanding what your asking me to do. Could you please be more descriptive with the wording?
Thanks!
kenwoodm2a
Member
I'll keep trying what you suggest .....I would really like to actually see the change happening on the scope. If this is the normal way to adjust then there is no reason why I should having a hard time seeing it on my scope unless I am doing something terribly wrong.
What are your suggestions for procedure # 10 as far as the 10Hz 100-150kHz dev goes? How I'm suppose to get 100-150 kHz dev modulation if my generator only modulates as high as 100 unless I am completley misunderstanding the set up........
Thanks!
To measure the quieting sensitivity, you use an un-modulated carrier, so on your RF SG modulation is off.
No rf input signal. connect your audio out to a AC voltmeter (no scope). you can also connect this audio out thru an amplifier into a speaker to hear this noise.
set the ACVmeter to see this noise on the appropriate scale. you can adjust the level so it becomes your 0dB reference.
set the rf to 98.1MHz, rf off, connect to tuner, set to 98.1Mhz, muting off, noise on the ACVM should be the same, as above, using 0.1dB RF level increments, start from around -10 dBuV increase the RF level in small steps. witness as the rf level increases, the tuners audio starts to quiet the noise, you can determine what rf level quiets the audio noise by 3dB as so on 20dB etc, to the noise floor, as you increase the rf sig level. At around > 50-100uV the noise should be at the noise floor
Hope this makes sense for you.
No rf input signal. connect your audio out to a AC voltmeter (no scope). you can also connect this audio out thru an amplifier into a speaker to hear this noise.
set the ACVmeter to see this noise on the appropriate scale. you can adjust the level so it becomes your 0dB reference.
set the rf to 98.1MHz, rf off, connect to tuner, set to 98.1Mhz, muting off, noise on the ACVM should be the same, as above, using 0.1dB RF level increments, start from around -10 dBuV increase the RF level in small steps. witness as the rf level increases, the tuners audio starts to quiet the noise, you can determine what rf level quiets the audio noise by 3dB as so on 20dB etc, to the noise floor, as you increase the rf sig level. At around > 50-100uV the noise should be at the noise floor
Hope this makes sense for you.
kenwoodm2a
Member
I will try this sometime this week on my days off . I think I'm following what your asking me to do.
Like I said, I'm an amateur at this compared to you guys that have years of experience, so what comes naturally to you takes me more time to figure out.
If you don't mind me asking, once I perform this test, what conclusions will I discover from the results?
kenwoodm2a
Member
The number conversion for me has more to do with some of the alignment settings like the strength meter and the stereo indicator. I know it's not the end of the world if it's not exact but I'm just trying figure if I have it right. Must be my Scorpio nature of seeking perfection
Step 10 is adjusting the tuning meter. Not sure why they would want 10hz modulation at over 100%. Think this is a translation issue thing. The way I did it. Since you are adjusting the tuning meter. says plus and minus 100 to 150khz. Center tune to 98Mhz. Step the signal meter frequency up and note where the off tunes to the red bars. Go up and then go down and adjust VR2 so they change over at the same spot above and below 98Mhz.
kenwoodm2a
Member
kenwoodm2a
Member
OK, just so I'm clear, I need to set both my generator and tuner at 98Mhz . So then are you saying to manually vary the generator RF by plus and minus 150kHz or vary the tuner by that amount? I do understand where your going with this, I'm just not clear which one I'm suppose to vary .
When I did attempt this last week before your suggestion, I had fed an external 10 Hz signal into my generator as per the procedure which caused both red bars on each side to flicker at 10 Hz. If I adjusted VR2 during this time, I could adjust so that both red bars were both on and equally lit . If I varied VR2, one or the other red bar would turn off . As I lowered the modulation from 100khz down to 50khz, I could even tweak it better .
kenwoodm2a
Member
Gotcha! Thanks!
kenwoodm2a
Member
So I just had a question come through my mind and I'm not sure why I didn't think of this sooner.
Most of the measurements are being taken from the audio outputs which makes sense for distortion readings on the audio signal BUT, shouldn't the audio outputs only contain...........Audio??
Why are we able to see the RF carrier being modulated on the scope from the audio outs?
Shouldn't all the high frequencies above the audio range be filtered out before reaching the preamp?
Most of the measurements are being taken from the audio outputs which makes sense for distortion readings on the audio signal BUT, shouldn't the audio outputs only contain...........Audio??
