Removing RF tuner whatsits...

***2cvbloke*** · 27-06-2009

Just a thought...

With the switchover looming here in the Granada region (November), I was wondering what to do with my old TVs that have no AV facility, one being an old girly (pink accents and a heart tip on the aerial) Toshiba TV and the other being my old handheld Citizen CT555 (I think)...

Now, my thought is that an RF tuner thingy, at a guess (I'm no expert!!!

), converts the signal to an AV output, so, if I took out the tuner and replaced it with an AV input, then that would render the TV either capable of using a cheap-o brand freeview box, or useless (with my reverse engineering skills, it would most likely be the latter!!!)...

But of course, this is just my mind working overtime...

**HB13DISH** · 27-06-2009

Originally Posted by 2cvbloke

Just a thought...

With the switchover looming here in the Granada region (November), I was wondering what to do with my old TVs that have no AV facility, one being an old girly (pink accents and a heart tip on the aerial) Toshiba TV and the other being my old handheld Citizen CT555 (I think)...

Now, my thought is that an RF tuner thingy, at a guess (I'm no expert!!! ), converts the signal to an AV output, so, if I took out the tuner and replaced it with an AV input, then that would render the TV either capable of using a cheap-o brand freeview box, or useless (with my reverse engineering skills, it would most likely be the latter!!!)...

But of course, this is just my mind working overtime...

It will be the latter.
At least you have a working TV now, so why ruin it?
It would be easier to use an AV - RF Modulator converter than the other way round.
Have you checked if the the new system doesn't have an RF output, in addition to AV?

**rolfw** · 27-06-2009

Most UK Freeview boxes don't have built in RF modulators, only RF loopthroughs.

You can buy an RF Modulator for between £10 and £20, loads of them on Ebay

.

**Channel Hopper** · 27-06-2009

Save your money and use an old video recorder as the modulator. The tape mechanics of the box don't have to be working either.

Sky cunningly left out the AV loop from their boxes so they cannot be used for connecting anything else to the television.

***2cvbloke*** · 27-06-2009

The problem with the RF-AV modulators it that my Citizen handheld has no inputs for external peripherals, which is why I'm thinking of the modifications...

**HB13DISH** · 27-06-2009

Originally Posted by 2cvbloke

The problem with the RF-AV modulators it that my Citizen handheld has no inputs for external peripherals, which is why I'm thinking of the modifications...

But it does have an RF aerial socket, doesn't it?
If you have an RF modulated output, connect it to the aerial socket and tune the RF to the same frequency as the RF modulated. (VHF or UHF, depending on the source)
Try this with a VCR output or any other source.

***2cvbloke*** · 27-06-2009

Originally Posted by HB13DISH

But it does have an RF aerial socket, doesn't it?
If you have an RF modulated output, connect it to the aerial socket and tune the RF to the same frequency as the RF modulated. (VHF or UHF, depending on the source)
Try this with a VCR output or any other source.

It has no inputs, only a headphone socket and a DC supply socket, and of course the aerial itself...

In the past I have wrapped an RF cable's core round the aerial, and that seemed to work, but was fiddly to hold in place...

**PaulR** · 27-06-2009

It's one of those tiny TVs with a telescopic aerial isn't it?

You might be able to connect up proper coax lead by unscrewing the telescopic aerial and then, somehow, connecting just the centre wire from the coax.

If that works then you've proved the principle and investigate the RF modulator route.

***2cvbloke*** · 28-06-2009

Originally Posted by PaulR

It's one of those tiny TVs with a telescopic aerial isn't it?

You might be able to connect up proper coax lead by unscrewing the telescopic aerial and then, somehow, connecting just the centre wire from the coax.

If that works then you've proved the principle and investigate the RF modulator route.

I could do that, but, I'm thinking like someone on a narrowboat wanting to power a laptop, rather than going from DC to AC with an inverter, then AC to DC with a laptop PSU, use a DC-DC supply, removing the AC part, both saving energy and money...

So what I want to do is remove the RF element, so no AV-RF then RF-AV, just AV-AV, no need for a power source for the AV-RF adaptor, ontop of the power source needed for the TV and the AV device connected...

