How to bypass 1 of the ccfl inverter output?

[jeremykum]

Hi,

I have this problem here, it's actually a laptop, HP DV9.
The screen has 2 ccfl backlight, and one of the tube is causing shortage.

This unit is using a dual output inverter, hence if I disconnect either 1 of the tube, it will auto shutoff. And the owner doesn't has the budget to replace the panel, and I don't want to take risk replacing the tube.

I had identified the faulty tube. Inverter confirmed working fine, tested powering with a spare tube pulled from another LCD.

If anyone here can guide me how can I modify the inverter so it won't shutdown even if I just connect 1 tube?

[Davi.p]

Re: How to bypass 1 of the ccfl inverter output?

You have to solder 1 resistor at the output with no lamp, tell us the model of the screen or its size.. i can't find hp dv9..
i refer to an LG 15,4" lcd datasheet:
Operating Voltage Unit
min typ max
VBL 670 690 810 VRMS
(6.5mA) (6.0mA) (3.5mA)
Operating Current
IBL 6.5 6.0 3.5 mARMS

Established Starting Voltage
at 25℃ Vs 1200 VRMS
at 0 ℃ 1560 VRMS

so you need i think a 1200/0,006=200kohm to 240kohm res. about 7W

[jeremykum]

Re: How to bypass 1 of the ccfl inverter output?

Thanks, it's a AUO B170PW04 v.0

You mean if base on your calculation, I need to solder a 240kohm at the output of the inverter.

You have to solder 1 resistor at the output with no lamp, tell us the model of the screen or its size.. i can't find hp dv9..
i refer to an LG 15,4" lcd datasheet:
Operating Voltage Unit
min typ max
VBL 670 690 810 VRMS
(6.5mA) (6.0mA) (3.5mA)
Operating Current
IBL 6.5 6.0 3.5 mARMS

Established Starting Voltage
at 25℃ Vs 1200 VRMS
at 0 ℃ 1560 VRMS

so you need i think a 1200/0,006=200kohm to 240kohm res. about 7W

[Davi.p]

Re: How to bypass 1 of the ccfl inverter output?

For your model is 1700/0,0065=260k

[jeremykum]

Re: How to bypass 1 of the ccfl inverter output?

For your model is 1700/0,0065=260k

Thanks ... will try tomorrow, need to go to stores to buy.

[budm]

Re: How to bypass 1 of the ccfl inverter output?

Do not forget about the dielectric voltage break down of the resistor, typical break down voltage is around 500V, to get 260K (that can handle 1200V) at 10W (instead of 7W for head room) will be hard to find, you should use at least 4 resistors (3W each) in series to handle the high voltage, and to dissipate the power will be difficult since you do not have much room on the panel assembly.

[Davi.p]

Re: How to bypass 1 of the ccfl inverter output?

Damn.. i forgot the huge heat.. mumble.. can you tell me the part no. of the IC on inverter, so i can see the voltage level for the feedback, maybe we can find somewhere the right point to connect to FB pin..