Baird X42DTV 42" LCD fixed PSU, but low brightness

[baddesley]

Hi guys, I have just got this set working after a long period. Originally all I got was a flashing/strobing on the screen, with the 12V rail low. Eventually afer a lot of time searching for posts on this and lots of new caps, replacing C31 (100uf 25v), the set powered up OK.

However, although the set works, the picture is rather dark, even with the brightness set to maximum. Is there any internal adjustment which woud affect this, or a factory reset? I have looked, but can't find this or any info on it anywhere. Any help on this would be much appreciated, thanks.

[baddesley]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

Anybody got any ideas, or a circut diagram?

[budm]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

Do you know if the dimming control is analog or PWM type? Does the TV have auto-dimmig control by sensing the room lights?

[baddesley]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

Hi Budm, thanks for the suggestions. Unfortunately, I don't know, as I haven't been able to find any useful information on this set.

Anybody got a service manual or any other info on this set?

[selldoor]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

There have been threads where sets (not baird iirc)were dim due to a failed voltage regulator on the main board. Perhaps pictures of your boards would help.

[budm]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

If you can get the LCD panel make and model numbers then you can look up the spec sheet which will tell you the pinout of the inverter board so you can check the Dimming control lines.

[baddesley]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

Thanks guys, I'll have a look at that and post a picure of the main board later this evening.

[baddesley]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

Ok, I've had a look, but I couldn't see any Make/Model nos. for the screen. The only numbers I can see on the main panel without taking it all apart are these, which are presumeably the chassis numbers: DC0UZ0E0700, H67AL0169. Nothing came up when I did a search for either of these. Presumably the screen numbers are 'burried' under the main chassis.

I have uploaded a photo of the main chassis boards, don't know if this will be of any help though.

[Neelix]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

Not all the boards appear in the photo. Take some more photos so that we can see all the boards

[baddesley]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

That is all the main boards, there's only the two inverters (far left and right), which I know are working Ok and the HD board, which is burried under the metalwork just above what's in the photo.

[budm]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

If we can see the connectors on the inverter board then it may have label for the pins to tell us which one is the Dimming control line.

[baddesley]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

OK, here is the LHS Inverter board and connections (best photo I could get with my old camera). I have replaced the two 470uf electrolytic caps, as they were bulging (slightly bigger/higher voltage fitted). The board LED comes on when it starts up and the backlight can be seen through the top and bottom chassis gaps (see second photo), as it does on the other side.

[selldoor]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

Did you also replace the caps on the slave inverter board? and what make/series did you use

[baddesley]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

Yes, I did. I always replace caps like this in 'sets' where there are several in a particular circuit(s). The ones I used are marked 'Hitano'. They are low ESR 105 degree caps. The original ones were all bulging on top. The ones I used on the PSU are all the same spec, but various makes, chosen for the best suitability depending on capacity, value and physical size. They all seem to work well.

The TV starts and runs fine, it's just the low brightness level that is a problem. It looks OK on some 'light' outside scenes (with brightness on max. and coontrast around 45%), but inside scenes are rather dark. All inputs are the same (except the HDMI input, which strangely 'disables' the brightness, contrast and colour adjustments and results in a dark over-coloured picture!).

Maybe it's just the age of the screen or backlight, is that possible? Without a service manual or circuit diagram, neither of which seem to be available, I just don't know what to check. It's a shame, because it's not too bad a picture when it's bright enough (though nowhere near up to modern standards), but is unwatchable a lot of the time and therefore, basically scrap as it is!

[selldoor]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

Anything on those main board connectors to suggest a DIM pin that could be traced?

[selldoor]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

Had my thinking hat on - if the number on the inverter is to match to the panel so perhaps
some info here to assist budm ( I dont know what it all means )

[budm]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

Check pin 11 and pin 13 while making the backlights level adjustment.
Notes: most TV will have backlights level adjustment and brightness adjustment which are not the same.

[baddesley]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

Thanks guys, those document could be a great help! It's going to take me a while to work my way through all that info and check it out, but I'll let you know how I get on. Cheers!

[baddesley]

Re: Baird X42DTV 42" LCD fixed PSU, but low brightness

Thanks everyone, the LCD document was very good, it was for the exact type of LCD and Inverters in my set. Unfortunately, I was still not been able to get to the bottom of this, as the control voltages seemed to be normal (though there was a range given, so not absolutely sure). I tried varying the non-varying control line by tying it up/down to the 12V/0V line, but this had little effect. Also, I could not find any backlight adjustment anywhere in the menus or physically. I have now given up on this and have sold it to someone who is going to use it as a games monitor. Thanks again for the help!