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Repurposing a analogue tv tuner can

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dr pepper

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I have a few tuner cans from parts mined tv's/vcr's.

I found some data on a couple of them, such as:
http://monitor.espec.ws/files/bd08rfp_232.pdf

I was wondering about the i2c command set for these, such as the above tu7601, I found the command set for a philps tuner and another non desript one, the commands llok the same.
I was wondering if the command sets are totally different or whether these things tend to be similar.
Just wondering if I could throw together a poor mans spectrum analyser with one of these, I know theres a project on the net for an analogue tuner, but not a i2c one.
 

Nigel Goodwin

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I considered such an idea many years ago, but at that time couldn't find any information on the I2C commands required.

The I2C actually goes to a PLL chip inside the tuner, but if you've got a datasheet for the tuner which gives the details that should make it pretty easy. Is it a combined tuner/IF or just a tuner?.

It's unlikely the datasheet for one tuner will work with another, as in sets that have different tuners fitted you have to change the software if you change the tuner.
 

dr pepper

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Thats the sort of information I was looking for.
So these things dont conform to a standard.
I tried one last night, the part number was only one digit out but it didnt work, looking at its datasheet even the pinout was different than the authors project.
Back to my mc1648 rf generator project then.
 

Nigel Goodwin

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My original idea was to use a tuner/IF assembly, simply scan up all the channels, and measure the signal strength using the AGC output from the IF - it wouldn't be fast (although it doesn't need to be), but it would be easy to do - if you could get the required details for the I2C data.
 

dr pepper

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That gives me an idea, I have a few tuners that are analogue, voltage tuned, a slow ramp would do the trick on those.
Might try that, the pic's a to d would convert the agc to digital, I'd just need a well filtered ramp signal.
 

Nigel Goodwin

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That gives me an idea, I have a few tuners that are analogue, voltage tuned, a slow ramp would do the trick on those.
Might try that, the pic's a to d would convert the agc to digital, I'd just need a well filtered ramp signal.
You could do it with the PWM output from the PIC, that's how the original circuits in the TV's worked - there was a 33V 'super zener' (ZTX33B) fed from a high voltage supply and resistor, with an NPN transistor directly across the zener. The transistor is turned ON and OFF by the PWM, giving a 33V pulse on it's collector - it was then fed via a simple two stage passive filter (resistor capacitor, resistor capacitor) directly to the tuning pin of the tuner.
 

dr pepper

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I have a couple with a taifun chip, there is 3 band i/ps, a tuning i/p, a agc o/p and IF out, 48mc I think.
One of the test circuits in the datasheet shows a pot on the tuning i/p and 3 switches for the bands.
It doesnt show the voltage at the top of the pot, are you saying it needs to be 30v or so?
I remember looking at a frequency standard project which got 20 bit pwm resolution from a pic, I still have the article and schematic, might be usefull for a hi res clean tuning voltage.
Might lash something up, generate a 1kc modulated signal and connect the If out to my Sdr through a attenuator.
The i2c one was more interesting as it had audio demod o/p's.
 

dr pepper

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Thats interesting and yes I've seen uhf varicaps operate at that voltage before.
Which gives me another idea, I found a site that explains how to use the same i2c tuner can as I have, but it doesnt use 30v, just 5v supply, I was thinking it'd have an inverter inside or something, but when I just checked the datasheet it does indeed have a 30v supply pin, and the schem for the telly says the pin has 30v unregulated, so theres probably a reg inside the can but not an inverter.
So I'll try and test it agian when I get home today, and this time with a 30v supply, I noticed that it received the 1kc tone if I tuned the rf gen to 150mc, which is probably the top end of band 1, which without 30v is probably all you'd get regardless of the tunign words.
 
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dr pepper

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Had another timewaste with the i2c tuner can before I give up with it, philips fq1216.
I verified I have i2c comms and the addresses are correct using an i2c scanner on the 'duino, it finds the tuner and the if ic ok.
However it doesnt appear to tune anything using some software I downloaded from github, and it specifies this model of tuner.
The tuners datasheet says there is a seperate power supply for both tuner and digital, but they are both 5v, theres a block on the block diagram in the datasheet that just shows 5v/30v so I assume thats a dc/dc circuit that makes 30v for the varicaps and mmics.
The donor for this was a telly, the one on github was a pc tv card, I wonder even though the p/n is the same whether theres some difference in the if or something, or its looking for an tv modulated carrier/subcarrier, I'm assuming it has a 10.7mc if/fm discriminator system as per the pc card one, might try wiring mi mp3 player to my sig gen.
 
