Dell e172FPb Actual Schematics

[Rtech]

Re: Dell e172FPb Actual Schematics

Snow still in places.lowest temps in December for a 100years.All the voltage readings you gave look good.Use the 3v battery as you alreadty have.You need both CCFL assemblies plugged in...if you only use one, the lamp will flash and go off.
Merry Xmas

[lcdman]

Re: Dell e172FPb Actual Schematics

Hello To Both Fellas Over The Pond,

I'm not getting a full 3.3VDC or 5VDC at pins 7,8,9,10 on all of my current batch of PCBs? Maybe a component is not up to snuff causing the reduction in voltage to CN701 connection hub? So you want me to put a jumper wire between pin 9 or 10 to pin 2? Plug the board in and wait, then hook up the CCFL? Do I need both CCFL assemblies hooked up? I've been using only one CCFL assembly. Is it still snowing over by you guys?

Happy Holidays To All.........
lcdman

[Mikeley]

Re: Dell e172FPb Actual Schematics

Ok you veriified earlier that 3.3V is available from the PSU at the logic board connector! Make a connection between pin 9 or 10 to pin 2. Solder a wire to one end and power up, make the connection, CCFL should come on. Allow the PSU to come on before trying to start the CCFL's. Dont think you need the batteries!

Merry Christmas and happy holidays!

[Rtech]

Re: Dell e172FPb Actual Schematics

I use two 1.5v Batteries in series, and have never had a problem lighting the tubes,add another 1,5v battery if you wish, and see what happens !!

[lcdman]

Re: Dell e172FPb Actual Schematics

Hello All,

Thanks for everybody's advice and using my own words against me! I also already know about the transformers and dry joints. Remember I did successfully repair one Dell e172FPb. Changed all the C5707 and the FU9024N as well as PF751 fuse & re-soldered ALL the transformers on the board. Did the same with all of my boards since. I checked for bad caps with a capacitor meter. Some still passed, but I went ahead and went back and changed all the caps with Nichicon,Rubycon,Panasonic caps.
I'm waiting for some new CCFls to arrive then I'll retry. What about the 3VDC trigger? Should I be using 5VDC instead? Any tips or cracks???

Till Next Time,
lcdman

[EGuevarae]

Re: Dell e172FPb Actual Schematics

...replaced all bad caps,...

With what caps, just out of curiosity?

[Mikeley]

Re: Dell e172FPb Actual Schematics

lcdman,

I've fixed two of these Dell E172'S recently and apparently have a stack of 'em waiting!

Now, in the first case one pair of 2SC5707's was shorted out. Simply check this component by setting your DMM to 200 ohms range or thereabouts, and check resistance between each of the 3 pins. If you get a low value reading between any two pins, remove the transistor and recheck out of the circuit. It's a dud if you measure a low value. Other components in circuit can cause low readings.

In the case of the fet, do the same check. FETS can fail differently, but lets not get into that just yet since you already replaced them.

In my second recent case, 4 1000uF 10v/16v and 2 470uF 35v capacitors had low capacitance and/or high ESR values. Simply renewing these restored full operation. I'm curious, did you repace all caps or just the buldged ones? How did you check them?

In both my cases, dry joints were a problem. Shout if you dont' know what it meant by 'dry joint'. As Eguevare says, this is a very common problem on this model/versions. I too found loose components when one monitor was opened. In fact one transistor was missing because the owner heard it rattling inside and took it out! Story for the pub.

Inspect all solder joints under good light and use a magnifier to help the eyes. The 4 inverter transformers, capacitors, resistors, inductor and diode etc on primary side should be cleaned up with solder wick and resoldered carefully. No harm to do secondary side also... a tad tedious, but will ensure that the C5707's last a bit longer.

After doing all this, and making sure that all soldering is good, then you can get stuck into some deeper troubleshooting if problem persists.

I just would swap this PCB with a PCB you have fixed, to confirm the CCFL's on this LCD are in good working order.

