Fix for Benq FP737s 17" (Q7T3)

[enterthehatrix]

Re: Fix for Benq FP737s 17" (Q7T3)

Try these.

http://cgi.ebay.com.au/KIT-4-PCS-2SC...3286.m63.l1177

Thanks. That actually worked out cheaper than some I bought from another ebay seller (that haven't arrived still)

[Jacknewboy]

Re: Fix for Benq FP737s 17" (Q7T3)

Hello Davmax.

Thank you for your response. Yes I did solder all the transformer connections. Coincidentally, in the last couple of days, an old Kriesler television set (1976 - 59/3), that normally operates in my work area, has failed – the power supply has hiccups indicating an overload. I would bet on the failure being a faulty horizontal output transistor caused by cracks in the solder around the pins of the horizontal output transformer – probably caused by mechanical vibration. So not much is new!

Also, I must have been sleeping when I typed FET - I had the data sheets of the 2SC5707 bipolar transistors on the table beside me when I wrote the last note.

[enterthehatrix]

Re: Fix for Benq FP737s 17" (Q7T3)

Had no luck so far with replacing the fuse, FU9024N and 5705 , and I still haven't received those other 5705s I originally ordered.

Do you know what voltage the backlights take? I might try to power it externally as an alternative solution.


The bright side is that I can use these to make a multitouch screen.

[afo]

Re: Fix for Benq FP737s 17" (Q7T3)

hello all,

some very interesting reading, i like many others stumbled upon this thread when searching for a fix for the monitor i'm currently looking at. to be precise, a benq fp767-12 (Q7C3).

I've got a couple of hopefully easily answered questions and also some professional advice please...

The symptoms are that when connected the backlight flashes momentarily and a message in a small box in the middle of the screen also appears but it's too quick to make out what it's saying. The blue ring stays on and this action can be replicated by pressing the power button to off then on again.

On close inspection of the board, there seem to be no issues at all. No bulging caps, loose tracks..even the transformer joints look as good as the rest of them.

I used a multimeter on the 2SC5707's and got some form of reading over all 6 connections (BC, CB, BE, EB, CE, EC) - admittedly my knowledge of caps, trans and resistors isn't as good now as a few years back when I did Electronics GSCE haha.. but am i mistaken thinking i shouldn't have had readings from ALL polarities and pins? Or am i making an obvious error!?

Can someone confirm that this problem is most likely to be caused by the transistors/fuse/solder points? I know that may sound like a silly question on this thread, but i just wanted to ask seeing as there are a few different symptoms mentioned in the various posts.

the link provided by davmax to the US supplier on ebay will work out to be cheap so I will most likely try this out anyway. especially seeing as the owner of the monitor said if it's not a simple fix then to chuck it!

on to some advice...
having stripped the monitor and seeing that the screen itself is actually fairly slim, i thought of some more artistic uses for it if fixed. I was wondering whether it would be ok to mount the screen in some other form and then have the circuitry away from it? I would look into extending the two connectors for the backlights and can only see a problem with the ribbon cable...!?
the monitor has built-in speakers, which I wouldn't use...so i'd only use the power button mounted next to the rest of the circuitry.

thanks for reading!

[afo]

Re: Fix for Benq FP737s 17" (Q7T3)

not sure if anyone is even reading this, but i have now replaced the 6 components (3x 5707's, 2x9024's and 3A fuse) and re-soldered the transformer legs. I am happy to report the monitor is working fine...it's going back to it's former-owner rather than my plans for a designer piece lol...i have something else in mind now requiring a smaller lcd

thanks to the contributors of this thread who pointed me in the right direction from their work.

[PCBONEZ]

Re: Fix for Benq FP737s 17" (Q7T3)

Congrats!

[davmax]

Re: Fix for Benq FP737s 17" (Q7T3)

not sure if anyone is even reading this, but i have now replaced the 6 components (3x 5707's, 2x9024's and 3A fuse) and re-soldered the transformer legs. I am happy to report the monitor is working fine...it's going back to it's former-owner rather than my plans for a designer piece lol...i have something else in mind now requiring a smaller lcd

thanks to the contributors of this thread who pointed me in the right direction from their work.

Yes well done afo. Just read thread today. Your original meter reading description indicated transistor failure. Glad you fixed it so quickly with parts kit.

Extending the ribbon cable is not a great idea as you no doubt concluded.

[kopper]

Re: Fix for Benq FP737s 17" (Q7T3)

davmax, just want to say a big thanks for your input. I have a faulty 17" FP737s (QT73) monitor. I have a bit of experience and can fix most monitors myself, but this one had me stumped. I had replaced the transistors (Q739, Q740, Q759 and Q760) but still not working. Replaced IC751 and a few other sus parts, including most of the caps, but still not working. I was just about to give up and chuck this monitor when I thought I would have a search on the net.

I found the site, read your posts about the problem causing transistors and then read about the FUSE (PF751 on my board). Because it looks like any other capacitor on the board I completely overlooked it. I will have to get a fuse next week, but Im sure that Im going to have this LCD working again (thanks to yourself).

Just want to say thanks again. Your work is really impressive and I hope that one day Im as good a tech as yourself.

All the best to you and your family, you made my day!

[vinbar1]

Re: Fix for Benq FP737s 17" (Q7T3)

Hi everyone i am very new to this and My father-in-law is an electical enginare. He is teaching me some things. I was hoping someone had a skematic for this board so he can go more in depth with fixing this moniter. I have look everyplace I could on my own and came up short. Any help would be great.

When I first got the moniter it would power on but no back light. I could only see an image if it was plugged in to computer and at the right angle.

