EEFL lamp interference on a Telefunken 32" model TLCD32FHDUA

[angelos]

Hi guys. This is a real head scratcher but perhaps someone has had this before. I have a 100x oscilloscope probe and measured the operating voltage is about 2400V. What should that voltage be? When starting up the tv initially its ok but over 30 seconds the image starts getting spklies and it gets worse over time. It even affects the tv next to me indicating a high level of EMI. It gets so bad that it affects the lvds signal causing communication problems with the panel. If i remove one lamp and start the set then the interference is 90% less. I can remove any lamp it does the same effect. Should i upload a video on youtube to show the effect?

[tom66]

Re: EEFL lamp interference on a Telefunken 32" model TLCD32FHDUA

I would check the blue caps around the HV output to see if they are arcing, you could try feeling them to see if they are warm (AFTER the set is switched off of course!)

[angelos]

Re: EEFL lamp interference on a Telefunken 32" model TLCD32FHDUA

How long should i let the set run before i switch off and feel? I let it run for 3 minutes and they all felt cool. Nothing funny.

[angelos]

Re: EEFL lamp interference on a Telefunken 32" model TLCD32FHDUA

With one lamp removed the peak to peak voltage goes up to 2400V and sparklies are reduced dramatically.

[angelos]

Re: EEFL lamp interference on a Telefunken 32" model TLCD32FHDUA

There was a lot of corrosion on the metal strips that hold the lamps in place. I removed them and acid treated the rust. It did help... Should i rather solder the lamps to the holders for better continuity?

[tom66]

Re: EEFL lamp interference on a Telefunken 32" model TLCD32FHDUA

Is the CCFL voltage stable?
The exact voltage can't be known unless you can find a datasheet for the lamps or LCD panel.

[angelos]

Re: EEFL lamp interference on a Telefunken 32" model TLCD32FHDUA

Hi guys. This one has been solved. The frame of the panel is made of plastic which means cheap and bad shielding. When i was struggling with the intermittent arcing i kept hearing a hissing sound in the middle of the eefl lamp which seemed wierd as it should not do that at that point. I decided to remove the lamps and stand offs and reflector plastic to see what is behind. Check photo attached, the one with those aluminium strips which are positioned directly behind each lamp. These are floating in the middle of nowhere (shielding) but upon closer inspection some of those strips were cracked right through and i assume the hissing was coming from there. I inserted a aluminium sheet covering all those strips then on the other side for good measure, check the other foto i also glued another aluminium sheet and presto..... no more arcing. . Anybody else had such an issue?

[tom66]

Re: EEFL lamp interference on a Telefunken 32" model TLCD32FHDUA

Interesting...heard of arcing but usually results in the brightness of the panel changing or the set shutting down with a fault.

[angelos]

Re: EEFL lamp interference on a Telefunken 32" model TLCD32FHDUA

This set has no modification done to its ccfl pwm ic to bypass protection but i can remove 2 lamps without it shutting down. All the lamps are connected in parallel.

[tom66]

Re: EEFL lamp interference on a Telefunken 32" model TLCD32FHDUA

Disabling the protection can lead to a fire, though, so be careful.

[arenat]

Re: EEFL lamp interference on a Telefunken 32" model TLCD32FHDUA

It´s a very well know issue around here . Last week I did one . A service bulletin say you must remove the alluminiun strips behind the tubes however shielding behind the boards even the t-con is enough .

[angelos]

Re: EEFL lamp interference on a Telefunken 32" model TLCD32FHDUA

It had me busy the whole day... not going to forget that one.