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Old 22nd Jul 2019, 10:51 pm   #1
19Seventy7
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Default RRI T24E Chassis

Hi,

I picked up a 1980s TV a few weeks ago which uses the T24E chassis. It was described as tested but not working. I picked it up and brought it home for a project. Being told it was "tested" I plugged the TV in (I wouldn't have done so if it was said to be untested) and spent the next 5 minutes figuring how to turn it on - turns out the volume dial needs to be pulled out. The set turns on, and the screen produces a nice bright raster. "It wor-" BANG
I unplug the set and notice smoke coming from the back, so open up the windows to cool it down.

I let the set cool down and after 10 or so minutes I turn the TV round and open up the back. I did a quick visual inspection, all capacitors seem to be intact, albeit it leaky. And I noticed it had been in a damp environment.

After a while I realised that a transformer has blown. (I think mains, as the mains lead is connected directly to it)

Some of you might've seen, but I've put a "Wanted" post up for a service manual/schematics/diagram for the T24E chassis. I've had a look around online, but I keep being shown to a LG flat screen…

I wonder if anyone knows what value the transformer is, as it'll need replacing.

Thank you

Last edited by 19Seventy7; 22nd Jul 2019 at 11:02 pm.
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Old 23rd Jul 2019, 8:42 am   #2
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Default Re: T24e Chassis

I think we need some more information. What is a T24e? Who is the set made by? Photographs of the chassis and especially the part you think has failed.

Transformers don't go bang when they fail, but they can produce lots of smoke!
What makes you think it has failed?

In my experience repairing TV's, it's actually quite unusual for faulty components to look faulty! They usually look perfectly OK and need to be found by proper fault diagnosis & voltage measurements whilst referring to the circuit diagram.

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Old 23rd Jul 2019, 9:08 am   #3
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Default Re: T24e Chassis

I agree, more likely to be a mains suppression cap or possibly the main smoother.
It is never a good idea to power up an unknown set before removing the back to inspect the chassis.

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Old 23rd Jul 2019, 9:15 am   #4
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Default Re: T24e Chassis

T24E sounds like one of the chassis from the Rank-Toshiba days.

This thread is about a Bush set and the T24E chassis is mentioned in post 4.
https://vintage-radio.net/forum/showthread.php?t=24329

As Nick says, a logical approach is called for. You might be lucky and find that it's the mains filter capacitor that has failed.
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Old 23rd Jul 2019, 1:39 pm   #5
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Default Re: T24e Chassis

It will be a Bush T24 with Toshiba innards. A bang is certainly very unusual in this set as is a transformer failure - the only faults I remember are the tuner and the 36k pulse feed reistor to the decoder IC.
I must have a manual - PM me if you need it.
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Old 23rd Jul 2019, 3:56 pm   #6
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Default Re: RRI T24E Chassis

The Rank T24 is a development of the Toshiba X53 chassis. There might still be in the filing cabinets RRI service manuals for the T24 series.

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Old 23rd Jul 2019, 4:25 pm   #7
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Default Re: RRI T24E Chassis

I have a sheet for the T24F which is the same with remote control. Any good?
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Old 23rd Jul 2019, 5:55 pm   #8
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Default Re: RRI T24E Chassis

Hi,

Thanks for the replies.
Quote:
Who is the set made by? Photographs of the chassis and especially the part you think has failed.

Transformers don't go bang when they fail, but they can produce lots of smoke!
What makes you think it has failed?
I'm not sure who the set is made by, as it's branded Co-Op so i'd guess it's been rebranded. (I have seen other TVs with the same cabinet before but not branded co-op but I don't know which it is for sure - I've attached a photo incase it could help)

I've attached a photo of the transformer, and as you can see it looks (And smells) burnt. I think the black bit should've been covered in plastic, as there is some yellow plastic remaining on the side, and I have a small piece which matches the plastic.

I read online that older transformers can explode when the insulating materials age and start absorbing moisture.


Quote:
I agree, more likely to be a mains suppression cap or possibly the main smoother.
It is never a good idea to power up an unknown set before removing the back to inspect the chassis.
I'll get to testing ASAP and fingers crossed it is just a capacitor that's failed.

I wouldn't've plugged it in if it hadn't been said to have been tested.

Quote:
It will be a Bush T24 with Toshiba innards. A bang is certainly very unusual in this set as is a transformer failure - the only faults I remember are the tuner and the 36k pulse feed resistor to the decoder IC.
I must have a manual - PM me if you need it.