Why are we able to see the RF carrier being modulated on the scope from the audio outs?
Shouldn't all the high frequencies above the audio range be filtered out before reaching the preamp?
It's always best to try to understand what you are doing in an alignment, versus just following cookbook steps. Personally I don't use distortion readings to align the RF front end, mostly because I use an FFT to look at distortion. But I do listen to the noise level (of the audio out jacks played through speakers) and look at the audio signal to "find the center of the IF channel". This mostly applies to analog mechanical cap tuners, as you have infinite adjustment there. For digital tuners, you can step the generator off frequency slightly to make sure your tuner is centered. If it's not, the fixes are varied depending on the tuner.
Once you are at the center, you can look at the IF signal to adjust the RF front end. But you need a scope and probe that has the bandwidth to do that. I use a 100 MHz scope/probe, so it's no problem. But you can also use the signal level output from the IF chip to an analog or digital voltmeter. You have to find that pin yourself, but it's not too hard. Or just use the built in meter and your ears. My experience says it's a lot easier to see changes in the lF signal level versus the audio signal for adjusting the RF front end.
Also to repeat what you already know - you started with a very advanced tuner to use for your first alignment. You may need to back up and learn more by experimenting on more simple models, and then reading how FM receivers work to better understand what you are actually doing.
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kenwoodm2a
Member
I had a few minutes yesterday and used the input level of my Amber distortion meter along with the scope to check the front end alignment and was able to see a change when adjusting the coils . As Bob mentioned in one of his replies, it takes gross changes to see a difference . It took at least a whole turn of each coil to notice any changes and as ALL of you mentioned, I turned the output of my generator low enough to see noise on the 1 kHz audio output. All the coils were pretty much dead on from their factory setting. The trim caps were more sensitive to minor adjustments but for the most part, we're almost dead on themselves . I guess I must of done something wrong or had something not connected right the last time I tried this....
kenwoodm2a
Member
Thanks Bob,
First let me clear something up.
Back in the mid 80's, I took an electronics course and we covered audio gear as well as tuners as part of the course . So I do have a reasonable knowledge of tuners and how they work although I never did work as a tech in this field as I went on to work in another industry but always maintained my passion for electronics as a hobby. What I'm missing is the many years of hands on experience that you guys have working on tuners repairing and doing alignments and I'm very envious of the knowledge that you all have locked into your minds. Over the last couple years I refurbished 4 of my vintage Kenwood tuners including my very expensive, at that time, KRC-939 car deck that's in mint condition. That was actually the first tuner that I did an alignment on which also has C-Quam AM stereo . Of course my generator does not have the capability of aligning the stereo part of the AM section, I do have a C-Quam transmiter that I used to verify that all works as it should . The alignment of the FM section on that tuner was no where as complicated as this current one which is why I needed a little more help .
Over the last year or so, I did get a used Amber distortion meter and upgraded my scope from an analog 60mhz to a digital 200mhz in preparation for aligning all 4 of my tuners . Then over the last several months I dug out my old tuner course material and read through it all again to refresh my memory before attempting these procedures .
I appreciate your input as well as everybody else's when it comes to sharing your knowledge and tricks of the trade . As you mentioned, this tuner is an advanced tuner but I have no fear as I'm practising on my spare unit and feel confident enough to get it right . I did manage most of the alignments with no problems and documented all my changes and procedures. I just needed a little help with some issues and am greatfull for everyone's support .
kenwoodm2a
Member
Rick,
Here are the results of the test you asked me to perform.
I'm assuming I performed them correctly.....
I am displaying the output setting of my generator as it reads in dbu EMF.
I suck at converting db, dbu, dbu emf, dbm and anything else not mentioned......LOL!
No Ant input............AC Voltmeter reading......... .170 v
No modulation..............Start......... -20 dbu EMF............ .170
10 ............ .180
20 ............ .185
30 ............ .190
35 ............ .200
38 ............ .190
39 ............ .180
40 ............ .170
41 ............ .150
42 ............ .135
43 ............ .110
44 ............ .090
45 ............ .070
46 ............ .050
47 ............. .040
48 ............ .033
49 ............. .025
50 ............. .016
51 ............. .008
52 .............. .002
53 .............. NO NOISE FROM SPEAKER!
Not sure why there was an increase in voltage from 10 to 39 dbu EMF.
Attached is the spec sheet for this tuner.
