Misalignment of tuners ?

Shivam

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I have come across this many times in various threads and forums.

What does misalignment in a tuner / radio mean ?
 
Yes, I do like vintage tuners. Turning the big knob and watching the slider move gives me a sort of satisfaction.
 
If you look at the dial then you will find the there are markings for frequency which are spread in one direction. Slider moves and indicates roughly what frequency you are receiving.

Due to internal misconfiguration of some parts tuner's indication and tuned frequency differs by large difference. Signal detection, stereo separation is bad. Sensitivity is bad, low powered weak signals could not be received. Some/all radio stations tuning range go out of dial and they could not be received at all.

All above problems could be cured with alignment of tuner. Alignment bring all stations in tuning dials range, signal pickup is increased.

In technical terms - selectivity and sensitivity improved with correct indication of tuned frequency.

Mostly mishandling, banging of tuner changes core positions in tuning coils and misalignment happens. Though this is analog only phenomenon happens in digitally tuned analog receiver also. Digital tuner also has some failure points but analog tuner has it always. Still I like analog tuners sound.
 
IMO each town or city in India used to have guy, with frequency generators and scopes. I have no idea who does it, but you can search locally. Previous radio manufacturers used to have service centres. Even my small town of 50,000 population had 2. (Unfortunately both died due to old age. RIP) Their kins scrapped all equipments.

For me it takes one month to align, thanks to absence for all above equipments.
First I gather service manual, study it. Then I pledge not to break anything - core or wire. Clean it and study for 1week. Replace necessary parts if any, mostly electrolyte caps on signal and PS. Then I use IF generator for AM FM and tune it. For signal generator I use another digital radio with outdoor antenna. With that frequency reference I tune frequency band. This could be only done after our TV, STB is switched off and before AM transmission goes off air - 9:30PM-11:00PM.
You should find someone locally who can do it for you.
Also if someone comes across AM FM generator, please let me know. Currently I use radio transmitter with digital tuning but I can not tune deviation, that is trial and error. I have basic IF DIY oscillator, 5 MHZ oscilloscope, FM transmitter, couple of DMM. So nothing special about it.
 
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I used to think that this was a simple error in the displayed frequency of the slider and the actual frequency. Thanks for the detailed information.

Now I have another question - why is that the analogue tuners suffer more from this than the digital ones ?
 
Now I have another question - why is that the analogue tuners suffer more from this than the digital ones ?

There is very complicated answer for this. Let me explain it in a simple way. Consider you have letter written on paper and want to send long distance. You will put it in some envelop with identification tag and sent. Receiver receives, removes envelop and read that letter.

Human/music sound is one frequency and you need to transmit in air for long distance. You put it on a carrier that is 88-108MHz for FM or 530-1700KHz for AM. You have to receive that carrier, remove that carrier and retrieve sound.

That retrieval is done by analog or digital processing.

Analog processing used variable caps and variable (tuned/preset) coils. Mixes some local generated frequencies which converts some intermediate form. That intermediate form contains that sound and further module does retrieval of that sound. All user interaction with knob is converted to mechanical movement and change in tuning devices within preset ranges. If physical mechanical (preset) state of these tuned devices changes then you get misalignment in any of the detection modules. Dust, rusting and displaced cores etc could do that misalignment.

Digital tuner works with the help of some microprocessor. It receives carrier, converts to intermediate format using tuned voltages controller by microprocessor. All user interaction is detected by microprocessor which changes various voltages and band, stations gets tuned. Now here sound detections is done by frequency division etc. There are no mechanically tuned devices. Still there are some filters and oscillators which are fixed callibrated. There are some reference voltages fixed and aligned. These may go out of alignment. Still these are very less in number as most of the parts are electronics devices and no changing of mechanical or physical state of tuning devices.

Forgive me, I avoided using words like superheterodyne, down conversion, modulation, demodulation and crystal clocks etc. That was done wilfully to avoid technical jargon.
 
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I vaguely remember this issue from childhood days. There were two small screws in the back of the gang condenser and also screw on top of IFT that needed adjustment, this was for my transistor radio.
 
I used to think that this was a simple error in the displayed frequency of the slider and the actual frequency

That happens in case of analog and acceptable if all offset is same even across the dial. I have analog receiver which is best tuned with 7mm offset between printed dial and pointer. But that is constant across both the ends of dial and needs fixing the pointer needle by moving it to correct place. I live with it because that is mechanically centred in the movement of the tuning range. If that is more at one end and less at other end of dial then it means stations are spread unevenly across dial and not according to dial. This is misalignment in tuner.

There is acceptable to have equal offset and spreading but expected uniformly within range of tuning dial.

Offffs... I explained spreading on the dial with the offset.
 
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Hi guys, Recently got a Nad 4020a tuner to pair with my Nad 3020. Being in chennai within 15kms of most broadcasts, I get a good reception just with the built in antenna.

But, the channels frequency is off by 0.3mhz, i.e., 98.3 is at 98.6, 101.4 at 101.6 and so on. Should I fix it or leave it as it is, as I already get good reception with built in although sometimes with slight distortion, which can be improved with better antenna. Maybe, it is important in a crowded fm space, but here we have only a dozen stations.

Is a trip to the service shop worth?


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