I hope it's not a transformer failure, I don't know if anything else could be faulty as it hasn't been turned on since the bang and smoke. I did wonder if it'd be okay after a while if moisture (if it was a wet transformer fault) was dried out and the set turned back on. Of course I haven't yet, I want to be sure beforehand.

Quote:
I have a sheet for the T24F which is the same with remote control. Any good?
If you could send it over I'd really appreciate that. It'd be a good start as I have nothing so far.


Thank you all for your replies and help. I really appreciate it
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Old 23rd Jul 2019, 6:01 pm   #9
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Default Re: RRI T24E Chassis

It has C813 written at the side of it, I think that is a Rifa capacitor. Not cost much to replace it, very likely work without it while you test the rest of the set.
It will be across the mains input, see post #3
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Old 23rd Jul 2019, 6:06 pm   #10
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Default Re: RRI T24E Chassis

Quote:
Originally Posted by Nuvistor View Post
It has C813 written at the side of it, I think that is a Rifa capacitor. Not cost much to replace it, very likely work without it while you test the rest of the set.
It will be across the mains input, see post #3
I think you might be right. I just got myself very confused as the shell of the capacitor had blown open, and was then touching the transformer, which made me think it was connected.

Oops!

So it should be safe to remove and turn the set back on without it for now?

Thanks for your help!
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Old 23rd Jul 2019, 6:11 pm   #11
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Default Re: RRI T24E Chassis

I would have a look for any other stressed components before the big switch on.
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Old 23rd Jul 2019, 6:13 pm   #12
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Default Re: RRI T24E Chassis

There are a couple leaky caps, but that's all I can see.

It did switch on for a second when I turned it on originally so might get a result. The set wouldn't be on for long anyway, just a little while to see if it turns on still and if there's a full raster etc.

Thanks

Last edited by 19Seventy7; 23rd Jul 2019 at 6:23 pm.
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Old 23rd Jul 2019, 7:04 pm   #13
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Default Re: RRI T24E Chassis

I think I should add, no caps are bulging and nothing else looks to be damaged.

Thanks
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Old 23rd Jul 2019, 10:17 pm   #14
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Default Re: RRI T24E Chassis

These Rifas tend to go bang. Have a check if there are more of them in the set and replace them. Many sets only have one Rifa, and that is the one that gave you the surprise. If there are no more Rifas just remove the stinker and try again. (With caution of course)

I have an old Tandberg set from the 60's which is full of these caps. It has been stored in a damp garage and all the Rifas have cracked due to absorbing the moisture. Not looking foreward to replacing them...
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Old 23rd Jul 2019, 10:38 pm   #15
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Default Re: RRI T24E Chassis

Hi,

It was just the one. I've since turned the set on and it seems to be okay. It needs some work but so far it seems good, doesn't look to be any major issues.

Thanks
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Old 24th Jul 2019, 12:55 pm   #16
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Default Re: RRI T24E Chassis

There aren't likely to be many problems as they were good reliable sets.
Bush did badge these Co-Op along with the T20 and T22 sets. The Co-Op used to rent out Bush dual standard mono sets badged Defiant with slightly different cabinets.
I'll send you the manual when I have your address. I'll mark the 36k resistor you need to replace as it'll soon give trouble if it isn't already. It's an odd value, so you might need to make it out of a couple of components. 1W survives better.
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Old 24th Jul 2019, 2:21 pm   #17
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Default Re: RRI T24E Chassis

Hi,

I've sent you a PM

Thank you for your help, I really do appreciate it!
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Old 30th Sep 2019, 4:14 pm   #18
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Default Re: RRI T24E Chassis

Hi,

Got quite stuck with the TV.

I’ve been trying to sort the issue for some time now.

The screen is a green/grey colour, and goes solid with a video input and tuned in. The sound is fine.

I’ve replaced a few caps which hasn’t made any difference. I’ve also replaced the 36k resistor with a 1 Watt variant as Welsh Anorak suggested.

I’ve attached two photos showing the only results i get on screen.

The first shows no input, the second shows it tuned in.

(Are the heaters glowing too bright? They’re very bright even under normal room lighting)
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Old 30th Sep 2019, 9:44 pm   #19
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Default Re: RRI T24E Chassis

Hi

Those crt heaters do look rather bright, they are usually fed from a winding on the l.o.p.t.x via a low value resistor or small coil which has an impedance at line frequency and sometimes engineers short them out to boost a low emission crt.

I have no experience of your chassis but that arrangement is very common to a lot of sets of that era.

Might be worth checking if that has been done to the crt heater supply.

Harry
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Old 1st Oct 2019, 9:00 am   #20
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Default Re: RRI T24E Chassis

Some sound advice from the Rank experienced chaps here. Good luck with it.
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