Buying transistor advice Dell E173FPc - 2 Seconds to Black

[bigcap]

Dell E173FPc - 2 Seconds to Black

what I found was

top ccfls come on for 2 seconds then off even though some driver pin solders had melted...now been resoldered

the bottom ccfls just don't come on at all. driver pins and solder look solid. tested ccfls on another display and there all good.

before fault the screen seemed to be a lot brighter than my other identical monitor

I'm basically looking for advice on replacing the 4 c5706 transistors.
The one on the board are labeled c5706 with 4k printed on them.

Can I replace with c5706 8k as I have no idea what the 4k or 8k stand for.

was looking to get these

http://www.ebay.co.uk/itm/C5706-3-Pi...item1c3aeb13ed

or

http://www.ebay.co.uk/itm/2SC5706-C5...item4605afb838

or should I go for c5707

http://www.ebay.co.uk/itm/C5707-Tran...48355501&rt=nc


if anyone has a better link to the ones to get in UK, I'd appreciate very much.

[budm]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

I use C5707 in place of C5706 for all my repairs.
You also check the tunning caps (grey or white or yellow) to make sure it still have correct capacitance, and resolder all the joints.
http://s807.photobucket.com/user/bud...?sort=3&page=1

[bigcap]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

Hi budm thanks for replying.

whith regards to the tuning cap I think my board is different here's my board

are the tuning caps the 2 blue ones where the 4 transistors im gonna replace are... in-between the drivers on the left side of the pcb board?

also I checked out the C5707 transistors. am I right in thinking they are an improved model on the c5706 ?
as I seem to be able to get the c5706 in the UK would it be the preferred replacement and better for the ccfls lamps in the long term due to the small difference in specs ? or just go for the c5707 as there better all round spec wise for the ccfl lamps?

http://pdf1.alldatasheet.com/datashe...I/2SC5706.html

http://pdf1.alldatasheet.com/datashe...O/2SC5707.html

[budm]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

"are the tuning caps the 2 blue ones where the 4 transistors im gonna replace are... in-between the drivers on the left side of the pcb board?" Yes.
5707 has better spec but 5706 original is fine.

[bigcap]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

thanks budm,

think I will go with your suggestion c5707 as there cheaper and I get a few extras to put in my virgining electronics soldering tool box.

Probably a stupid question but how do I measure the 2 blue caps? can I use a multimeter dmm.

I just tried ie set to 200 on ohms scale, probes on each leg solder joint of blue tuning cap... my value 1 on dmm being open ...when probes are on legs I get .000 so closed circuit

im almost sure ive done this completely wrong and probably need to remove them from board and have a different type of meter?

caps are 7c184j 250V

feeling a little embarrassed now but im hear to learn. :P

[budm]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

You use capacitance meter to verify that the capacitance is still within the spec of the cap, it usually loses its capacitance when it goes bad.

[bigcap]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

hi budm

got the transistors

these are results for in circuit of old transistors dmm set to 2k

B + to E - = .608, reversed = .431
B+ to c- = .246, reversed = .246

when removed and tested on bench

B + to E - = .760, reversed = 1
B+ to c- = .756, reversed = 1

1) I think these are all good? as new ones test .763 and .762 and on reverse is 1 on bench.

2) do the 2 blue tuning caps cause these results when testing in sit u? I don't have a caps test meter to test them but does it indicate its them?

3) if you look at the photo above closely the pins solder burnt out on the driver and resistor it looks like. I resoldered. but that cffl came on and went off after 2 seconds. The other side looks fine but the ccfl doesn't coming on.
would this indicate something else is going on, on the board....or is it the blue tuning caps?

see no point yet in putting new c5707s in as yet.

What do u recommend?

[Lumberjack777]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

Are you saying you have tested the C5706's on that board? That's almost ALWAYS the problem on that board. At least one has usually shorted. Here's retiredcaps method of testing from his "2 seconds to black" guide.

