Repairing TFT TV (flat chance ..) ;-(

[T i m]

Hi All,

A lady friend bought a 400 quid TFT TV for the bedroom a while ago (~1yr?, probably against my advice at the time) and recently the picture died (but still sound / channel controls etc though).

Yesterday she phoned threatning to dump it on me 'because you can fix anything' and I managed to put her off (had it been completely dead it *might* have been a fuse or summat but as it had sound ..)?

She had tried to contact the supplier but they have since gone and apparently the manufacturer wants 'silly money' even to have a look at it, with repair guesstimates of around 200 quid ( near the current new price of such items)?

So, I wondered if there was any 'proven / reaonable' repairer of such things any one here may of used, or, if there are any real chances of a d-i-y repair (for an electronics eng of sorts)? I suggested that even if I was able to locate a faulty componed there was a good chance

*I* wouldn't be able to get one as a spare .. ?

And 'I know', there may be high voltages on the backlight inverters and/or the SM PSU but I promise I will wear rubber .... (and not just whilst working on the TV either probably ..) ;-)

All the best ..

T i m

[Andy]

You are on a bit of a hiding to nothing here. In order to troubleshoot a TV you really need the technical manual, detailing voltages and waveforms. Also you might benefit from some spare components to plug in and try. Accordingly you really need at least a multimeter and oscilloscope, plus high-voltage probes. Also on the web there is a commercial website detailing the preferred failure mode database of lots of TV's, but it is a pay-site, if not a professional subscription site.

In summary, to take the back of the TV and poke around carries very little chance of success. If you want to do it, bear in mind there'll possibly be a bleeding great capacitor with 300V on it sat charged up on the pcb ( this may be different with flat screen tv's but don't count on it ). The only thing you can do without at the least a circuit diagram is look for toasted components, or ( with a bright light and a magnifying glass ) bad solder joints - they sometimes develop a circumferential crack which goes high impedance.

Central libraries often carry TV circuit diagrams, though they may not carry the one you want. Again, without good test equipment and the possibility of testing by substitution, that will only improve your chances a little.

Worth a look on the offchance something fairly simple has gone wrong ( look at connectors as well ) but don't waste a lot of time on it. One for the professionals I think.

Andy.

[Grunff]

It's a TFT. The highest voltage will be 200-300V powering the backlights.

[Dan Mills]

Silly thought, but the backlights are functioning? That would give no (or a very dim) picture with sound!

Regards, Dan.

[Grouch]

Shine a torch on it; if you see a faint picture, it's the back-light inverter. Getting the thing out is another story, that's why they charge so much for the repairs.

[gg1000]

I wouldn't even consider this repair.

TFT sets have very few "reparable" components and what there is that can be fixed would need technical manuals and/or a stack of working spares to try out.

My experience of places that do fixed-price repairs of these sort of things is that they replace entire units (PSU, display, main PCB etc.) and bin the non-functional bits. They don't bother to repair any of the major items - it's just not worth the time. Enough of the units need very simple repairs (new PSU etc.) that they make up for the few that take the most expensive components (probably in this case the main display).

If you don't know how they work, and don't have the diagrams or at least a stack of spares, then you are likely to be fiddling for hours or days with only a relatively small chance of fixing it.

[Colin Wilson]

How did she pay ? - I wonder if she might have a case against a credit=20 card issuer as the goods were not of durable quality.

12 months on a =A3400 TV is hardly what i`d call a reasonable lifespan.

--=20 Please add the word "newsgroup" in the subject line of personal emails

**** My email address includes "ngspamtrap" and "@btinternet.com" ****

[Mike Dodd]

Normally I'd agree, but in this specific case I reckon it's worthwhile investigating the back-light - as mentioned earlier in the thread.

If the invertor has gone, or there's a single tube (unlikely) and that's gone then this should be a reasonably straight forward repair.

If, however, the backlight is fine then repair is unlikely.

Mike

[Mark S.]

As said - sounds like it's possibly the back light tube(s) - try turning the contrast and brightness up full and see if you can make out the picture.

You can buy the tubes but having seen and handled them they are extremely fragile and very easy to break.

Mark S.

[T i m]

Thanks to all for the replies folks .. lots of good sense as usual ;-)

I do still have some tools (DMM, HF Scope, HF FC) but as mentioned, probably not much in the way of spares (short of various molex connectors possibly) but probably less chance of a diagram as it's quite 'new' (I mean, for TTF TV's in general .. unlike yer old Ferguson chassis l).

I'lll get her to do the torch backlight test .. costs nothing and might tell us something.

If it were mine I might at least take the back / bottom off and look for burnt connectors (remember P8/9 PC AT power connectors burning in the early days?) broken wires (at connector crimps)/ PCB cracks, dry joints around the bigger pins / connectors etc but I hold little hope. I'm not sure of the history of this TV .. I think it was bought, stood on a wall bracket and from there untouched .. (ie. not moved about a lot?).

I did ask her to text me the model details but nothing as yet ...?

I like the idea of her exploring the matter via her credit card .. I know some PC TFT carry 3yr warantees?

All the best and thanks for your time again ..

T i m

>

[T i m]

FWIW she just sent me the following ..

Samsung 15 inch

Model code LW15M13CX/XEU Model LW15M13C. S Type No MU15EO

.. via her 'BlackBerry Wireless Handheld' (apparently) .. this girl loves her gadgets .. drives an Alpha 33 as well .. ;-)

T i m

[Alan]

..........Then she can affort to buy a new one instead of trying to get you to fix it on the cheap!

Alan.

[zikkimalambo]

When she does, name them and shame them here!

Also, if you enquire in sci.electronics.repair giving those details, they may come up with a common fault and fix for that system.

[s--p--o--n--i--x]

flat sceens have a shorter lifespan than CRTs

[Derek ^]

Some of the projection TV's have a lamp, the replacement of which is a £200++ item and have a service life of 2,000 Hrs.

Telly on 12 hrs/day, life expectancy =167 days = 5.5 months !

Actually I had assumed the OP was talking about a thin TFT TV. But there's nothing in the post to say so.

Tim, the bulb's not gone has it?

[Ian_m]

Not quite, most panels blank the LCD if their is no tube power. Been there done that, couldn't see a thing with the inverter disconnected. Connect inverter supply 380V but disconnect tubes and you can see a faint pciture. Oh the voltage only majorly tingles when touched, not recommended but you will survive.

[John Laird]

Near-ish. Someone was offering a 17" TFT with tuner for about that, over the bank holiday weekend.

I can't offer any advice beyond what you've already had, but would suggest next time your friend seriously considers buying at John Lewis. They offer a free 5-year guarantee on TVs. (Yes, they will be slightly above net prices, but not by anywhere near the cost of the additional warranty.) I don't think I'd accept the usual 12-month guarantee on technology which is still fairly new, and/or on items which can't be economically repaired.

[T i m]

You are right but I'll try not to be clever with the subject in future ;-(

"Repairing TFT TV (flat chance ..)"

All the best ..

T i m

[T i m]

Well, that was one of my background thoughts but she has been a good mate (ex workmate) ;-)

All the best ..

T i m

[T i m]

;-)

Thanks for the heads up on that one.

All the best ..

T i m