Broken CRT

total_ass · 27-07-2007, 7:15 PM

My family's living room TV recently broke a couple days ago so they have given that to me in the chance that it can be repaired and bought their own HDTV.

The tv is a 32 inch widescreen Bush CRT. I don't really want to throw it away as its a very nice tv and my bedroom is only a 4:3 21 inch :P

Anyway onto the problem. The tv apparently didn't turn on one day and started making a small burning smell. The fuse in the plug has been checked so the problem is in the actual tv.

When turning the tv on next to a speaker, a popping sound occurs meaning an emf is being given off. I don't know if this helps but i thought it might be worth mentioning. There is no power light but the popping sound occurs every few seconds when the switch is on. It's almost as if the tv is trying to turn on but can't.

I have no experience with tv's but i can get into it fairly easy and i am a reasonably skilled solderer, so if it is a single component that has burnt and needs desoldering and replacing then i am probably capable of it. Obviously if the CRT has fully burnt out then i'm guessing it can't be fixed.

What would you lot recommend as the next course of action for this? If it came down to taking it to a repair shop then how much would i be looking at cost wise?

Thanks in advance for any help you can give.

Andy98765 · 27-07-2007, 7:27 PM

My father in law just had his CRT TV repaired, £110, without saying it I thought that was a waste of money, Asda are selling Big old CRT's for just a tiny bit more.

total_ass · 27-07-2007, 7:34 PM

I wouldn't need to buy a new one really as i am happy with my 21 inch it would just be nicer to have a bigger screen that is widescreen. It would depend how much it cost to get repaired if it came down to that.

I'm going to university in like 2 months and can't really lug a huge CRT with me anyway so it's kind of repair this or chuck it. I have a 22 inch DVI monitor that i play xbox 360 on and just use the TV for watching videos on my xbox 1.

I would probably go up to £50 for a repair but that is clearly not going to happen and would probably cost close to or more than what your father in law paid.

JayCee · 27-07-2007, 7:54 PM

Quote:

Originally Posted by total_ass

What would you lot recommend as the next course of action for this?

Your "next course of action" is to report back with the full model no taken from the rear label.

total_ass · 27-07-2007, 8:09 PM

Yes sir!

BOX76NBLK

JayCee · 27-07-2007, 11:07 PM

Quote:

Originally Posted by total_ass

Yes sir!

BOX76NBLK

That model uses the Beko 14.2 chassis...there are so many possibilities for
the "tripping" noise and burning smell that I would suggest you do not have a go at repairing it yourself...it could be something reasonably inexpensive like a short circuit capacitor which inc labour would cost probably around £40-£50...at the other end of the scale it could be a faulty line output transformer which would be a lot more expensive...you would really need to get an experienced engineer to take a look and give an estimate.

total_ass · 28-07-2007, 10:34 AM

Thanks for the replies.

Is it worth me cracking it open and taking a look at all?

total_ass · 29-07-2007, 3:41 PM

Got bored and had nothing to do so i took it apart.

Couldn't find anything wrong with it and then i decided to turn it on and this component was smoking.

JayCee · 29-07-2007, 4:11 PM

If it's the chopper transformer that's smoking there is a short-circuit somewhere...you need to get it looked at by a professional.

total_ass · 29-07-2007, 4:34 PM

can the transformer itself not just be replaced?

thanks a lot for your posts.

martytoo · 29-07-2007, 6:49 PM

The Transformer may not be faulty, if as pointed out elsewhere there is a short circuit somewhere on the output side of the transformer this would cause the transformer to overheat and smoke!
Go to your Local reference library and see if they have back issues of Television Magazine and/or any TV Fault Finding books. I forget the exact details but there was an excellent series of books which published full circuit diagrams for TV's etc. If they've got them have a good search through them you might just find the answer to your problem.
Bear in mind however there are some seriously high voltages floating around TV sets so mind where you put your fingers!

JayCee · 29-07-2007, 7:08 PM

Quote:

Originally Posted by total_ass

can the transformer itself not just be replaced?

Are you absolutely sure that is where the smoke is coming from.
At the bottom of your pic I can see what looks like two blue-coloured high voltage ceramic capacitors...these often go short-circuit and produce a burning smell and smoke...whereas unusual for a chopper transformer to smoke...not unheard of but not that common.

total_ass · 29-07-2007, 7:49 PM

Ah it is indeed possible.

The tv is positioned so the board is vertical so those capacitors are underneath the transformer and it may very well be the smoke from those rising up, i'll have another look tomorrow.

It is difficult to tell because i can't get the board off of the case so i have to look at it from a funny angle but ill move the crt out.

If it is just these particular capacitors then i assume that they can be fairly easily replaced but can they be purchased easily?

Thanks for the help.

JayCee · 29-07-2007, 10:37 PM

Quote:

Originally Posted by total_ass

If it is just these particular capacitors then i assume that they can be fairly easily replaced but can they be purchased easily?

Yes easily available.
I doubt the two of them have gone...if one has went s/c it will be split or have a blackened tear across its face.

total_ass · 29-07-2007, 10:53 PM

Thanks, i'll be looking in more detail tomorrow morning/afternoon.

I can't seem to remove the mainboard out of the case? Is this at all possible? There are tiny clips preventing its direct removal but even with those pulled out of the way it seems stuck to the case?

