I have an E172FPB LCD that has a blinking green power button and a flashing display. I have disassembled the display and checked the boards for bad solder joints, burnt commponents. I couldn't find anything. There seems to be alot of postings with the same problem on the net. Would this be related to the inverter or the logic board? Anyone have any ideas for this BENQ produced LCD?

The first thing to check in this situation is the power supply.

Rich B

I checked the voltage going to the controller board. I compared it to voltages from a good working model. Where there should be 6.5v there is 3.3, 10.5 measured 5.6, where there should be 5.5v found none. Also the voltage fuctuates with the flashing of the lcd. The power inverter board is full of Lelon caps. None are buldging, but a know bad brand. Any suggestions?

Hi does this unit have the backlight inverter on the same PCB as the power supply.

If not then disconnect the backlight inverter and measure the voltage's again.

I have seen a lot with failed psu caps but this does not seem to be the case as you have 0V on one rail suggesting heavy over load.

Rich

Thanks for the help! Yes this is the integrated power-inverter board. This board fires two CCFL tubes. Spent alot of time researching this problem and trying to solve it. It's just personal now, gotta figure it out. I pulled some caps and tested, all were good. Even replaced a couple for kicks....still no go. I am happy to have narrowed it down to a power issue.

Hi that makes it a bit harder but usually there will be a fuse or link in the backlight inverter supply rail that you can remove to see if the rails come back up.

Problems with backlight inverters I have found are failed lamps, output fets/transistors and the output transformer, also check any capacitor across the primary of the transformers.

Rich B

Hi!

I do have the same problem and I found, the fault in my case.
On the board are there 4 transistor named q739,q740 for one tube and q759,q760 for the second tube one of this may be defect in my case it is defect. But I can't find any replace type maybe you known any ?
best regards
Jorgen Holst

Hi,

Thanks for the good tip. I've pulled two of the transistors quoted and one tested bad, one good. I'll pull the other two later, and post results. Richard B, what do you think? Transistors marked C5707 4c seem to be an oem from a quick search I did. Jim

Hi!
If you do find out which type of transistor can be use as a replacement type then let my now.
I did find firma in USA who sells those inverter board, but he don´t ship to Denmark.
Best regards
Jorgen Holst

Hi

If you need any of the transistors for the invertor board, please give me a call or send an email. i have 100pcs in stock.
tel +44 870 250 2037, fax +44 1803 850297
email componentspareparts@yahoo.co.uk

Would you please tell me where in the U.S. you found the board?

Thanks, Saroj

http://www.lcdrepair.us/kit-e172-e173fpb-inverter-power.html

THEY ALSO HAVE THE PARTS KIT YOU CAN BUY IF YOU WONT TO FIX IT YOUR SELF FOR $12.99

Hi again!

I have found som transistor for replacement of 2sc5707.
Sanyo says that 2sd1803 and 2sd1804 can be uset.
Best regards
Jorgen Holst

nte2524 is a good replacement and from eskc.com it is only $1.15 each
and from http://www.weisd.com/store2/ntesemi/NTE2524.html its $1.45 each still very cheap!!!

just thought this would help some of you out!!!

That nte number you gave is not right. The right part number is NTE2668 Hope this helps. Also you need to replace all 4 of them if not the ones that you did not replace will go down soon. Thought i would save you from haveing to take it apart another time!!

ON THE PREVIOUS FORRUM I WAS GIVEN A RADIO SHACK STOCK # FOR THE TRANSISTORS FOR THE DELL E172FPb POWER BUTTON FLASHING AND NO DISPLAY FIX. AFTER CONTACTING RADIO SHACK AND GOING TO THEIR ONLINE STORE I HAVE FOUND OUT THE STOCK # 348-4372 IS NOT IN EXISTANCE OR SO THEIR TELLING ME.THEN I TRIED NTE2668,... AND NOTHING AGAIN.THE PART DESCRIPTION I HAVE IS : NPN POWER TRANSISTOR D44H8,10AMP,60VOLT . THE ONLY THING REMOTELY CLOSE TO THAT TRANS, DESCRIPT. IS MODEL# TIP42G,CATALOG#276-2027,NPN TRANSISTOR,POWER DISSIPATION 65WATT, AND I(C)PEAK OF 10AMPS,6 AMPS CONTINUOUS.DOES ANYONE HAVE THE ABSOLUTE CORRECT 7 DIGIT PART#,MODEL#,CATALOG#,AND COMPLETE DETAILED DESCRIPTION OF THESE NPN TRANSISTORS SO I CAN FIX MY DELL FLAT SCREEN INSTEAD OF LOOKING AT THIS 15" HP BOX SMALL TV MONITOR TAKING UP MY WHOLE DESK PEICE OF GARBAGE.ANYONE...PLEASE HELP.IN DIRE NEED AS YOU CAN READ BY MY FRUSTRATION!!!!!!

