Dell E172FPb

[ratdude747]

Re: Dell E172FPb

in english?

[flacox2]

Re: Dell E172FPb

este tipo de monitores siempre se le queman esos transistores npn, la solucion mejor es cambiarselos todos, los transistores de monitores de 15 puden servir, los que son 5706 funcionan perfecto, ya los he probado

[ratdude747]

Re: Dell E172FPb

still running well... no issues.

[ratdude747]

Re: Dell E172FPb

the kit came in today.

I didn't fuss with the fuse. otherwise, I replaced all 6 transistors.

it works again.. knock on wood.

lesson: with transistors, replace like with like.

i guess that makes my first LCD job a success?

edit- video quality isn't too shabby. my friend will be happy that he gets his monitor back in working condition

[ratdude747]

Re: Dell E172FPb

Wow!!! Lots of things to cover. As you have discovered, the best source of the transistors is on eBay. If you examine the board, you will see each transformer has it's own pair of C5707 transistors and FU9024N transistor. Definitely replace both C5707s for this transformer, and I would urge you to replace the FU9024N also, it took a current surge. It shouldn't be necessary to replace the other set if they aren't shorted. And unless the fuse is open, there is no point in replacing that.

By the way, the voltage rating of a fuse is the voltage it can interrupt. This circuit handles 12 volts, so either a 250V or 125V fuse is more than adequate.

PlainBill

the kit was cheap enough as it is; at $5 a kit, since this is only one unit I am servicing, the cost is negligible. without my trusty multimeter I am kinda helpless to test things...

I will order the kit and see what i can do.

[PlainBill]

Re: Dell E172FPb

i found the for sure problem

my "replacement" transistor's ground plate thing is discolored... that tramsistor toasted itself.

sounds like i need to buy the right transistors.

this look ok:

a LONG url

I can't find that transistor or the other one in the kit anywhere else...

i never checked the fuse but it looks as if I better get a multimeter (my old one is in somebody else's possession right now). does the fuse in the kit look ok (same specs other than the voltage, the stock one is 250v, this one is 125)?

Wow!!! Lots of things to cover. As you have discovered, the best source of the transistors is on eBay. If you examine the board, you will see each transformer has it's own pair of C5707 transistors and FU9024N transistor. Definitely replace both C5707s for this transformer, and I would urge you to replace the FU9024N also, it took a current surge. It shouldn't be necessary to replace the other set if they aren't shorted. And unless the fuse is open, there is no point in replacing that.

By the way, the voltage rating of a fuse is the voltage it can interrupt. This circuit handles 12 volts, so either a 250V or 125V fuse is more than adequate.

PlainBill

[ratdude747]

Re: Dell E172FPb

i found the for sure problem

my "replacement" transistor's ground plate thing is discolored... that tramsistor toasted itself.

sounds like i need to buy the right transistors.

this look ok:

a LONG url

I can't find that transistor or the other one in the kit anywhere else...

i never checked the fuse but it looks as if I better get a multimeter (my old one is in somebody else's possession right now). does the fuse in the kit look ok (same specs other than the voltage, the stock one is 250v, this one is 125)?

[PlainBill]

Re: Dell E172FPb

i resoldered the transformers already. as in desoldering the transformer, removing it, and soldering it back in. the new solder should have fixed that.

Yes, now they won't cause the transistors to fail. However, you must still have suitable transistors or the oscillator won't start.

My point was 'better' transistors aren't necessary, the originals are quite adequate. It's the poor job of soldering that is doing the damage.

PlainBill

[ratdude747]

Re: Dell E172FPb

i resoldered the transformers already. as in desoldering the transformer, removing it, and soldering it back in. the new solder should have fixed that.

[PlainBill]

Re: Dell E172FPb

i think you are right. I feel stupid as all this time later, my failure to do things the right way may be why it still is dead.

I still have the unit in my possession and I tried it again.

it is good for maybe 10 sec before the backlights go out. after the test i smelled burning electronics near the transistors.

the 1 transistor that fried and i swapped for the larger transistor is a c5707. is it recommended that i replace all 4 with the exact same transistor or is there a compatible one that is less prone to failure? it seems they fail a lot and I would rather not have to replace them all the time (it belongs to a buddy who had it in his closet).

I thought that as long as I had the pnp/npn part good and it was the same or bigger all would be ok. i guess that and the fact I only replaced one may be why it still goes 10 sec to black?

This design uses a circuit called a Royer Oscillator. It requires two transistors with similar characteristics. With some care, it would be possible to select suitable transistors, but pulling some NPN transistor out of the drawer isn't going to cut it.

The root problem is not the transistors, it's the crappy solder job on the transformers.

PlainBill

[ratdude747]

Re: Dell E172FPb

Considering the application, they should ALWAYS be replaced in pairs, and with the proper part numbers.

PlainBill

i think you are right. I feel stupid as all this time later, my failure to do things the right way may be why it still is dead.

I still have the unit in my possession and I tried it again.

it is good for maybe 10 sec before the backlights go out. after the test i smelled burning electronics near the transistors.

the 1 transistor that fried and i swapped for the larger transistor is a c5707. is it recommended that i replace all 4 with the exact same transistor or is there a compatible one that is less prone to failure? it seems they fail a lot and I would rather not have to replace them all the time (it belongs to a buddy who had it in his closet).

I thought that as long as I had the pnp/npn part good and it was the same or bigger all would be ok. i guess that and the fact I only replaced one may be why it still goes 10 sec to black?

[PlainBill]

Re: Dell E172FPb

I don't know for sure but these transistors may need to be replaced in pairs.

Considering the application, they should ALWAYS be replaced in pairs, and with the proper part numbers.

PlainBill

[alexanna]

Re: Dell E172FPb

I don’t know for sure but these transistors may need to be replaced in pairs.

[alexanna]

Re: Dell E172FPb

the trannies already have been resoldered and checked.

3 of the 5707's were tested good. one was replaced.

Did you see if the transistors that you installed have not failed again? You do not have to remove from circuit.
Something I don't see mentioned often on these monitors. Is to check and or re solder, the gray poly capacitors that sit right between the C5707 transistors. I have notice on more than one occasion loosens on the solder pads.

[ratdude747]

Re: Dell E172FPb

the trannies already have been resoldered and checked.

3 of the 5707's were tested good. one was replaced.

[seanc]

Re: Dell E172FPb

Change all the 2SC5707 after having double checked the transformer soldering and other solder joints.

Transformers, 2SC5707 and a pico fuse is all that's *usually* needed in these.

[ratdude747]

Re: Dell E172FPb

spoke too soon.

it is now a case of 20sec to black... what now? caps?

[ratdude747]

Re: Dell E172FPb

first faiure found

one of the 4 inveter area transistors is shorted out. the other 3 pass fine. i tested them out of circuit.

the part no. is c5707.


i had a sanyo 2SC4106 in my junk bin. popped it in, success.

I DONE FIXED IT!!!

i will run it a while to see if it holds.

[ratdude747]

Re: Dell E172FPb

I don't do ebay repair kits. too many scams.

my camera died so no pics for now... I think i will start with a recap.

[hoadle]

Re: Dell E172FPb

Here the website for you Dell E172FPb
http://syscon.wordpress.com/2007/07/...klight-repair/
go to ebay buy the repair kit
http://cgi.ebay.com/REPAIR-KIT-E172F...item3355ff735c