Broken CCFL in old 1992. Toshiba T6400DXC laptop. Unusual CCFL design. HELP!!!

[scokljat]

Hello all, long time no see :-)

Well, I'm a retro computer collector, and I like to make my computers functional and shine for museum exhibitions.

Here I have a nice Toshiba T6400DXC portable computer with a broken CCFL tube on LCD screen. LCD is SHARP LQ10D013 with two unusual large diameter CCFL tubes (see pic). Tube lenght is 264mm, and diameter is 12mm! Each tube has 4 terminals, two from each side of tube, 8 wires total for 2 CCFL tubes. One tube is broken, symptoms are as expected - backlite turns on for 1 second and then goes off.


My questions:

1. What kind of CCFL tube is that?? Why it has two terminals from each side?

2. Does this CCFL works like two standard CCFL's?

3. Can I use 2 standard 260mm x 2mm CCFL tubes instead broken one? How to wire it to existing four terminals??

4. What about using dummy resistor load to fool inverter and go with only one CCFL lamp? How to connect a resistor(s) to these four wires and what resistance and W to use because of this unusual CCFL design??


See detailed pics.


Thanks in advance!

Best regards,

Suad

[Th3_uN1Qu3]

Re: Broken CCFL in old 1992. Toshiba T6400DXC laptop. Unusual CCFL design. HELP!!!

That's actually a regular fluorescent tube, the kind you put in your lighting fixture. It has 4 terminals because it's got filaments to warm up the gas before striking, while modern CCFLs used in screen backlights, do not.

[scokljat]

Re: Broken CCFL in old 1992. Toshiba T6400DXC laptop. Unusual CCFL design. HELP!!!

That's actually a regular fluorescent tube, the kind you put in your lighting fixture. It has 4 terminals because it's got filaments to warm up the gas before striking, while modern CCFLs used in screen backlights, do not.

Thaks for quick reply! So what is your suggestion?

Thanks,

S

[Th3_uN1Qu3]

Re: Broken CCFL in old 1992. Toshiba T6400DXC laptop. Unusual CCFL design. HELP!!!

Depending on the design, it may or may not strike a modern CCFL, but feel free to try. The inverter won't be damaged. Use only one red and one white wire, doesn't matter which ones, but match the colors to the CCFL wires. See if it at least attempts to strike the lamp.

[scokljat]

Re: Broken CCFL in old 1992. Toshiba T6400DXC laptop. Unusual CCFL design. HELP!!!

Depending on the design, it may or may not strike a modern CCFL, but feel free to try. The inverter won't be damaged. Use only one red and one white wire, doesn't matter which ones, but match the colors to the CCFL wires. See if it at least attempts to strike the lamp.

Thanks, I will try.

Do you suggest I put two standard CCFL's each to one red/white wire pair? That could be a problem because there is no resistance between reds or whites because there is no resistance from heater wire so inverter could shut down.

What about standard T4 6W florescent tube?? Do you think it could be direct replacement for original one?

Thanks,

S

[budm]

Re: Broken CCFL in old 1992. Toshiba T6400DXC laptop. Unusual CCFL design. HELP!!!

"That could be a problem because there is no resistance between reds or whites" So the two White wire are not tied (connected together) at the circuit board? Same for the Red wires? You may be able to use T4. How long is the lamp any way. I do not believe the circuit can produce high enough striking voltage (1200~1500V) to start and running the voltage (700~1000V) for the CCFL lamp.

[scokljat]

Re: Broken CCFL in old 1992. Toshiba T6400DXC laptop. Unusual CCFL design. HELP!!!

"That could be a problem because there is no resistance between reds or whites" So the two White wire are not tied (connected together) at the circuit board? Same for the Red wires? You may be able to use T4.

No, they are not. Do you want me to take detailed picture of inverter connector and PCB traces for you?

Thank you for your help.

S

[budm]

Re: Broken CCFL in old 1992. Toshiba T6400DXC laptop. Unusual CCFL design. HELP!!!

I believe the T4, T5 lamp may work. I do not know the dimension of your original lamps.
https://www.bulbtronics.com/Search-T...ookieSupport=1

[scokljat]

Re: Broken CCFL in old 1992. Toshiba T6400DXC laptop. Unusual CCFL design. HELP!!!

I believe the T4, T5 lamp may work. I do not know the dimension of your original lamps.
https://www.bulbtronics.com/Search-T...ookieSupport=1

OK. So T4 flourescent tube 230mm x 12mm "cool white" will be my first try. Original tube length is 264mm. I'll connect two red wires to one side and two white wires to other side. ...and hope for the best ;-) Btw, I'm quite uncomfortable with hi voltages. It gives me creeps.

http://www.lyco.co.uk/aurora-6w-t4-f...ool-white.html

One thing puzzles me, T4 lamp works at 220VAC, so this laptop inverter has output of 220VAC?! If it's true, standard CCFL's would not work at all?

S

[budm]

Re: Broken CCFL in old 1992. Toshiba T6400DXC laptop. Unusual CCFL design. HELP!!!

The board looks like it has step up transformer (running at high frequency) and the circuits to light up the filaments to start the lamp. CCFL (Cold Cathode) uses high voltage to strike up the lamp, no filament.
http://en.wikipedia.org/wiki/Fluorescent_lamp

[scokljat]

Re: Broken CCFL in old 1992. Toshiba T6400DXC laptop. Unusual CCFL design. HELP!!!

The board looks like it has step up transformer (running at high frequency) and the circuits to light up the filaments to start the lamp. CCFL (Cold Cathode) uses high voltage to strike up the lamp, no filament.
http://en.wikipedia.org/wiki/Fluorescent_lamp

Well OK, I got a T5 6W 220mm x 16mm lamp bought in local shop. I'll try it tomorrow. If it works I can buy T4 6W 232mm x 12mm from ebay as there is no T4 in local shops.

Huh, is there any possibility the lamp will explode or something?! I'm quite uncomfortable with hi voltages and mercury content inside...

What is the worst that can happen? ;-)

Cheers!

S

[scokljat]

Re: Broken CCFL in old 1992. Toshiba T6400DXC laptop. Unusual CCFL design. HELP!!!

Success!! Installed T5 6W 220mm cool white fluorescent tube. It works. It's shorter than original tube, it's little dimmer and warmer color. Inverter works OK.

The worst that can happen is the screen has little warmer colors at lower part of screen. ..first I have to recap LCD electronics as most of caps has visibly leaked.

Can it be any better? Well, if I buy T4 lamp 232mm 6W daylight it could be better match for original tube...

Will get beck to you when recap the screen and put all back together.

Thanks for your help!

Cheers,

Suad

[budm]

Re: Broken CCFL in old 1992. Toshiba T6400DXC laptop. Unusual CCFL design. HELP!!!

Glad to hear, the day light white may look better.