Dell 1707FPt No Power

[LDSisHere]

Re: Dell 1707FPt No Power

Okay, I did some testing with my Fluke 113 and 12.

As I expected in some circuits, the Fluke 113 and 12 when used in Vchek mode will not properly report some measurements because it is working 100% as designed.

The Fluke 113 is in low impedance mode all the time (optional for Fluke 12). As such it can affect the circuit under measurement. To see why, have a read through

http://www.talkingelectronics.com/pr...onents.html#12

The Fluke 113 has a 3k ohm input impedance. Most digital multimeters have a 10M ohm input impedance. The Fluke 12 has a 2k ohm input impedance in Vchek mode and 10M ohm for DCV "manual" mode.

In my tests, the Fluke 113 and 12 (when using Vchek) will both fail to measure DCV properly in some circuits (i.e. it shows 0.0V DC). When I switch the Fluke 12 to "manual" DCV mode (with input impedance of 10M ohm), it measures the DCV properly.

So if you plan to do more electronics work, you may ask the gifter to give you the receipt for the 113 and exchange it for something else like a Fluke 115 (albeit more money).

That information explains a whole lot, at least I know the problem was the 113 and not my imagination when I had mine. This is the still the only Fluke meter I have ever disliked (so far).

@maybenever

I ran into the same problems you are experiencing a while back ago when I made the mistake of buying the Fluke 113. It is probably a good meter if you are an electrician or do HVAC repair but worthless for my purposes. I did discover I could get the thing to give me a voltage reading in the situations you are having problems with if I reversed the leads but that could ultimately cause more problems than it solves.

My solution was to replace it. I have since picked up two good meters from a local pawn shop and keep wanting to go look for more even though I do not really need them. I recently discovered the test leads alone that came with my 175 cost more new than what I gave for the meter with the leads included.

https://www.badcaps.net/forum/showthread.php?t=26191

[maybenever]

Re: Dell 1707FPt No Power

The Fluke was a gift from my wife, she thought she did good, I thought she did good. I destroyed the package getting it out, so guess I'll keep it. I'm a residential plumber and electrician by trade, so I can use it., but it's on my dislike list too.
Back to the Dell monitor, I found a new PS board on ebay for $15 & free shipping. Got it today, what are the odds of getting a board with the exact same issues as my old board? It looked good, all KY caps, but the output voltage is bouncing between 5 & 5.3 volts. Went ahead and connected it up, power LED came on as soon as it was plugged to AC, wouldn't turn off, unplugged and plugged in again, no power LED and it won't come on again. What are the odds, I'll try to get it replaced.

[maybenever]

Re: Dell 1707FPt No Power

Got a responce from my ebay seller, they are giving me full credit on my purchase. I asked what to do with this bad board, and I still need a board. I got this reply
[QUOTE]You can just throw the bad one away.

These batch of boards that we have are probably bad that we are looking for solutions to test them further. If you purchase another one from us, it is very likely that it will have the same problem again.

Therefore, if you need another one, we suggest that you purchase one from other seller.

Thank you for your understanding[/QUOTE
Ain't that something.

[retiredcaps]

Re: Dell 1707FPt No Power

Got a responce from my ebay seller, they are giving me full credit on my purchase.

Please name the ebay seller because that is a seller I would want to do business with in the future. Most sellers would not be some honest about their stock.

The only thing really left to test are the voltage regulators on the main board (just to rule them out).

[maybenever]

Re: Dell 1707FPt No Power

Please name the ebay seller because that is a seller I would want to do business with in the future. Most sellers would not be some honest about their stock.

The only thing really left to test are the voltage regulators on the main board (just to rule them out).

The money went to IT Express 101, and they are the ones that shipped it from Austin, TX, but great.pc.parts are the ones responding to my messages.
I've checked the voltage reg on main board, it's putting out 5.0vdc. What about voltage regs on the invertor board, where are they?
I started out with output voltage that dropped like a rock, reflowing & resoldering has stopped that. Now, just unstable output voltage. I've checked all caps, even the ones I pulled off the board, all have low ESR & correct uF readings (I now have an Atlas ESR70, so no more guessing). For some reason, I've commeted to figuring this one out, so please help, and thanks for the attention you've already given.

[selldoor]

Re: Dell 1707FPt No Power

Can we just recap on what you are working on - perhaps repost pictures top and bottom of any boards - what are you calling the inverter board? inverter transformers are on the power supply?
Test any fuses and give board numbers F100 F200 etc
Test and repost voltage on the main cap a) when plugged in b) when switched on.
Test and repost the voltages measured on the connector between the Power supply and main board a) when plugged in b) when switched on. c with the main board disconnected, d) with the main board connected but the panel -lvds cable unplugged.
If you have established which is the pson get a 500 ohm-1kohm resistor and with the main board diconnected jumper 5v to pson and see if the backlights come on.
If not, is there also a blon pin if so, in the same way jump 5v to Blon as well.
Best to set up the jumper then switch on the mains power.