I was able to get most of the alignment settings completed on my spare practice unit but am still having an issue with alignment procedures # 20 and 21 on the attached alignment sheet.
I used my Amber distortion meter for all other distortion readings and had no problem seeing the changes on the analog meter as I was adjusting the pots......as a matter of fact, most of the factory settings were dead on or very slightly off. But with procedure 20 and 21, I was not able to see any changes happen at all when adjusting the pots. Those procedures require me to feed a 10 khz into my generator which I did from the Amber and read for distortion but could not see any changes no matter what configurations I tried.
I did make sure I had the generator set for external input and was clearly able to to see the 10 khz signal at the audio output of my tuner on my scope. The generator selector was also set for MAIN and L as per the procedure.
I do have another generator that I had tried using to feed the generator with but had the same results. At first I thought perhaps the other generator output signal might have to high a distortion level which was not allowing me to see any changes when adjusting the pots but like I said, even the Amber generator is giving me the same results so I'm confused.
Update!..........
I looked over the attached schematic for the distortion cancelling circuit board where all of the distortion alignment pots are located.
Alignment # 20 and 21 pots are located on the lower left hand corner and each adjust the input of both halves of IC 15 .
So this is what I tried......I turned off the power and connected a test lead to pin 7 of the chip and connected to the distortion meter and tried once again to adjust VR 9 and was able too see great changes to the analog meter of the distortion meter. I set the pot for the lowest distortion level and it brought me to almost identical factory setting so I'm guessing I must be on to something.
I then did the same thing for pin 1 and VR 8 and I had the same results!
So my question is.......am I actually reading distortion and is it ok to do it like this?
And why the heck couldn't I get the same results at the audio output just like the rest of the distortion readings from that circuit board without having to go right to the chip pin out?
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Hi Roland,
You are providing absolute recovered audio voltage measurements in voltages, where I asked for a relative dB noise decrease (quieting action as measured on the Amber) vs an increase in un-modulated RF level and at 3 different freq on the dial.
Use the dB relative pot, to un-cal the Amber and make the no RF level noise set to a 0dB relative setting on the meter to act as your starting point.
You started at -20dBuV Rf level, so I would expect to see the RF level that achieves -3dB quieting ( noise level decrease on the Amber) and so on.
0dBuV=1uV
I can not see how increasing the un-modulated RF level would cause an increase in recovered noise, it should be the opposite.
You did find the noise floor, 20 *(0.002/170)log =-98dB, a very good figure.
I have never done a KT-3300d so I am not the best guy to answer your ? on the procedures.
Rick
You are providing absolute recovered audio voltage measurements in voltages, where I asked for a relative dB noise decrease (quieting action as measured on the Amber) vs an increase in un-modulated RF level and at 3 different freq on the dial.
Use the dB relative pot, to un-cal the Amber and make the no RF level noise set to a 0dB relative setting on the meter to act as your starting point.
You started at -20dBuV Rf level, so I would expect to see the RF level that achieves -3dB quieting ( noise level decrease on the Amber) and so on.
0dBuV=1uV
I can not see how increasing the un-modulated RF level would cause an increase in recovered noise, it should be the opposite.
You did find the noise floor, 20 *(0.002/170)log =-98dB, a very good figure.
I have never done a KT-3300d so I am not the best guy to answer your ? on the procedures.
Rick
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kenwoodm2a
Member
Hey Rick,
Let's try this again!
Same as before using the generator output in dbu EMF but Used the Amber level input, un-calibrated db pot to start at 0 db and increased generator output until there was a -3 db decrease on Amber. Did this for 3 different frequencies as you requested.
I assume that I did exactly as you requested .........
The upper frequency that I tested at 104.9 seemed a little off in comparison to the 2 lower ones as they were pretty much similar.
-20 dbu EMF= 0 db
- 87.5 mhz ................................98 mhz ...................... 104.9 mhz
- 40dbu EMF = - 3db ............40 = -3db ..................... 46 = -3db
- 44 = -10db ..........................44 = -10db ...................48 = -10db
- 48 = -20db...........................49 = -20db ....................50 = -20db
- 51 = -30db ..........................55 = -30db ....................58 = -30db
- 60 = -40db...........................65 = -40db ....................68 = -40db
- 70 = -50db...........................75 = -50db ....................79 = -50db
- 81 = -60db...........................85 = -60db ....................85 = -54db
Once I reached 85 dbu EMF, there was little effect on the Amber meter after 85.
Hope I got it right this time.
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