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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 10th Oct 2019, 5:46 pm   #41
19Seventy7
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Default Re: RRI T24E Chassis

Hi,

Sorry if this is a really stupid question, but what part is the tuning pin? Where do I contact the 2 pins to? I've never worked on tuners before, so don't really know the ins and outs of them. I've looked on the service manual but cannot distinguish the pin.

Would there be a way of getting it to tune into a locked frequency, bypassing the tuner almost? The converter I use allows me to choose frequencies to display using the whole UHF range.

Again, apologies for any silly questions.

Thank you for your help
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Old 11th Oct 2019, 12:52 pm   #42
Welsh Anorak
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Default Re: RRI T24E Chassis

They're reasonable questions.
As you have the manual, have a look at the diagram for the tuner. There will be a variable voltage pin, usually marked VT. Apart from this, there will be a +12V pin (possibly two), an AGC pin and earth. That's more or less it. You need to earth the negative prod of the meter to chassis and connect the other (+) to the pin you think is VT. If you don't know, the 12V pin will stay at 12V and the AGC will be around 5V. The tuning ppin will vary as you select another 'channel' (1-6) on the front of the TV. When you have this voltage, tune the selected button and you should see the voltage vary from less than a volt to around 30V.
If the selector is faulty - possible, but not all that likely - you could use a single variable resistor to put a voltage on the VT pin. However, since a tuner does just that, bypassing it isn't an option, and injecting video later on into a chassis of this type just isn't really a viable option when there are easier alternatives.
Let us know what happens.
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Old 13th Oct 2019, 9:41 pm   #43
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Default Re: RRI T24E Chassis

Hi,

Sorry for the late reply.

I'll get to doing that tomorrow. I'll let you know how I get on.

Thanks for your help
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Old 14th Oct 2019, 7:10 pm   #44
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Default Re: RRI T24E Chassis

For the life of me I cannot find VT on the service manual. I couldn't spend much time with it today either.

What would the tuning pin look like?

Sorry again if it's a stupid question

Thanks
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Old 15th Oct 2019, 12:31 am   #45
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Default Re: RRI T24E Chassis

Isn't that a T20 or Z718. Unless Rank used the same box throughout their range of sets.
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Old 15th Oct 2019, 8:32 am   #46
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Default Re: RRI T24E Chassis

I think they used the same box for a range of chassis and models. We have an identical looking Bush at the museum with the Toshiba C2290 chassis fitted. It has outstanding performance and has never had the back off, until I took it off since new. John.
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Old 15th Oct 2019, 2:28 pm   #47
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Default Re: RRI T24E Chassis

Yes - it's the same box on the T24. You could tell a Tv was fitted with the T24 because it had never had the back removed...
Back to your question. There are at the most five pins on the tuner. One will be earth, another +12V which only leaves a couple. Trace the wire back to the switchbank and you've got the tuning pin!
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Old 15th Oct 2019, 2:33 pm   #48
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Default Re: RRI T24E Chassis

Quote:
Originally Posted by Welsh Anorak View Post
Yes - it's the same box on the T24. You could tell a Tv was fitted with the T24 because it had never had the back removed...
Back to your question. There are at the most five pins on the tuner. One will be earth, another +12V which only leaves a couple. Trace the wire back to the switchbank and you've got the tuning pin!
Thank you for clearing that up! Ill get to do that ASAP.

Iíll let you know how it goes!

Thank you
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Old 15th Oct 2019, 9:41 pm   #49
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Default Re: RRI T24E Chassis

Wasn't the T24 Toshiba based? True, I never got one in for repair, saw thousands of T20\718 sets. I seem to remember the 718 even to went to schedule three and they were still unreliable. Did like the 18inch version though.
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Old 22nd Oct 2019, 1:00 pm   #50
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Default Re: RRI T24E Chassis

It was a Toshiba chassis in a Bush cabinet with a Rank tuner and front panel. Besides the 36k resistor in the chroma pulse feed, the chassis was no trouble.
However, the channel selectors, the tuner, the on-off switch all gave as much trouble asd they did on the T20 series, which is to say, quite a lot!
The Z718 you mention was another matter with its EHT overwind and stick. It was never going to work reliably on the large screen models, though, as you say, the 18" was nice and did give a very good picture.
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Old 22nd Oct 2019, 5:03 pm   #51
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Default Re: RRI T24E Chassis

Hi,

Really apologise but I've been investigating some more today, but I've really confused myself and cannot work out which board is the tuner.

I know this is a really basic part, but I've never had to work on a tuner section before, so haven't paid attention to that section of TVs, but what should I be looking out for? I thought it was the silver box connected to the aerial socket, but I think im wrong.

I can't find anything with several pins either

sorry for the basic questions again

Thanks
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Old 22nd Oct 2019, 5:23 pm   #52
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Default Re: RRI T24E Chassis

The tuner is the silver box, the pins are underneath it

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Old 22nd Oct 2019, 5:25 pm   #53
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Default Re: RRI T24E Chassis

You're right - that's the tuner. Look on the print side of the PCB it's mounted on and you'll see it has several pins leading from it. From those you should be able to work out which is which.
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Old 22nd Oct 2019, 6:28 pm   #54
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Default Re: RRI T24E Chassis

I thought it was, I must've been a bit braindead as I never thought to look on the printed side, which I always do.

I'll get to it ASAP.

Thanks
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Old 22nd Oct 2019, 8:58 pm   #55
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Default Re: RRI T24E Chassis

Hi,

Results come back, I either have a faulty tuner or a faulty DMM

With the negative pin earthed and testing each pin from the tuner I got a negative reading on each pin, all around - 0.002/0.005

Not sure what's happened there.

Thanks
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Old 24th Oct 2019, 12:55 pm   #56
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Default Re: RRI T24E Chassis

Er - I think you need to check your meter and its leads!
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Old 24th Oct 2019, 4:07 pm   #57
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Default Re: RRI T24E Chassis

Me too

It isn't the greatest DMM, as it was only cheap from online. The only thing I know that works properly is if it's testing for continuity!

I've never got a proper reading with it either, testing capacitors and such since either, testing it does actually work.

I think I'll need to invest in a better one

Thanks
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Old 24th Oct 2019, 4:16 pm   #58
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Default Re: RRI T24E Chassis

Photo of DMM might help to determine whatís going on - a picture better than a thousand words.......

Rgds
John
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Old 24th Oct 2019, 4:28 pm   #59
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Default Re: RRI T24E Chassis

After a screwdriver a reliable meter is an essential piece of kit. It needn't cost the earth either - I use a Fluke in the workshop, but I'm quite happy with the Chinese one I bought on-line for just over a tenner that I have in my tool box.
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Old 24th Oct 2019, 4:31 pm   #60
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Default Re: RRI T24E Chassis

I think mine was just under a fiver...

I wasn't expecting great things out of it anyway. They might possibly be the same as mine was online from China.

I'll get that photo ASAP, won't be right away as don't have the space at the moment.

Thanks
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