[EGuevarae]

Re: Dell e172FPb Actual Schematics

I don't have a "my way"....
With all the very knowledgeable fellas on this site, no one has an actual pin-out of this connection point for any Dell e172___ or e173___

Bad answer. Some of us do, but it will do no good if you don't know what to do with it.

... I've been told that I was wrong!

Yes you are.

Is there a way to put a jumper or switch across the pins on CN701 to try and make a CCFL come on without attaching a logic board?

Yes, applying 5v to the BL_ON pin.RTech said that already,only that he said 3v...

I changed all the electrolytic caps, all (4) C5707, both of the FU9024N.....
Can you give me any hints or advice on any of these items?

Again,use the search function. You need to check the 07s,the FUs,but also have to resolder the transformers because it is common on those boards to have cold solder points on them

**** Also, if one of the 4 lamps is bad, the inverter will shut down even if all is working correctly.You need a good set of lamps.
Do you happen to have a fully working monitor? You need a tested set of lamps.

[Rtech]

Re: Dell e172FPb Actual Schematics

When checking the 5607's and the FU,with the diode checker..provided you do not get a short cct,,ie zero reading then they are probably ok.Are you testing all these bpards with the same ccfl's ??????You really need some good ones, to eliminate the ones you are using,as they seem to be the common denominator,if you only have the one set ?/

[lcdman]

Re: Dell e172FPb Actual Schematics

Hello,

First of all many thanks to Mr. Rtech from the U.K.! I tried your last suggestion.
I got a handful of PCBs to light the CCFL. But they went out after a few seconds? I changed all the electrolytic caps, all (4) C5707, both of the FU9024N. My question now is, I have a Fluke DMM that has a diode setting. It beeps and gives a voltage usually on both sides of the C5707 and the FU9024N when in circuit. Is this the right way to check these? Also what about IC701, D702,D701,Q601? Can you give me any hints or advice on any of these items?

Thanks Again To All,
lcdman

[Rtech]

Re: Dell e172FPb Actual Schematics

You need to apply and external voltage to the CN701,usually 3v DC(perhaps fom 2 batteries),between the pins B/L ON and one of the Ground pins...this will light the B/L's..if all is well with the board.

[lcdman]

Re: Dell e172FPb Actual Schematics

Hello Fellas,

Sorry for the delay in posting anything new! Been busy with Christmas coming and all. Thank you for the pin-out! I took the pin-out from the previous post and tested the boards I currently have on my bench. Here are my results:

48.L9202.A01 = 5.01/3.293VDC
48.I9202.A01 = 4.96/3.304VDC
48.L9202.A02 = 4.98/3.289VDC
48.L9202.A11 = 5.01/3.289VDC
48.L9202.A11 = 5.02/3.297VDC
48.L9202.A11 = 5.01/3.309VDC (this PCB had just been disassembled from monitor)
48.L9202.A12 = 5.01/3.292VDC
48.L0J02.A12 = 5.12/3.299VDC
48.L0J02.A12 = 5.13/3.293VDC

Is there a way to put a jumper or switch across the pins on CN701 to try and make a CCFL come on without attaching a logic board? I only ask because in past posts I've smoked a logic board trying to make a complete monitor! Probably has a short. Any advise?

Thanks & Happy Holidays
lcdman

[Rtech]

Re: Dell e172FPb Actual Schematics

From my cct diagram,pinouts as follows:-
1)backlight adjust(dim)
2)Backlight ON
3)Pins 3,4,5 and 6 ground(earth)
4)Pin 7 and 8, 5volts Dc
5)Pin 9 and 10,3.3volts DC
So initially just measure Pins 7,8 9 and 10 with the meter neg lead on the ground.