JayCee · 29-07-2007, 11:09 PM

Quote:

Originally Posted by total_ass

I can't seem to remove the mainboard out of the case? Is this at all possible? There are tiny clips preventing its direct removal but even with those pulled out of the way it seems stuck to the case?

There are usually 2 maybe 3 small chrome-coloured Philips head screws securing the pcb to the plastic chassis frame.

total_ass · 30-07-2007, 8:25 PM

Thanks for the help i have identified it was actually a tiny green capacitor next to the big blue one. This was smoking quite vividly and has a crack down the side of it almost as if it has burst.

I'll desolder it tomorrow and have a look in maplins or something for a replacement. If it turns out that the writing on it is unrecognisable due to burns then is there anyway of identifying the specific one i need? Is there a circuit diagram for this model i can have a look at? If you can help a bit more it would be really appreciated

JayCee · 30-07-2007, 8:40 PM

Quote:

Originally Posted by total_ass

If it turns out that the writing on it is unrecognisable due to burns then is there anyway of identifying the specific one i need?

Yes, give me the circuit reference no printed alongside it on the pcb.

total_ass · 30-07-2007, 9:08 PM

C619 dude

Thanks a lot.

JayCee · 30-07-2007, 9:24 PM

Quote:

Originally Posted by total_ass

C619

C619 is a 470pf 2kv high voltage disc ceramic capacitor...it will be marked on its body as "471"...easily available at Maplins or anywhere else that sells electronic components...I'm pretty sure that's all you'll find wrong with it...these are cheaply made caps and often go short-circuit.
Good luck.

total_ass · 30-07-2007, 9:29 PM

Thank you very much friend. You have been extremely helpful in this matter. Whilst checking my pm's from a couple years ago (i dont come on here much) i noticed it was indeed you who helped me a couple of years ago with a tv that had an overstretched 60hz picture.

You are a credit to this forum and you have my gratitude.

I am in the process of desoldering it as we speak. I had to desolder two wires that were going from the mainboard onto a couple of silver clips that were stuck to a silver strip wrapped around the crt, i'm guessing this is normal as i couldn't find any other way of detaching them.

I'll let you know how i get on with this, thanks again.

JayCee · 30-07-2007, 9:40 PM

Quote:

Originally Posted by total_ass

Thank you very much friend. You have been extremely helpful in this matter. Whilst checking my pm's from a couple years ago (i dont come on here much) i noticed it was indeed you who helped me a couple of years ago with a tv that had an overstretched 60hz picture.

You are a credit to this forum and you have my gratitude.

Quote:

Originally Posted by total_ass

I had to desolder two wires that were going from the mainboard onto a couple of silver clips that were stuck to a silver strip wrapped around the crt, i'm guessing this is normal as i couldn't find any other way of detaching them.

Correct, that's the only way...those are earthing straps from the crt "aquadag"...don't forget to resolder them when you've finished and before switching the set on.

total_ass · 30-07-2007, 9:59 PM

Capacitor came out without a hitch. Will post the end result tomorrow afternoon.

Thanks again, you've possibly helped me save a tv here which would otherwise have been thrown out (can't really afford repair fees being an unemployed pre-university student

).

You're in the repair business right? Aren't you losing customers by helping people out for free on here?

JayCee · 31-07-2007, 9:33 AM

Quote:

Originally Posted by total_ass

You're in the repair business right?:

Yes, 40 odd years, the last 8yrs self-employed and getting poorer every year due to cheap imported crap.

Quote:

Originally Posted by total_ass

Aren't you losing customers by helping people out for free on here?

If I thought you lived near me I would have talked you in to me repairing it for a small fee

But as you don't I wouldn't like to see a perfectly good set getting tossed for the sake of a 50p component.

total_ass · 31-07-2007, 4:45 PM

Well the very unhelpful people in Maplins in Birmingham said they didnt have a 471 marked capacitor , or a 470pf capacitor that was 2kv.

They had one that was 100v but thats it. they were quite unhelpful.

Are there any other stores you can think of that would sell this? I can order online, that isn't an issue.

Chris Muriel · 31-07-2007, 5:17 PM

CPC/Farnell : http://cpc.farnell.com/jsp/search/br...?N=411+1000031

Chris Muriel, Manchester

total_ass · 31-07-2007, 5:34 PM

thanks for the link mate it has been favourited!

I'm guessing a 470pF would work where a 450 is required?

For example, either one of these would work?
http://cpc.farnell.com/jsp/search/br...questid=338160

Thanks again AVForums!

JayCee · 31-07-2007, 7:32 PM

Quote:

Originally Posted by total_ass

thanks for the link mate it has been favourited!

I'm guessing a 470pF would work where a 450 is required?

For example, either one of these would work?
http://cpc.farnell.com/jsp/search/br...questid=338160

Thanks again AVForums!

Either of those would be okay...it's a 470pf.

total_ass · 31-07-2007, 10:47 PM

Yeah sorry i misread it, i'm very tired lol.

As if the people in Maplins said you couldn't get 470pF with 2kv. Lol dumbasses.

Will order now and post one last time with the final verdict!

total_ass · 05-08-2007, 12:14 AM

Works great! Thanks for the help!