LCD 19" BENQ T905 problems

[chriz74]

Re: LCD 19" BENQ T905 problems

If the power LED is green or yellow, the power supply and logic card are likely to be working. That is, 1200AP40 is working.

Yes, led is alright but BENQ logo is not showing.

[icewolfca]

Re: LCD 19" BENQ T905 problems

I replaced the transistors and most caps. It now powers on and shows windows for about 1 second and then goes blank. What would cause it to work and then stop? Thank you.

[retiredcaps]

Re: LCD 19" BENQ T905 problems

What would cause it to work and then stop?

"2 seconds to black" is described in post #13 and #14 at

https://www.badcaps.net/forum/showthread.php?t=10419

Focus on

1) bad caps
2) bad inverter transformer
3) bad ccfl and/or wiring

Also, please post pictures of your boards as described in misc suggestions #1 in the same URL above.

PS. You MUST resolder all the inverter transformer pins on Benq boards.

PPS. Did you recheck the transistors to make sure they are not shorted after you installed them?

[icewolfca]

Re: LCD 19" BENQ T905 problems

"2 seconds to black" is described in post #13 and #14 at

https://www.badcaps.net/forum/showthread.php?t=10419

Focus on

1) bad caps
2) bad inverter transformer
3) bad ccfl and/or wiring

Also, please post pictures of your boards as described in misc suggestions #1 in the same URL above.

PS. You MUST resolder all the inverter transformer pins on Benq boards.

PPS. Did you recheck the transistors to make sure they are not shorted after you installed them?

1) I replaced most caps. After reading your post I replaced more caps. I need order some more.
2) I resolder the inverter transformers prior to posting here.
3) I sure hope not

but I did check my soldering job and there was a short or two and I fixed those. It now stays on and there are no issues any more. So it is all good . I am just starting and i lack proper tools. But I am getting there. Thank you for the quick reply and I LOVE this forum.

Josh

[chriz74]

Re: LCD 19" BENQ T905 problems

update:

I replaced all 5707 (4), 9024n (2) and the fuses. Lamps are still not working, led goes from orange to green when signal arrives from pc. I still can't see the BENQ logo.

[chriz74]

Re: LCD 19" BENQ T905 problems

.. well the NCP 1200ap40 is gone. It reads 300V on pin 8. Does anyone have a working one? It doesn't seem that easy to find.

[jannu47]

Re: LCD 19" BENQ T905 problems

Okay, has anyone following problem: First, the benQ logo shows about second or two, then blinks and, then shuts down the hole monitor. Fine, i have read all the messages on here, so i decided to replace the "bad" elite caps, all C5707´s, where half are burned, picofuse and re-solder all transformers.. And test.. Voila! We got a picture! :-) Also i read someone has got the picture, but about minute or two... So i decided to surf via net, use some youtube etc.. About one hour.. And we got the picture. So i assume that problem was fixed? Then i press the power button on the monitor and shut it down. Now, nothing came up, when i press pwr button.. Not even BenQ logo.. powerled stays green hole time, but no picture... Any quess, what goes wrong?

PS. Sorry about my bad english, hope that somebody can get a clue of this :-)

[alexanna]

Re: LCD 19" BENQ T905 problems

Check and see if the pico fuse has gone open

[jannu47]

Re: LCD 19" BENQ T905 problems

Thanx Alexanna for a quick response! Yeap, it was that! Picofuse has blown for first time and when i replaced it, the original fault came back.. A quick second or two benQ flash and then all black.. So it seems, that somehow the C5707´s burned again? Maybe those 9024N´s got to something to do with it? (I ask couple on resellers, but they don´t have them...) So i decided to use old ones... Well, they work (at once at least), because i got the picture once, only with new C5707´s...

[dantetrade]

Re: LCD 19" BENQ T905 problems

Hi, I got the same problem, my screen lit up for a few sec and went black. I followed the instructions: desolved/resolved transformers, K's,... Bought package on ebay (5.5£) of 4transistors C5707 + 2 Fets 9024n. Replaced these and ... screen works like new. My thanks to you all.
Important !!! Use the original transistors Sanyo 400 HFE. Replacements give only 200 HFE and just last for a sec.

[enoteco]

Re: LCD 19" BENQ T905 problems

Hi,
standard problem screen switch of after few sec,
following hints at post #21 and replacing C5707+9024n + picofuse;
now my my monitor work like a sharm .

Thank you all.

[^Active^]

Re: LCD 19" BENQ T905 problems

Hi I had the same problem so i decided to change one of the capacitors that was faulty. The monitor powered up normaly and i let it run for about an hour for a test. When i decided to shut it down by the power button it wasnt responding so i pulled out the power cord and now when i plug in the power the monitor doesnt work at all .. no green light no nothing . Any suggestions?

[selldoor]

Re: LCD 19" BENQ T905 problems

@active- Main suggestion would be to read this thread from beginning to end.
You will uncover the main problems. Start with easy things check the power cord and and fuse in plug (if you have fused plugs in Greece) check the cap you replaced.
Check the fuse/s on the board. Check the transistors. When you have done that come back and advise what you have found.

[^Active^]

Re: LCD 19" BENQ T905 problems

I have already done all these sorry forgot to mention it and i have read the forum also . Could it be the 1200ap40 that is causing the problem?

[jetadm123]

Re: LCD 19" BENQ T905 problems

I have already done all these sorry forgot to mention it and i have read the forum also . Could it be the 1200ap40 that is causing the problem?

Good focused photos of the top and bottom of YOUR power board will help members point things out for you to check. There were different variations of your power supply used in the T905 and without photos, it's difficult to provide help. Use the "manage attachments" option to attach your photos.

[jet]

Re: LCD 19" BENQ T905 problems

Hi All,

My first post here. Has anyone sourced an equivalent part to the FU9024N. I am in Canada and would like to find some local. Seems to me that part is week anyway. I read in another thread of someone modifying the circuit around the FU9012N but the link was dead. Any help appreciated.

Joe

[hua3]

Re: LCD 19" BENQ T905 problems

Hi 2 All,

I got the new parts (IRFU9024Ns) recently. So I mannaged to change one 9024N and pico fuse 3.A. Guess what! Monitor is up and running. I'll let it run for a while to see if the fix is permanent. So far it seems that IC 52 CJ5YK TL1451A is good. And I think it will be for some time

Thanks for reading and replying. I hope this thread will help to someone.

See ya

Hi all,

My LCD 19" BENQ T905 has the same problem: no power and no light of the power led. I checked that all the caps are ok (not blown), fuse is not broken, all the IRFU9024 have no any fried evidence. There is voltage on the 400 V cap when connect the power plug. Any one can help me to restart the monitor?

[selldoor]

Re: LCD 19" BENQ T905 problems

What voltage on the 400v cap?
Which fuse?
We need pictures
Welcome to the forum-
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

It will be useful if you can say what the supposed fault was and a bit about yourself - skills tools etc.

[hua3]

Re: LCD 19" BENQ T905 problems

Dear Selldoor,

Thanks for your quick reply. The voltage on the 400v cap c605 = 316V.
the 2 fuses measured on board are 0 ohm for f 601, and 0 ohm for the picofuse fp 601 respectively. I attached here the pictures of board both sides. Please help me to find the problem and give me instruction for resolving it.

[hua3]

Re: LCD 19" BENQ T905 problems

Dear Selldoor,

Thanks for your quick reply. The voltage on the 400v cap c605 = 316V.
the 2 fuses measured on board are 0 ohm for f 601, and 0 ohm for the picofuse fp 801 respectively. I attached here the pictures of board both sides. Please help me to find the problem and give me instruction for resolving it.