Yamaha tuner board mods and hacks

Thread Starter

Robmack1975

Joined May 18, 2020
7
I would like to understand how this am fm tuner card works. Specifically how the audio from received stations is output on the connections. How would you change the band and frequencies? This is just a hobby so any technical info would be much appreciated. I guess my goal would be to be able to change the band and frequency, attach a frequency counter as a display.
 

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Audioguru again

Joined Oct 21, 2019
1,931
You change the band with a switch and you change frequencies with a 2-gang variable capacitor.
It would be very difficult to add a frequency display.
 

bertus

Joined Apr 5, 2008
20,773
Hello,

When adding a frequency display to a receiver, you can take the oscillator signal and add or subtract the MF frequency, depending on the system.

Bertus
 

MisterBill2

Joined Jan 23, 2018
7,040
I would like to understand how this am fm tuner card works. Specifically how the audio from received stations is output on the connections. How would you change the band and frequencies? This is just a hobby so any technical info would be much appreciated. I guess my goal would be to be able to change the band and frequency, attach a frequency counter as a display.
Without a clear complete picture of the circuit board there is no reason for any to attempt to guess about the question.
 

MisterBill2

Joined Jan 23, 2018
7,040
To effectively change the frequency range that would be received by this receiver is not simple. The resonant frequency of each of the RF tuned circuits would need to be changed by changing both the inductance of the coils and the capacitance of the capacitors. IN addition, the resonant frequency of the local oscillator would need to be changed in a similar manner. And if you had to ask this question you need to study and understand the circuit before any of those changes can be considered.
AND, one more thing is that almost all radio frequency signals outside of the range of this tuner are not nearly as strong, so it would also need to be adjusted to provide more signal gain.
 

Thread Starter

Robmack1975

Joined May 18, 2020
7
Here are some photos of xs283 Yamaha tuning card. I just would like to know how to change the frequency as if the original switches were controlled to the white connector
 

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Thread Starter

Robmack1975

Joined May 18, 2020
7
I applied 12 volts to board. I used my oscilloscope and proved around and the only thing that looked interesting was the crystal showed a typical wavelength on the scope. I tried probing around on the connectors while it was powered up and really didn’t see much with the scope. I’m guessing the board that controlled this FM tuner card would’ve had its own circuitry with the correct voltages to control this board would that be a fair assumption?
 

MisterBill2

Joined Jan 23, 2018
7,040
The circuit board in the pictures is an AM/FM receiver board. Changing from the AM section, (550 KHZ to 1650 KHz) to the FM section (87Mhz to 109MHz) is not re-tuning the receiver frequency, it is selecting two different circuits with different components. Selecting a different frequency range is every bit as complex as I described in my previous post. It is certainly not as simple as giving the board an instruction to operate at a different frequency. I would be reluctant to attempt such a change with a circuit board that complex and closely packed even if I had a circuit diagram of the board. And you will need a circuit diagram to see what would be involved.
 

Thread Starter

Robmack1975

Joined May 18, 2020
7
Does anyone know where the audio output would be. I’m talking about the unamplified audio signal that’s output out of this card.
 

Thread Starter

Robmack1975

Joined May 18, 2020
7
This is really a waste of your valuable time. For a good time get an SDR

https://blog.bliley.com/10-popular-software-defined-radios-sdr
I’m not trying to receive frequency out of band. Just trying to get an understanding of how the board works. I’m sure most of the Japanese models with this type of Board are functionally similar. I have ham radios for listening and taking. Maybe I should get a more fundamental base knowledge on combined AM/FM
 

MisterBill2

Joined Jan 23, 2018
7,040
The circuit board in the photo has three ICs visible. Those devices have model numbers, and from that you will be able to locate the manufacturers data sheets and application information. Especially the application information and the associated circuit descriptions will provide you with the means to understand what happens in each device. That will certainly help you understand how the system works.
And now a guess, based on experience: That shielded metal enclosure towards the edge of the circuit board probably includes all of the FM high frequency section, the RF amplifier, the local oscillator for the FM broadcast band, the associated mixer circuit, and possibly an IF stage. In some brands and models it may even contain the entire FM receive section, although that is less common.
 
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