Hi yes these are Sanyo 2SC5707.

http://service.semic.sanyo.co.jp/semi/ds_e/ENN6913A.pdf

Regards

Rich B

Just an update, three out of the four transistors were bad in mine. Still searching for replacement, will post when I locate some. Jim

Hi!

Read my Message above. There are an answere of the replacement type.
I got my monitor up running with 2pcs. 2sd1438 they get pretty warm so I put them on a cooling pad, but it's not the best way to do it but is running.
best regards
Jørgen Holst

REPLACE ALL 4 2SC5707'S AT THE SAME TIME IF YOU DONT YOU WILL HAVE PROBS

I have the same problem with blinking power but have not opened the monitor yet. Are all 4 of the transistors the same type or do they all have different part number?

Thanks

Did you get your Dell LCD fixed?

I just recieved this monitor...not sure I know how to fix.

I have a problem. When i turn on i can see the image for 1 second and then black image and the Led power blink on blink off.


Any idea? any hve the schematic for this monitor?
Regards

I fix it.
I changed a 2sc5707 and now the monitor is working.

Thank you

Pedro

I was having the same problem listed above. After looking at the transistors located at Q759, Q760, Q740 and Q739. Q760 was damaged (some of the plastic had melted off onto the board) I took them off, and replaced them with 4 2SC5707 transistor's from

http://www.bluestar-online.com/2SC5707_p/2sc5707.htm

After starting the monitor, I got some smoke and a pop. The transistor at Q760 was just as it was before i replaced it.

Any suggestions on what I did wrong?

Replacing the blown transistor/s is just the start.

Why did the transistor/s fail, it could have just be a transistor failure but for you this is not the case.

Output transformers are a regular failure in inverters as are the 150n caps across the primary where fitted.

Rich

Hi,
Does some one know what the Blue Cap values are if there is a need to replace some. C771 looks like it cooked and the meter showed that as a short. Moreover transistors Q750 and Q749 are cooked also.
Will changing the Interver board itself be the the best solution since work arounds dont seem to be that effective
regards

I am trying to find out where to actually find these parts.

I don't see Q759 on either of the two boards.

you installed them backwards

I should have searched more.

I started a new thread about this monitor.

Guess I just need to buy the monitor repair course..looks like it would be well worth it.

Hi you may have a different chassis in yours their are at least 2 chassis fitted to the E172.

E172FPb = BenQ

E172FPt = LiteOn

Rich

I have a Dell E173FPB made by Benq.

On the inverter board, T752 (same as T751) is burnt on the output pins.

The transformer is marked 19.26038.001 AND T0108A6210416 (with the latter number apparently being the most important).

Symptoms were that it would come on looking good for about 1 second, then the display would go off. Gren ligth stayed on solid.

Where can I order a an inverter output transformer ref # T752 for this?

They must be available, since there are folks (like Norris Parts) who rebuild them!

Thanks!

I have the same Dell monitor it to comes on at switch on for few seconds and then goes black. Did you find the problem with your's?

No that is not tranformer problem..

I have one of these monitors that suddenly went black screen I suspect it is a back light problem.
I know electronics having been in the industry for many years but I am no plastics expert.
Can someone please tell me the technique for opening the case on this model as there does not seem to be an easy way in and I would like to do as little damage as possible.
Thankyou in anticipation
Peter

"I have one of these monitors that suddenly went black screen I suspect it is a back light problem.
I know electronics having been in the industry for many years but I am no plastics expert.
Can someone please tell me the technique for opening the case on this model as there does not seem to be an easy way in and I would like to do as little damage as possible."

the answer is take the stand off then flip the monitor so that the plugs are facing up then look at the crack between the front and the back there are 4 indents in there so stick a flathead screwdriver in there and turn it should pop open then just go all the way around it doing the same thing

best regards,
Paul

I have the BenQ FP757-12 v.12 with similar symptoms... we've decided to replace the transistors.

Is there anything else to check?

Someone (elsewhere) mentioned replacing the parts FU9024 but we don't see anything labeled like this on the board.

The transformers don't look burned; the capacitors look o.k.; we only see one fuse near the main power unit; are there any other fuses that we should check or replace?

Thanks,
Saroj

THE OTHER FUSE IS MARKED PF751 IT IS AT THE TOP THE BIG 1000UF 400V CAP

Got a BENQ FP531 LCD which use exactly the same PCB with the same problem as described in this thread. Just replaced Q759, Q760, Q740 and Q739 with four 2sc5706 from local electronic store for NT$15 each (USD0.46) this afternoon and everything went ok. Thanks for all message contributors here, you guys are great!

Q760 shorted ..

change new but after power on q760 shorted again..

why..???

REPLACE ALL 4 2SC5707'S AT THE SAME TIME AND IT WORKED FOR ABOUT 5 MINS. NOW THE SCREEN FLICKERS WITH A BLANK SCREEN. I DID NOTICE THAT TWO OF THE CAPS ARE SOLLOWN (1,000Uf 10v). CAN SOMEONE PLEASE HELP.

I think ur problem is in the inverter section. check all c5706 transistors.good luck!