[lcdman]

Re: Dell e172FPb Actual Schematics

Hello Yet Again,

I don't have a "my way". When I measured a working board I got millivolt AC.
And from the posts since, I've been told that I was wrong! I do see that the terminals soldered to the board translate to just 5 connection points not 10 separate connections. So I should be measuring DC in milivolts or volts? Any other suggestions? This can't be too complicated right? With all the very knowledgeable fellas on this site, no one has an actual pin-out of this connection point for any Dell e172___ or e173___? I've seen other posts about "Benq monitors" but there were more pins than the CN701.

Thanks Again Guys,
lcdman

[PlainBill]

Re: Dell e172FPb Actual Schematics

Hello,

I marked the photo with the pin numbers as seen on the top of board, left and right side of the CN701 connector. There is no markings on that specific area of the bottom of this board other than CN701 thats also on the top of the board.

Thanks,
lcdman

OK, we'll do it your way. Measure the voltage from each pin to ground.

PlainBill

[EGuevarae]

Re: Dell e172FPb Actual Schematics

Hello,

I marked the photo with the pin numbers as seen on the top of board, left and right side of the CN701 connector. There is no markings on that specific area of the bottom of this board other than CN701 thats also on the top of the board.

Thanks,
lcdman

Use the search function and search "CN701".Plenty of info....

[lcdman]

Re: Dell e172FPb Actual Schematics

Hello,

I marked the photo with the pin numbers as seen on the top of board, left and right side of the CN701 connector. There is no markings on that specific area of the bottom of this board other than CN701 thats also on the top of the board.

Thanks,
lcdman

[EGuevarae]

Re: Dell e172FPb Actual Schematics

Hello All & Mr. Bill,

As far as I know the 5 PS/I,logic boards,LCD panel are good? There might be a CCFL out? But I won't know till I get a PS/I working correctly. I'll try yet again with a picture. I figured out that this site won't accept my photos as I shot them. They too good of quality and especially too big file size to work within the specs you guys require. I'm enclosing a almost descent picture of the CN701 connection point between the PS/I and the logic board. Please tell me which pins and what type of measurement to try, if its not too much trouble.

Chao,
lcdman

You need a top & bottom picture.If too big (pixel) ,resize them. Connectors sometimes say what pin is for what ...

[lcdman]

Re: Dell e172FPb Actual Schematics

Hello All & Mr. Bill,

As far as I know the 5 PS/I,logic boards,LCD panel are good? There might be a CCFL out? But I won't know till I get a PS/I working correctly. I'll try yet again with a picture. I figured out that this site won't accept my photos as I shot them. They too good of quality and especially too big file size to work within the specs you guys require. I'm enclosing a almost descent picture of the CN701 connection point between the PS/I and the logic board. Please tell me which pins and what type of measurement to try, if its not too much trouble.

Chao,
lcdman

[PlainBill]

Re: Dell e172FPb Actual Schematics

Hello All,

I hooked up a "power supply" to a logic board and then to the screen, etc.
Plugged it in and the logic board started to smoke. So I very quickly unplugged the PSB and went back to the drawing board. Like I stated before the PSB probably had a short after attempting to repair loose C5707 and FU9024 that were found after dissembling this monitor in the first place. So then I went about checking and replacing all the (4) C5707, the (2) FU9024N and the radial caps that had possibly failed. After doing those redos I thought that it would be better to check the voltages before ruining another logic board, they are too expensive to replace. Since that attempt I then fixed the other 5 boards that I tried to post pictures here. If you need more info, I know you guys will tell me!

Have A Good One,
lcdman

NOW it's clearer. Good idea NOT trying another logic card on that good power supply / inverter (PS/I) card. Lots of people would have blown two or three logic cards.

Let me verify this. You have 5 good PS/I cards, 5 good logic cards, and 6 good panels. Is that correct?

If it is, the most likely cause is excessive voltage out of the power supply. You can test it without anything hooked up to the card (except a power cord). Check the voltages on the connector to the logic card. If you need help idetifying the points to test, attach good pictures (as close to 2000 x 2000 as possible) and we'll identify the proper points.

I would suggest that a good LCD panel is probably worth more than the cost of repairing the power supply and replacing the logic card.

PlainBill