"2) Shorted Transistors/MOSFETs
------------------------------------

On some LCD brands (example: Benq) the transistors (C5707) are sometimes shorted. Transistors are usually marked with a "Q" designation.

If you have a manual range multimeter, set it to 200 ohms (two hundred). You can test for shorted transistors "in circuit" (with power off and unplugged)

a) put black probe on pin 1 and red probe on pin 2 - read/record ohm
b) put black probe on pin 1 and red probe on pin 3 - read/record ohm
c) put black probe on pin 2 and red probe on pin 3 - read/record ohm

If any ohm reading is less than 30 ohm you might have shorted transistor. Remove the transistor and repeat the tests out of circuit to verify.

Note: a shorted transistor would likely cause a very brief flash of the backlight or no backlight."

[budm]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

"
these are results for in circuit of old transistors dmm set to 2k

B + to E - = .608, reversed = .431
B+ to c- = .246, reversed = .246

when removed and tested on bench

B + to E - = .760, reversed = 1
B+ to c- = .756, reversed = 1"

How about testing them off the board and also between E and C.

[bigcap]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

Hi budm,

I did check C and E results seemed ok. Decided to change all and removed them. tested all off board and guess what?.... one was clearly shorted. You were right Lumberjack777 at least one....thanks for chiming in.

its been a day and a half with new ones in and I can gladly report that you guys and badcaps can add another successfully fix dell monitor to the tally chart.

Much thanks!

Now to attempt a motherboard fix which i'll post in appropriate forum.

Thanks again!!!

[budm]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

Thanks for the repair follow-up and I am glad that you can repair it.

[3Focus1]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

I am new at this. I am a second year EE student at LeTourneau University and don't know the best places to look for parts.

I have a monitor, Dell E173fpc which won't stay on, it sort of fades out. No blinking of the power light. I could just buy a used monitor for 20-30$, but I'd like to troubleshoot this one for practice. The power supply board 715L1283-4. Regular capacitors seem fine. No bulging etc. However,

1. C5706 5G Transistor bad? Can use C5707?

2. 7C184J 250V 0F ceramic capacitor Shorted. Tested by ohmeter while on circuit board (which I know is a no-no, but looking for any continuity). Looked at Mouser and found only a 50V, but not a 250V. Puzzling. Checked other sources too.

3. 80ll15t-7-ys g 0523 Bad transformer, 1 post blackened some solder missing. Already de-soldered and removed.

I don't know which happened first, the transformer went bad or the capacitor, or maybe even the transistor. I think FB901 is a fuse, but uncertain. It is very small. Anyway, it appears to be good. Of course, its a Dell, so I think they're pretty tight with proprietary parts breakdowns,etc though not certain. So just winging it really.

Thanks,
Scott

[budm]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

1) 2sc5707 is OK to use, see post 4.
2) Take the cap out of circuit and check the resistance.
3) Upload the pictures of the bad transformer and the board.
4) FP901 is the fuse and it should show <1 Ohm, so check that out first, it is 3A FUSE (BELFUSE).
Board is know for bad solder joints and bad caps in the Royer Osc. section.
Did you read the whole thread?

[3Focus1]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black



I'll look more closely at the other posts.


Edit: I see the image is not uploading. I'll try to figure that one out.

[stj]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

lol
upload the photo, dont link it to your desktop!

[3Focus1]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

Diagnostic picture.

[3Focus1]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

A couple more.

[budm]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

The brown spot at the transformer leg is due to poor solder joints so it develop contact resistance which will heat up. As indicated, that board is known for lots of bad solder joints, just look real close at the legs of the parts for cracked solder ring around the leg of the parts.

[budm]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

BTW, those two blue tuning caps will show low resistance because it is connected in parallel with the transformer primary winding which has low DCR. You need to check the capacitance to make sure it is still within tolerance.

[stj]

Re: Buying transistor advice Dell E173FPc - 2 Seconds to Black

those capacitors arent ceramic, they are plastic film.
probably polypropylene or polyester.