We so far have found that the bel 3a fuse is bad and 1 of the c5707s are bad.

Just to see what would happen we pulled the bad trannie and used a jumper for the fuse .

We were only able to get the Benq splash for about 2 sec and then it would go into standby. This is differant then what first was happening, as before the moniter would stay on just no back light and I never saw the benq logo. The only way to see anything was to have it plugged into the computer.

We are going to replace the trannie with a TIP3055 thats what i could find localy and I think we will just for now replace the bel fuse with a slow burn glass fuse and holder to see if that will realy solve the problem.

This is realy fun let me know what you think about what we are attempting and I will let everyone the results.

Thanks for this thread its awsome.

[Bobdee]

Re: Fix for Benq FP737s 17" (Q7T3)

Hello vinbar1
Much better to go with kit, heres a link,

http://cgi.ebay.co.uk/2SC5707-C5707-...3286.m63.l1177

there are many on ebay just search (2sc5707)
all the info you require to fix monitor is in this thread have a good read, pay paticular attention to bad solder joints on board especially the inverter transformers, Good Luck.
bob

[afo]

Re: Fix for Benq FP737s 17" (Q7T3)

hello all,

i received a call today from the friend whose monitor i fixed a little over a week ago - he gave me the news that after a couple of days usage it has stopped working again with the same problem!! i have said i would look at it again but i don't see much point in replacing the parts again if it's gonna blow again (!)...so i'm hoping for some more help from the experts...

is it likely that i need to put in the extended 'protection' mentioned in this thread, or does only a few days of usage imply other problems?! as previously mentioned, there were no bulging caps on the board at the time i did the first repair.

look forward to hearing back, Afo.

[vinbar1]

Re: Fix for Benq FP737s 17" (Q7T3)

Thanks Bob,

I am still intersted in the skematic so that I can learn more using this board as a teaching aid. I will get the kit after I test to see if what we fould was the problem.

Thanks again

[Bobdee]

Re: Fix for Benq FP737s 17" (Q7T3)

Hello again vinbar1
Did you see these they may help

https://www.badcaps.net/forum/showth...atic#post38917

https://www.badcaps.net/forum/showth...atic#post38612

https://www.badcaps.net/forum/showth...atic#post38239

the links they give may help you, if you have not seen them
. bob

[Bobdee]

Re: Fix for Benq FP737s 17" (Q7T3)

hello all,

i received a call today from the friend whose monitor i fixed a little over a week ago - he gave me the news that after a couple of days usage it has stopped working again with the same problem!! i have said i would look at it again but i don't see much point in replacing the parts again if it's gonna blow again (!)...so i'm hoping for some more help from the experts...

is it likely that i need to put in the extended 'protection' mentioned in this thread, or does only a few days of usage imply other problems?! as previously mentioned, there were no bulging caps on the board at the time i did the first repair.

look forward to hearing back, Afo.

Hell0 Afo


https://www.badcaps.net/forum/showpo...&postcount=141

https://www.badcaps.net/forum/showpo...&postcount=143

The aboye 2 links may help

The resoldering of inverter transformers seem to be your issue, it may take out a 2sc5070 again, also check whole board for cracks in solder joints some are hairline, use about 8 x magnification,I spend a good half hour or more looking, you will find some.
Good luck bob

[afo]

Re: Fix for Benq FP737s 17" (Q7T3)

Hell0 Afo


https://www.badcaps.net/forum/showpo...&postcount=141

https://www.badcaps.net/forum/showpo...&postcount=143

The aboye 2 links may help

The resoldering of inverter transformers seem to be your issue, it may take out a 2sc5070 again, also check whole board for cracks in solder joints some are hairline, use about 8 x magnification,I spend a good half hour or more looking, you will find some.
Good luck bob

thanks for your reply Bob, however if you look here:
https://www.badcaps.net/forum/showpo...&postcount=165

...you'll see that I did re-solder the joints but the problem has arisen again - hoping someone can comment on further possible causes.

thanks

[Wizard]

Re: Fix for Benq FP737s 17" (Q7T3)

UL-94V-0 is a tag that says the PCB substance met the inflammability that it snuffs out by itself when heat source is removed. Same for the components as well.

This is major reasons this prevented so much fires when a part or circuit board burns out.

I have seen results of burn craters (as in complete burnt through) in the circuit boards when this happens.

Cheers, Wizard

[Bobdee]

Re: Fix for Benq FP737s 17" (Q7T3)

Hello afo
Im sorry but your post I quote,

(not sure if anyone is even reading this, but i have now replaced the 6 components (3x 5707's, 2x9024's and 3A fuse) and re-soldered the transformer legs.)

says ONE transformer to me and does not mention the TWO inverter transformers, so there was misunderstanding, sorry about that
.. bob

[tanguy]

Re: Fix for Benq FP737s 17" (Q7T3)

davmax,

Thanks for your hard work in figuring out what's wrong with these BenQ LCD monitors! I followed the discussion in this thread and...

I just successfuly repaired a BenQ T701 a few minutes ago!

The hardest part was getting the bezel apart .

Thanks again, everyone!

[jtan]

Re: Fix for Benq FP737s 17" (Q7T3)

My HP 1955 has blinking problem, I wonder where I can get information on how to locate the fuse... Thanks!

[Bobdee]

Re: Fix for Benq FP737s 17" (Q7T3)

hello jtan
you do not say whether to buy, or find on board,if buy this may help

http://cgi.ebay.co.uk/LOT-OF-4-Bel-3...742.m153.l1262

seller also has 4A+5A fuses, good luck

also this thread would be better for you

https://www.badcaps.net/forum/showth...light=hp+l1955

bob