So, I'd like to just hoik out the RF tuner, and go right to the AV inputs...

(the bad dismemberment thing was a joke, I'm not that bad!!! I've had enough practise...

)

**Channel Hopper** · 28-06-2009

Problem is that the tuner may go through another set of amplifying stages before they are correct for the audio and video levels.

It might be worth looking for a schematic for the TV in serice manual (usually at your local library), or open the box up and look inside for test points, with an oscilloscope.

***2cvbloke*** · 28-06-2009

Originally Posted by Channel Hopper

Problem is that the tuner may go through another set of amplifying stages before they are correct for the audio and video levels.

It might be worth looking for a schematic for the TV in serice manual (usually at your local library), or open the box up and look inside for test points, with an oscilloscope.

Hmm, that's a good point, I'm not sure if my local library would have schematics for an old Toshiba TV (got to be early to mid 80s), but then, I haven't been to the library since I was pretty young, and I think they might have a hefty fine for not returning a book from way back then...

As for an o-scope, not got one unfortunately, though I do know how to turn a TV into a rudimentary one, though that's more for audio effects than for actually probing things...

**Channel Hopper** · 29-06-2009

Most of the libraries round here have a section for the manuals I used to use (television servicing).

And Ebay

throws up a few every now and then

320389213761

***2cvbloke*** · 29-06-2009

Originally Posted by Channel Hopper

Most of the libraries round here have a section for the manuals I used to use (television servicing).

And Ebay throws up a few every now and then

320389213761

That's a lot of schematics there!!! Why could they not make TVs all identical inside?

Don't think I'd have the money to buy that collection though, I only have about £10 to my name at the moment...

***pgh13*** · 29-06-2009

Just a few thoughts......

You could take a trip down to the reference library.....you may find collections of circuits there. Even if you can't find the exact model if you study a few you may spot trends which enable you to recognise where you'd need to input your signal to do what you want. The audio is probably easier to recognise but as sets have developed more is being done by fewer components so that may not be the case any longer. You may want to check out VCRs because they often had multiple inputs before it was common in TV and also they have nice low voltages to work with. Also, you need to remember that TV circuitry can be very cheap and nasty and live chassis used to be common practice - maybe less of a problem with portables

***2cvbloke*** · 02-07-2009

Completely forgot about this, but then I can't seem to find my handheld TV at the moment!!

But thinking ahead, if I were to work out how to get it all worked out and working, I was thinking of how to connect up AV things to the handheld...

Being a mono TV, it owuld be simple enough to get a 2-wire phono cable and a Stereo 3.5mm plug, wire it up with say audio on the middle ring and the video on the tip, with the ground being the outer ring, and do the same for a socket which I would fit inside the TV in place of the antenna, then solder it all into the TV, glue & screw, and try it out...

And an application for it has come to mind already, a mini "spy" camera (wired or wireless), wouldn't be much of a picture, but would be great anyway...

As for the little CRT portable, haven't had much thought on that, but, on the top, it has on the channel buttons the label "10/AV", which would lead me to assume that somewhere inside the TV there is circuitry for an AV input, just not utilised or lacking components, so all it would need is the necessary bits and maybe it'll just work, but I think that would need access to the TV repair bibles as mentioned!!!

**HB13DISH** · 02-07-2009

Originally Posted by 2cvbloke

Completely forgot about this, but then I can't seem to find my handheld TV at the moment!!

As for the little CRT portable, haven't had much thought on that, but, on the top, it has on the channel buttons the label "10/AV", which would lead me to assume that somewhere inside the TV there is circuitry for an AV input, just not utilised or lacking components, so all it would need is the necessary bits and maybe it'll just work, but I think that would need access to the TV repair bibles as mentioned!!!

Perhaps this means that program 10 is used for AV, in the old sense that VCR used to need a special channel in order to view the tapes better, and not necessarily means AV in the modern sense that it is used for audio / video with RCA or SCART connectors.

It would help if you take few pictures, with emphasis on the connectors.

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Removing RF tuner whatsits... For those who wish to discuss the more technical aspects of Satellite receivers and TVs. perhaps how to replace components, fault finding etc.

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