Dell E171FP No power

[Welchs101]

Re: Dell E171FP No power

Bill,

Thanks again. I learned somethings so thanks.

I did have one question i wanted to ask. Why did you have me put the resistor across the 2200uF cap instead of the other row of caps? Just curious.

thanks again.

[Welchs101]

Re: Dell E171FP No power

One other question



From this link pin1 is "SD=shutdown" and pin2=vin. Should they be shorted? Because they are.

[PlainBill]

Re: Dell E171FP No power

Bill,

Thanks again. I learned somethings so thanks.

I did have one question i wanted to ask. Why did you have me put the resistor across the 2200uF cap instead of the other row of caps? Just curious.

thanks again.

This goes back to SMPS design. The output voltage of the supply is fed back to the controller. If the output voltage is too low, the width of the drive pulses are increased to pass more energy from the primary side to the secondary. If the output is too high, the pulse width is reduced. If you have a single output, design is easy - regulate the single output. If you have multiple outputs it gets more difficult. The design can either regulate one output and let the others wander, or use multiple controllers, transformers, etc. In most applications one voltage is critical, usually the 5 volt supply. That's the one I had you load.

PlainBill

[PlainBill]

Re: Dell E171FP No power

One other question



From this link pin1 is "SD=shutdown" and pin2=vin. Should they be shorted? Because they are.

Yes. Notice the line over SD. That indicates an active low signal. In other words, pulling pin 1 to ground will turn off the regulator. By tying it to Vin, it's always on.

PlainBill

[Welchs101]

Re: Dell E171FP No power

thanks! learned something new again!

[syclonejim]

Re: Dell E171FP No power

I don't know if you ever got your E171FP power board to work, but I have fixed twenty to thirty of these power supplies. The problem is always the 50 volt caps I have circled in red.

[silverbulit]

Re: Dell E171FP No power

Hey guys (and gals),

I just wanted to let you know that I replaced the capacitors that syclonejim was referring to and my monitor is working perfectly after being completely dead. Thanks for your help!

Silver

[billy66]

Re: Dell E171FP No power

I have a Samsung 151s monitor with this exact same boards. The Mosfet in bottom right corner was bad (see syclonejim's pic). I haven't replaced yet, as the Mosfet is no longer available (MTP2955V). I will also replace the caps as suggested. I just wanted to add the Samsung monitor to this tread so others when searching for that monitor will come across this.

Thanks.

[trickymint]

Re: Dell E171FP No power

Hi, had a similar problem with an E171FP bought on eBay. On first power up there was a pop from the back of the monitor and a subsequent electrical burning odour. It was going to cost me postage to return to seller with no guarantee of a replacement or money back so decided on repair.

Opened it up and discovered bulging C5 (100uF, 400V, CapXon) and blown 3.15A fuses on power/inverter board. In addition found bulging 220uF, 25V, Teapo on CFL driver board.

Replaced C5 with 47uF, 450V (closest match available from local store) and 220uF caps. Couldn't get PCB fuses readily so replaced with 5A fuse wire links (naughty I know).

Monitor now working.

[billy66]

Re: Dell E171FP No power

I replaced all the caps on the power board and the mosfet Q1... monitor is now alive.

[printone2]

Re: Dell E171FP No power

I have included pics as well because i am notorius for looking at a partnumber and getting it wrong.

From what i can tell with magnifying glass:
Part1)
26AT
LBBB

Parts2)3)4)
BA033
2B 29

Part5)
7805C
NLEC239


If this does not answer your question or you need more info just let me know.

I too thought I had a power supply problem, but the real problem was on the image board. I compared a working power supply output and found the two 12 volt rails were showing 15.9 volts. When I swapped the image boards the panel would not light up. The problem was a bad cap on the image board at C163 a 47uf 6.3v 6mmx6mm. It was reading 2.48v on the good image board, but only 1.52v on the bad one. When I pulled the cap it registered 38uf, so I replaced it and now my panel lights up.

[skisabeth]

Re: Dell E171FP No power

I too thought I had a power supply problem, but the real problem was on the image board. I compared a working power supply output and found the two 12 volt rails were showing 15.9 volts. When I swapped the image boards the panel would not light up. The problem was a bad cap on the image board at C163 a 47uf 6.3v 6mmx6mm. It was reading 2.48v on the good image board, but only 1.52v on the bad one. When I pulled the cap it registered 38uf, so I replaced it and now my panel lights up.

My Monitor too had 15v on 12 v rail and replacing C163 fixed it eventhough the cap checked good on tester (53uf)