Help Needed - Thomson 27LCDB03B not working

[Acrantophis]

Yep, that will be the pin 1 indicator, different manufacturers will exercise different methods. What pad has lifted, if it breaks off when re-attaching the new device you will need to patch the circuit, which could be a ball ache. Not sure what to advise regarding the video issue though as I am a novice when it comes to TV repairs.

[micheldeman]

Hi,

I have managed to replace the U6301. I have checked all the pins and their connections to the first adjacent components and they seem to be fine. Soldering is an easier task then desoldering.
Meanwhile, I also replaced the 2 diodes D6303 and D6304 (I am now only left with 98 of these) and transistor Q6302.
Now I am trying to get hold of Q6301 a STW11NB80. RS components didn't have it in stock in their company shop although their website says they would. I am trying to get it through the person of ebay from which I bought the transistor and diodes.

Then next are the resistors.

Slowly but steady going...

Currently I have the power board of the other TV in my faulty TV. I have found that if I keep the TV on, also after it his been shut down, the green led still burns and I can see the back light is also still on, then after a few minutes or so, after I have switched on the satellite receiver, the TV continues playing (after a restart).
It is thus when the TV is cold, it shuts down, only after a while, when it is warm?, it keeps functioning. I found another thread that describes the same issue. http://www.fixya.com/support/t3580460-thomson_27lcdb03b_now_seems_need but no solution given unfortunately.

[Acrantophis]

So you've had some success with the replacing of the IC in that you didn't break any of the tracks. When I was researching the faulty PSU I had I discovered that whilst the manufacturer is kinown as Thomson within Europe, they also trade as RCA in America. So you might find the answers you seek by widening the search to include RCA LCD TV's.
From the symptoms you are describing I can't help but feel that the problem lies with a capacitor (Electrolytic type) this could even be one on the main board or inverter as opposed to the PSU card. You would need to visually inspect these to see if they are either bulging or burst, any that look suspect would be worth changing. I'll see if I can find anything further for you and will post it here, hopefully you'll be able to get it working soon.

[micheldeman]

I have replaced the STW12NK90Z (as alternative for the STW11NB80 or STW12NK80Z).
I tested/measured the resistor of 68K ohm, 2 watts. It seems to be fine. The 0.27 ohm 2 watts one is dead. I am trying to find it but it seems to be a difficult job. If anyone knows how/where to get it?
then I only need to find the smd resistors.

thanks,

Michel

[Acrantophis]

This is a 0.27ohms (0.27R) 3Watt device as opposed to the 2 Watt spec'd, provided it is the dimensional size it shouldn't be a problem, if anything it will be better as it can dispate more heat.

http://shop.conrad-uk.com/components/passive-components/resistors/smd-resistors/smd-resistors-rest-of/428874.html

[mattlumb]

I'm a bit late but, that's a wirewound resistor, Acrantophis.  It may work, but its internal inductance may be too high to accurately sense the fast-changing switching current.  The power supply may not be stable (whine/fizz) or may not regulate. A low inductance metal film resistor is the best choice.  I don't know the size of the original but a 2512 SMD resistor might be alright - this one is 0.3R and should do:
http://uk.farnell.com/bourns/crm2512-fx-r300elf/resistor-2512-0r300-1-2w/dp/1865266
Fitting a 3R in parallel would trim the resistance closer to spec. if needed.

Alternatively you can piggy back a 0.56R and a 0.51R (in parallel):
http://uk.farnell.com/bourns/crm2512-fx-r510elf/resistor-2512-0r510-1-2w/dp/1865267 and
http://uk.farnell.com/panasonic/erj1trqfr56u/resistor-2512-1w-1-0r56/dp/1717955

Matt

[micheldeman]

Sorry to interupt, the resistors of 68K and 0.27 ohm are conventional (through hole) ones.

The smd ones that I referred to, are other ones that I still need to find later on.

So I need a 2 watt 0.27 ohm conventional resistor.

