22nd Jul 2019, 10:51 pm | #1 |
Octode
Join Date: Jun 2018
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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. |
23rd Jul 2019, 8:42 am | #2 |
Octode
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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. Cheers Nick |
23rd Jul 2019, 9:08 am | #3 |
Dekatron
Join Date: Mar 2008
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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. Mark |
23rd Jul 2019, 9:15 am | #4 |
Heptode
Join Date: Jan 2006
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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. |
23rd Jul 2019, 1:39 pm | #5 |
Dekatron
Join Date: Apr 2005
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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. |
23rd Jul 2019, 3:56 pm | #6 |
Dekatron
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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.
DFWB |
23rd Jul 2019, 4:25 pm | #7 |
Dekatron
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Re: RRI T24E Chassis
I have a sheet for the T24F which is the same with remote control. Any good?
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23rd Jul 2019, 5:55 pm | #8 | ||||
Octode
Join Date: Jun 2018
Location: Essex, UK.
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Re: RRI T24E Chassis
Hi,
Thanks for the replies. Quote:
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 wouldn't've plugged it in if it hadn't been said to have been tested. Quote:
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:
Thank you all for your replies and help. I really appreciate it |
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23rd Jul 2019, 6:01 pm | #9 |
Dekatron
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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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23rd Jul 2019, 6:06 pm | #10 | |
Octode
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Re: RRI T24E Chassis
Quote:
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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23rd Jul 2019, 6:11 pm | #11 |
Dekatron
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Re: RRI T24E Chassis
I would have a look for any other stressed components before the big switch on.
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Frank |
23rd Jul 2019, 6:13 pm | #12 |
Octode
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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. |
23rd Jul 2019, 7:04 pm | #13 |
Octode
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Re: RRI T24E Chassis
I think I should add, no caps are bulging and nothing else looks to be damaged.
Thanks |
23rd Jul 2019, 10:17 pm | #14 |
Heptode
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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... |
23rd Jul 2019, 10:38 pm | #15 |
Octode
Join Date: Jun 2018
Location: Essex, UK.
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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 |
24th Jul 2019, 12:55 pm | #16 |
Dekatron
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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. |
24th Jul 2019, 2:21 pm | #17 |
Octode
Join Date: Jun 2018
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Re: RRI T24E Chassis
Hi,
I've sent you a PM Thank you for your help, I really do appreciate it! |
30th Sep 2019, 4:14 pm | #18 |
Octode
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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) |
30th Sep 2019, 9:44 pm | #19 |
Diode
Join Date: Aug 2019
Location: Sheffield, South Yorkshire, UK.
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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 |
1st Oct 2019, 9:00 am | #20 |
Nonode
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Re: RRI T24E Chassis
Some sound advice from the Rank experienced chaps here. Good luck with it.
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All the very best, Tas |