Re: Bad Benq 48.L1A02.A31 board for Hp1955L monitor

Hi,

I just wanted to inform you about my solution. The inverter died again and I could not find a reason for the new problem. It might be a pre-damage of the TL1451 from the first fault.
Totally pissed off, I de-soldered all the rubish from the inverter-side of the PCB and glued two small inverters (each 2 ccfl up to 400mm, price 5 USD...) on the free space.
Now it's as good as it was before. The automatic shutdown of the lamps has gone, but this is irrelevant for me anyway.

Congratulations...

Re: Bad Benq 48.L1A02.A31 board for Hp1955L monitor

No, this is not a 'small sizzling noise'. It sounds like an electric discharge (which it isn't..). It changes basic frequency with brightness settings of the monitor.
And the sound is only an indicator for the faulty PWM regulation. The other channel with the proper PWM is almost completely quiet.

Possibly, the reason for this irregular feedback/regulation of the TL1451 was the reason for the damaged SI4431 and 5707s too. I do not know whether the noise was there before the inverter died....

...

Re: Bad Benq 48.L1A02.A31 board for Hp1955L monitor

Hi,

first of all my appreciation for such a good forum which I found just by chance... :-))

I am trying to fix a HP 1955 Monitor. Symptom was a short flashing up of the CCFLs at power up and a strong smell.

One SI4431 was badly overheated (the one more close to the center of the PCB), in fact it burned a hole in the the black foil under the PCB.
One 2SC5707 was shortened.

I replaced the SI4431 and both 2SC5707 in this section.

Now, the inverter works...