You can see the one in question over here:
http://www.mijnalbum.nl/GroteFoto-KYJR7N7R.jpg
it's the green one.

thanks

Michael

[Acrantophis]

Matt, I was intentionally steering clear of Farnell due to minimum order values but it looks like the information I gave was bad anyway, so thanx for highlighting this.

Apologies Michael, I wrongly assumed that you were after a surface mount item, my bad, these might be a more suitable option http://www.ebay.co.uk/itm/10pcs-Ceramic-Cement-Power-Resistor-5W-0-27-ohm-/160575692046?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item25630e9d0e
As you advise the 68K device measured OK I've not looked for that.

Regarding the SMD resistors you are looking to replace at some point, if you can find the relevant section on the schematics it will tell you whether they are 0603 or 0805 devices, see NOTES at the bottom left of each section. Schematics here - http://www.tv.quuq.org/forum/index.php?action=dlattach;topic=5757.0;attach=2959 these should be easy to obtain from RS or other sources

[micheldeman]

Hi Acrantophis,

it's hard to find that 0.27 ohm 2 watt resistor. The link you gave directs to hong kong. Sounds strange that I have to go to the other side of the world to find a resistor. So I will keep that open for now and focus on the smd resistors first.

The ones are:
R6310 1206j10, I understood this means size 1206 and value 10ohm.
R6311 20k
R6327 1k
The sizes of these 2 I can't find on the schema, I only can see that they are a bit smaller than the R6310.
I checked an overview of smd sizes on the internet and I think they should be 0805 type.
Will go to RS in Nuneaton and see what they have.

BTW: the 2 watt resisitors are some kind of glued against the heat sink. It's some kind of compound but then hardened. How is this product called because I might need it later when I have to replace the 0.27 ohm 2 watt resistor? They probably need cooling.

Thanks again,

Michael

[micheldeman]

I came just back from RS components and bought the following smd resistors:

for the R6310 1206j10, I bought item number 6934502 (thin film)
for the R6311 20k, I bought item number 6791077 (thick film)
for the R6327 1k, I bought item number 2230427 (thick film)

As I don't know about differences beteen type of resistors, would these resistors be ok to use?

BTW, I found this link:
http://www.wiltsgrove.co.uk/product-details.php?catid=0027&subid=1104&itemid=FR-2051
No idea whether this resistor will do as replacement for the 0.27 ohm 2 watt resistor. Will try to contact them.


thanks,

Michael

[Acrantophis]

Quote:- BTW, I found this link:
http://www.wiltsgrove.co.uk/product-details.php?catid=0027&subid=1104&itemid=FR-2051

Be advised that this company also trades under another name but at the same address. Without knowing the component make up it would be difficult to say whether it would be OK or not. http://www.121spares.co.uk/contact-us.php

Just a thought, as you're only after the one resistor, have you any local TV repair shops? You could ask in store to see if they can source the component and sell it to you.

[micheldeman]

Hi, I have replaced all the parts. For the 2 watt resistor, I have put 2 others in parallel which gave me 0.25 Ohm. I tried the power board, but nothing, even the standby led didn't come on.
So I need to do some testing probably in the primary section of the board. I don't know whether I will be able to find it and whether it is worth it to continue investigating as I have spent already too much time on this thing. I see it more as just a challenge, but also that has its limits.

Keep you updated,

Michael

[micheldeman]

Last update,
I haven't tried to investifgate further on the powerboard.
What I have done however, is exchanged the video board from the 27" TV into the 30" one.
I thought already that this would be the problem for shutting down the TV. I noticed that when I switched the TV to 3:4 ratio, the TV didn't shut off as frequent as when I had it on 16:9 ratio. When the TV shutted down, the back light was still visible, so it couldn't be the inverter board, which wasn't compatible between the 2 TV's anyway. The 30" had more chips on the inverter board to cover the larger area to be lighted.
The 30" TV now doesn't shut down anymore and the 27" one plays currently on the video board of the 30" one. Probably the video board has become "weak" and could't power the larger screen anymore.