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Nigel Goodwin

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If it's a tuner from a CRT TV, then it will almost certainly require a 33V super regulated supply - as that's trivial to arrange in a CRT set (just a ZTK33B and a resistor).

If it's out of something that doesn't have high voltage rails, then it 'may' possibly generate it inside using an inverter?.

I've just found a service manual for a Grundig STR1 analogue satellite receiver, and that uses a special 27V output winding on the PSU SM transformer to provide the tuner voltage - so not a UHF tuner, but exact same principle.
 

dr pepper

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Pulled from the datasheet:

The frontends have a built-in digital (I
2
C) PLL tuning system. A DC-DC converter circuit is built-in in the
FQ1216ME to synthesize the tuning voltage required, thus making the frontend a true 5V device.
Allthough the tuner can datasheet mentions FM, I think thats for the sound subcarrier on certain Tv modulation systems, Pal has an Fm sub, others this tuner is compatible with are Am.
So I dont think this tuner can receive Fm broadcast.
Another thing is the agc level o/p is analogue, its not available as a digital value.
Doesnt mean to say the can is useless, but theres no point trying to receive Fm broadcast on it, the only thing I'm going to be able to use is the agc o/p.
 
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Nigel Goodwin

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Pulled from the datasheet:



Allthough the tuner can datasheet mentions FM, I think thats for the sound subcarrier on certain Tv modulation systems, Pal has an Fm sub, others this tuner is compatible with are Am.
So I dont think this tuner can receive Fm broadcast.
It would be rare for a TV tuner/IF to be able to receive FM radio, the FM part (as you suggested) is for the inter-carrier sound - which was 6MHz in the UK, 5.5MHz in mainland Europe.

Another thing is the agc level o/p is analogue, its not available as a digital value.
Doesnt mean to say the can is useless, but theres no point trying to receive Fm broadcast on it, the only thing I'm going to be able to use is the agc o/p.
I presumed you were wanting a TV tuner?, if you want radio, then use a PLL tuner from an FM radio - or you could buy one of the cheap FM radio modules - something like this perhaps:

http://www.banggood.com/FM-Stereo-Radio-Module-RDA5807M-RRD-102V2_0-p-974260.html
 

dr pepper

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I have one of those, and the posh version that does RDS too, Havent read the 'sheet I presume it has a agc register.
I like the idea of the telly tuner as the range is low vhf to high uhf.
I might try looking for a tv tuner card for a pc, in fact I think I have one somewhere, that did tv/fm broadcast and had a can on the front end.
 

dr pepper

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Yes, thats true.
There is a narrow band mode in the If section, but I havent investigated that, narrowband tv signal wise could still be barn door width for a analyser.
Been interesting playing though.
 

Nigel Goodwin

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It'll be interesting to hear how you get on :D

I've just been studying the FM radio module I mentioned previously, looks a fun little device to play with - except I don't want an FM radio :p (but it's so cheap!!)
 

dr pepper

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I had a play with my FM modules like I was saying.
I had a tea5767, but with my ham fists and block of copper on a stick solder iron I ruined it, the Si4703 on the other hand works, some of the drivers for the arduino dont work well on RDS.
The signal strength meter has excellent resolution, however bandwidth is fairly wide at 75kc.
I'm going to put togther a marker generator and some software to plot a scan done with the Si4703 using the 'duino looking at the ic's signal strength meter on execl and see how it looks.
 

dr pepper

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I'dve expected a little wider as the max deviation in the Uk is 75kc, not sure what bandwidth a telly would be, however the finest visible video testbars on my old b&w 50's sets is around 400kc so I'd expect for a later colour set well over 5mc, colour burst as you know is 4.43mc.
Tuning time seems slow on the si, my car radio does the whole fm band in a few secs, but then I spose the search function changes its sensitivty on a repeat scan probably slowing it down.
This isnt really a serious project, just a mess around o the bench.
 
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