Shorted HP L1955

[vbripple]

Re: Shorted HP L1955

Krankshaft... ".22 uf at 160 volts?"

yea on the BENQ sit between the 5707 pairs. I'm assuming to stablize and absorb heat.

only way it could be called one stop shopping is if you used just one computer to hunt everything across the net.

[jesco_d]

Re: Shorted HP L1955

hi im new here and im also have the same problem with the hp l1955 monitor. dark screen. I'm learning a little bit of electronics and one of those transistors 5707 was shorted and a secondary fuse was open. I found a transistor in my stuff but the numbers were differant than the 5707 I just put one and the numbers was c3904. then I sodered a wire on the secondary fuse then when I powered it up the picture came up but then it would go off and on. until I started seeing smoke from the bottom of the board and then I unpluged it took the board off turned it around and the 4431 was burned. but at least I got the picture to come up. because there was no display at all before. I ordered the 4431 from newark. now I have to order at least the 4 5707 and the fuse. all the caps they look good now if anyone knows where I can get the 5707 and the fuse. the fuse I do not know what the voltage or amps. wonder if anyone can help me with this information I would appreciate it. thanks in advance. god bless.

[Bobdee]

Re: Shorted HP L1955

Hello jesco d
This may help, there are more on ebay

http://cgi.ebay.co.uk/KIT-4-PCS-2SC5...3286.m63.l1177

can you let us know what the 4431 is, I have no board on hand, curious to find out
thxs

[Bobdee]

Re: Shorted HP L1955

Its ok jesco, I think I got what 4431 is = mosfet Q805
thxs

[jesco_d]

Re: Shorted HP L1955

Hi there, thank you for your reply.my question is on this kit it has 2 extra transistors that I don't see on my board. one more question if you don't mind. when the mosfet 4431 blew out it kind of burn the traces underneth the chip on one side. so I am not really sure about the pin out look like on one side 3 of the pins they are together and on the other side I am not sure since the traces were burned. I just wanted to know if you know anything about it. thanks

[Bobdee]

Re: Shorted HP L1955

Hello jesco
Data sheet from Krankshaft on page 2 of this thread is the 4431,it should help you, also the way it is soldered on board, some pins can be soldered together so that might help with data sheet

the kit I posted has the c5707 and fuse, but I now know yours is a 4A fuse according to photo on page 3 of this thread, and kit has 3A, but the seller has 4A and 5A fuses in pks of 4, I mention both because on page 12 of this thread a 5A fuse is mentioned but the photo clearly shows 4A printed on it

the other transistor FUs are not for your board but handy for many dell benqs and other monitors you may fix
hope it helps

[mjsbv]

Re: Shorted HP L1955

The original fuse was a 5 Amp. The 4 A in the picture in post 3 was a temporary one I put in. I didn't want to blow the one 5A replacement I had while troubleshooting the board.

[Bobdee]

Re: Shorted HP L1955

Hello mjsvb
Thanks for clearing that 4A fuse issue for me and others,
I noticed in a previous post of yours, that you hit on microscopes

I did resolder the transformer pins but will look at the grey caps too. I should have taken a picture of the cracked transformer pins in the microscope but didn't think of it till it was too late.

May I ask if the picture of the board with 4A fuse on is taken with microscope that is connected by USB to comp ???

I ask because I have been thinking of buying one of these for some time,for searching cracked solder joints to save my eyes a bit, and for posting pictures of circuit/boards ect,

Can you recommend if this is a good way to go about this ???

many thanks
bob

[Krankshaft]

Re: Shorted HP L1955

A stereo optic microscope would be best never thought about it that way it's a pretty good idea.

My vision is pretty good but a microscope would make it less time consuming.

When the mosfet 4431 blew out it kind of burn the traces underneth the chip on one side. so I am not really sure about the pin out look like on one side 3 of the pins they are together and on the other side I am not sure since the traces were burned.

Using an unsuitable replacement (and bridging a fuse) it's just not a good idea. Wedging a FLO (fuse like object) into the fuse holder or bridging a trace to "get it working again" will FRY equipment in most circumstances.

The fuse blew for a reason and hopefully nothing else is broken now. You could have soldered a light bulb across the fuse and it may have prevented the magic smoke and saved the FET from overcurrent.

In most cases you can completely FUBAR equipment by doing this.

Anyhow check the traces on the other MOSFET the circuits are identical.

One MOSFET controls one side of the inverter.

[mjsbv]

Re: Shorted HP L1955

Unfortunatly I didn't take a picture with the microscope to show the cracked solder joints and I fixed them before I thought of it. I used a stereo microscope with about a 12x zoom lense to look at it. That scope has a CCD camera that also looks through it and outputs the scene to a video monitor and a video image capture printer. A nice tool I have access to at work. I have found however that a high megapixel camera with good macro capibility can be pretty good poor mans microscope when the image is enlarged onscreen. The pictures in the earlier post were taken with a Canon powershot A620.

mjsbv

[mindless]

Re: Shorted HP L1955

please explain how to open the screen?

Mine works OK but loud buzzing noise is heard from inside

[firerx]

Re: Shorted HP L1955

Thank you guys for you help with the monitor caps issue. I replaced all the capacitors on the power board and my monitoris good as new. I also concur, use 105c caps on this board.

[orangelife2011]

Re: Shorted HP L1955

dell 1800 and 1801 inverter fix have replaced 6 pin IC now flashing power light no screen
no Bad Capacitors. Help

[retiredcaps]

Re: Shorted HP L1955

dell 1800 and 1801 inverter fix have replaced 6 pin IC now flashing power light no screen
no Bad Capacitors. Help

First, this thread is the HP1955. Start a new thread for you Dell monitor.

Second, write in full sentences so we can understand what you are saying. This is not twitter.

Third, post clear focused pictures AFTER reading

https://www.badcaps.net/forum/showthread.php?t=1868

Please do not post pictures inline.

Take your boards to a window on a sunny day, turn flash off, and use macro mode. Take a top down view of all your boards (front and back). Make sure the photo is legible so that we can read the PCB printing clearly. A shutter speed of 1/125 or faster will produce nice clear focus pictures. Try to get a photo that is 2000x2000 resolution or as close as possible.

Here is an example of the pictures we want.

https://www.badcaps.net/forum/showpos...94&postcount=1