Bad Benq 48.L1A02.A31 board for Hp1955L monitor

[toothsv]

I have a HP 1955L monitor, The Benq 48.L1A02.A31 board ruined, ¿how can I get a new one? where to buy it? Where do I look for it? or Is it needed to repair?

[ofcsilencer]

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

i recently had issues with this board too, but im no expert.

i couldn't just find a straight up replacement

when u say its ruined whats it doing? or failing to do?
do u have indicator lights?

[EGuevarae]

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

I have a HP 1955L monitor, The Benq 48.L1A02.A31 board ruined, ¿how can I get a new one? where to buy it? Where do I look for it? or Is it needed to repair?

Post problem & pics.

[ulihuber]

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 and lights all 4 CCFLs. But there is a sizzling noise coming from the area where the 2SC5707 have been replaced. I changed the 27p/3kV caps, the .22uF/160V cap. I resoldered the whole area but no change.

I started measuring with the scope and I can see a proper PWM on pin 9 of the TL1451 (which is the healthy second path). Pin 7 is somehow havily modulated/disturbed. Measuring on Pin 7 changes the frequency/charcteristic of the noise.

Anyone any idea of what it could be ?

Is there a proper schematic of the 48.L1A02.A31 board available ?
I know, it's close to the various other Benq boards, but matching component numbers would make it much easier.

Thanks
Uli

[Brian C]

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

small sizzling noise from CCFL inverter board is quite common...

[ulihuber]

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....

Uli

[toothsv]

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

There was an elevation of voltage from the electrical service, then the monitor started to blink and the image went off, then smoke from the back and a smell of plastic burned. I restarted the computer and the monitor gave image for a second and then went off again. Sent it to a bad tehcnitian, and the only hint he gave was shorted c5707. Changed 4 c5707 and two fqu11p06, tried again but still no picture. I upload the pictures, but it shows Q808 and Q809 with no original parts, those are parts that the first tech tried, but already changed to two c5707. The C824 is missing but was soldered back in place, not on the picture. Q815 and Q816 were replaced by two c5707. Q812 replaced by a new FQU11P06 same thing on the upper left side of the picture with a part with the big and raw piece of metal, replaced with a FQU11P06. Finally still no picture, just the power led on green

[toothsv]

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

Anyone with will to help can write to my email: heliodent@hotmail.com. I have high quality pictures of the board, but coul not upload them, because they are 4mb and this thing only permits 2.99mb

[toothsv]

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

better picture

[ulihuber]

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 to Benq - they managed to make it as complicated as possible while making severe design faults and giving it the least possible production quality. What a shame that HP uses such poor suppliers.


Greets
Uli

[EGuevarae]

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 to Benq - they managed to make it as complicated as possible while making severe design faults and giving it the least possible production quality. What a shame that HP uses such poor suppliers.


Greets
Uli

Pictures of the Franken-verter, please ...

[Pur_SSyn]

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

Thank you to the OP for starting this thread because I just had the EXACT
same thing happen to my HP 1955L monitor.

This seems to be a design issue without question; I wonder what the cause
of the failure might be?

Enjoy my photos even though this thread is a year old. Maybe it will help
someone else get through their trouble.

Circuit Board ID


Failure Area


My circuit board appear to be a different version from the orignal post,
however the IC is identical. Type the red text into a search engine to
download the complete data sheet.

Be careful when removing the damaged IC as the pads may lift from the
circuit board (mine did slightly). It's a single layer board so using flywires
to the component directly is not an issue.

Protective Insulator


mmm...smells good mixed in with burnt Fairchild

[tayart2004]

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

Hi everybody!
I have the same problem, I checked the transistors and i found that the Q815, Q816 are died and also the Q812 was shorted! I replaced the three parts and I still have the same problem no displaying on screen just a green light of the LED0...!!! I tried to see on the IC : TL1451A at the PWM output I have no signal and I measured on the pin 9 (+Vcc) and I found 0v...!!!??? so please if someone can help me to find out the solution.!
Thanks a lot

[PlainBill]

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

Hi everybody!
I have the same problem, I checked the transistors and i found that the Q815, Q816 are died and also the Q812 was shorted! I replaced the three parts and I still have the same problem no displaying on screen just a green light of the LED0...!!! I tried to see on the IC : TL1451A at the PWM output I have no signal and I measured on the pin 9 (+Vcc) and I found 0v...!!!??? so please if someone can help me to find out the solution.!
Thanks a lot

Note post #3. Top and bottom, please. See my signature for more information.

Did you resolder the transformers?

Did you check the fuse?

Again and again this is repeated. Repair advice is a case of Garbage In, Garbage Out. The more information you give us, the more (and better) assistance we can give you.

PlainBill

[retiredcaps]

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

I replaced the three parts and I still have the same problem no displaying on screen just a green light of the LED0...!!!

The "standard" procedure for Benq board is to

1) check the c5707s for shorts
2) check the fu9024 for shorts
3) check picofuse to see if it is open
4) resolder all the inverter transformer pins (mandatory)

[tayart2004]

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

Thanks a lot to everybody!

Finally I repaired my LCD!
I have changed the two transistors C5705 et the MOSFET J598 and the Picofuse PF701 and I soldred also HT transformers!
special thank to "Retiredcap"

[EGuevarae]

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

special thank to "Retiredcap"

"retiredcaps"

[tayart2004]

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

"retiredcaps"

Yes special thanks to RETIREDCAPS

[MHM1212SSS]

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

Thank you for all the valuable information