[maybenever]

Re: Dell 1707FPt No Power

All fuses check good on PS board. Output voltages on PS pins (without main board connected) bounces between 5 & 5.3vdc. Voltage on large cap bounces between 166 & 168vdc. With main board connected, voltages on pin outs bounces between 4.7 & 5vdc, large cap voltages drops to 162 & 164vdc. Usually, the power button on front does nothing. Sometimes, the led comes on as soon as AC is connected, then won't turn off. When I connect spare ccfl and apply 3.1vdc to on pin, tubes flicker 3 times, about 3" of the tube on the wire connected end, then stop. I ordered a new PS board from ebay, has the same unstable voltage as old board. I had only a few minues today, I connected spare ccfls to new board & applied 3.1v to on pin. The tubes light from end to end (bright), for just a second, then go off. (better than old board).
I haven't tried many combinations with main board connected, didn't think it made much difference, if I can't get the backlights working. I hope this recap helps, I am thankful for all of yall's help.

[selldoor]

Re: Dell 1707FPt No Power

That is the old power supply? I meant a pic of the new one.

Does your ac in voltage wobble/bounce?

[maybenever]

Re: Dell 1707FPt No Power

That is the old power supply? I meant a pic of the new one.

Does your ac in voltage wobble/bounce?

Don't have any pictures of new board yet, it's exactly like my old board, only with all KY caps.
AC voltage bounces very little, between 123.2 to 123.1vac.

[retiredcaps]

Re: Dell 1707FPt No Power

I've checked the voltage reg on main board, it's putting out 5.0vdc. What about voltage regs on the invertor board, where are they?

I count three voltage regulators on the main board. Please report the readings as per my guide.

There are likely no voltage regulators on the inverter board. There may be a voltage regulator on the panel or t-con board.

[maybenever]

Re: Dell 1707FPt No Power

I count three voltage regulators on the main board. Please report the readings as per my guide.

There are likely no voltage regulators on the inverter board. There may be a voltage regulator on the panel or t-con board.

Would those be I301, I311, & I318? I've checked 318, it's 5v input, 3.3v output. I said 5v earlier, my bad. Have not checked the other two, if tha's the ones you are referring to.
Another correction, the voltage on the new board at the large cap is between 168.9 & 169.4vdc.
Her are photos of new board.

[selldoor]

Re: Dell 1707FPt No Power

I know you did some reflowing but wonder if you did enough.
If this is an early dell board it may be suffering the Benq/Dell cold joint
disease. Which means nearly all the primary side needs reflowing.
Remove as much old solder as you can and apply fresh to the points in the picture. Check it over with a magnifier.

[maybenever]

Re: Dell 1707FPt No Power

I know you did some reflowing but wonder if you did enough.
If this is an early dell board it may be suffering the Benq/Dell cold joint
disease. Which means nearly all the primary side needs reflowing.
Remove as much old solder as you can and apply fresh to the points in the picture. Check it over with a magnifier.

I applied flux and resoldered all these joints, but did not remove old solder. How about I do this on the new board, sence it almost fired up the ccfls?

[selldoor]

Re: Dell 1707FPt No Power

Sounds good to me- there are are few odd looking joints on the new one - the bridge rectifier and C805 and a joint just below it which I think is on the transformer - im off for an early night.

[retiredcaps]

Re: Dell 1707FPt No Power

Would those be I301, I311, & I318? I've checked 318, it's 5v input, 3.3v output.

I don't know what you are looking at, but see photo.

[selldoor]

Re: Dell 1707FPt No Power

I should have said - I am off to bed and expect you two to have it fixed when I look in tomorrow.

[maybenever]

Re: Dell 1707FPt No Power

I don't know what you are looking at, but see photo.

I'm on it, 1st thing in the morning. I gotta go away now. Will report back ASAP.
A Big THANKS

[maybenever]

Re: Dell 1707FPt No Power

Today didn't go as planned, but finally got to do some testing. On the main board, top left voltage reg, pin 1 = 5.16v pin 2 = 3.29v pin 3 = 0v. reg below that one, pin 1 = 3.29v pin 2 = 1.80v pin 3 = 0v. The top right voltage reg had 0v on all pins. But this reg checked good when the monitor would power on (one of the few times), and it had 5v input & 3.3v output. Reading were the same with or without lvds cable connected. Output voltage was stable with both boards connected, 5.16v. I removed solder & resoldered all those joints selldoor had circled and several more. Connected backlights and applied 3.1v to on pin, backlights came on full tube, for 1 sec, then off two sec, & on for 1 sec & so on. I added another AA battery to the on pin (applying 4.7v), plugged in AC, backlights came on full and stayed on, for 3 min, then went back to on 1 sec, off 2 sec cycle. While they were on for 3 min, output pins = 5.16v, steady, during the on & off cycle, voltage bounced between 4.9v & 5.3v. But the changing voltage did not match the lights on & off cycle. I could never duplicate the full on condition again.

[LDSisHere]

Re: Dell 1707FPt No Power

I think your 5V output fluctuating is due to no load being on the supply. When the back lights are on, the supply has a load so the voltage is stable, when they go off it has no load so it becomes unstable. If the fluctuating 5V is bothering you, try connecting a 100 ohm resistor between it and ground and see if it stabilizes. I would also try driving the back lights on with the supply voltage using a 100 ohm resistor between the 5V and "ON" pin, opposed to an external voltage source if that is what you are using.

When the CCFL's were on for three minutes did any one of the four bulbs flicker or dim before the other three just before it went out?

It may help if you took a picture of your test while it is in progress.

[maybenever]

Re: Dell 1707FPt No Power

When the CCFL's were on for three minutes did any one of the four bulbs flicker or dim before the other three just before it went out?

It may help if you took a picture of your test while it is in progress.

I didn't notice any flickering or dimming before they went out. I can make some pictures.
Thanks