Dell 1703 FPS Board # 79044120 Dead no life

[sam_sam_sam]

This is a monitor that I bought at the Computer Recyclers Center where I live
for $20.00 US

[sam_sam_sam]

Re: Dell 1703 FPS Board # 79044120 Dead no life

< Please and Thanks for any help that you can give me



I have power the board with a 12 volt power supply and can get the evey thing to work but it will not power on with the power cord
I had remove the yellow tranformer when using the 12 volt power supply

I am real as what to do next


Any idea what to check next I have replaced the mosfet and still no go
The Cap near the yellow tranformer has a voltage about 160 volts DC

[PlainBill]

Re: Dell 1703 FPS Board # 79044120 Dead no life

< Please and Thanks for any help that you can give me



I have power the board with a 12 volt power supply and can get the evey thing to work but it will not power on with the power cord
I had remove the yellow tranformer when using the 12 volt power supply

I am real as what to do next


Any idea what to check next I have replaced the mosfet and still no go
The Cap near the yellow tranformer has a voltage about 160 volts DC

To repair monitors in a cost effective manner you must not arbitrarily replace components unless you have a good reason to believe they are defective.

In case of a 'Dead' problem, the first step should be to measure the output voltage of the power supply. If this is 0 volts, the second step is to measure the voltage across the large cap. 'About 160 volts' is interesting for a number of reasons. It is approximately correct, if slightly low. Is it steady, or does it vary? Are you measuring with a DMM?

If the output is 0 volts, but the voltage across the large cap is correct, the next step is to check the SMPS controller. What is the part number on U850? What is the voltage on Vcc?

PlainBill

[sam_sam_sam]

Re: Dell 1703 FPS Board # 79044120 Dead no life

Here is the Data Sheet for U850 <
Here is the Part # for U850 <..> SG5841SZ

How do check U850

I had check the Q850 which is a mofet on both boards with a meter and got two very different reading on each one so did not know which one was bad or either one was good and the cost of each one was about $2.00 each on Ebay

I check to see if the gate on Q850 had any voltage which it did about 14 volts DC

[sam_sam_sam]

Re: Dell 1703 FPS Board # 79044120 Dead no life

"About 160 volts' is interesting for a number of reasons. It is approximately correct, if slightly low. Is it steady, or does it vary? Are you measuring with a DMM?"

For most part it steady

[PlainBill]

Re: Dell 1703 FPS Board # 79044120 Dead no life

Thanks for the link to the datasheet. That saves me a bit of trouble.

Use pin 1 of U580 as ground. What are the voltages on pins 3 and 7?

PlainBill

[sam_sam_sam]

Re: Dell 1703 FPS Board # 79044120 Dead no life

PlainBill

I will give you those reading a little later on today

If I have to replace this chip what is the best way to remove the old one and solder in the new one I have not solder ( 8-Pin Small Outline Package (SOP) type before

[PlainBill]

Re: Dell 1703 FPS Board # 79044120 Dead no life

PlainBill

I will give you those reading a little later on today

If I have to replace this chip what is the best way to remove the old one and solder in the new one I have not solder ( 8-Pin Small Outline Package (SOP) type before

ChipQuik makes removal easy. Clean up the residue using solder braid. Soldering is covered in this video.

PlainBill

[mariushm]

Re: Dell 1703 FPS Board # 79044120 Dead no life

Here's another tutorial about soldering chips and smd stuff... maybe his style of explaining is easier for you : http://www.youtube.com/watch?v=b9FC9...ailpage#t=559s

I watched the three part tutorial he made and found it quite good. Basically use flux and quality solder wire...

[sam_sam_sam]

Re: Dell 1703 FPS Board # 79044120 Dead no life

PlainBill

U850 .........>

Both pin 3 and 7 have a voltage between 12 and 14.5 volts DC trying to turn on the monitor make no difference

The measurement across the large cap is a steady 166.7 volts DC

[sam_sam_sam]

Re: Dell 1703 FPS Board # 79044120 Dead no life

I made a mistake in this post it is not a E1703 it is a E1706 sorry about this

I have both model

[PlainBill]

Re: Dell 1703 FPS Board # 79044120 Dead no life

PlainBill

U850 .........>

Both pin 3 and 7 have a voltage between 12 and 14.5 volts DC trying to turn on the monitor make no difference

The measurement across the large cap is a steady 166.7 volts DC

Not nearly good enough. Let me explain. I do not have the monitor here. I cannot see what readings you are getting. If you are unwilling or unable to give me specific information, you might as well go back to changing parts at random.

Pin 3 is the startup input. It is connected to the +166 volt supply by a large value resistor. Pin 7 is Vdd - the supply voltage for the IC There is a startup cap from pin 7 to ground. When the monitor is plugged into AC power the startup cap is charged until Vdd reaches 16 volts. At that point the SMPS controller starts, and provides it's own run power.

The voltage on each pin, and the characteristics are critical. If the voltage at pin 7 is jumping around it indicate one problem. If it is steady, it indicates another. If the voltage at pin 3 is too low, it indicates something else.

PlainBill

[sam_sam_sam]

Re: Dell 1703 FPS Board # 79044120 Dead no life

"If the voltage at pin 7 is jumping around it indicate one problem." <... YES
between 12 and 14.5 volts

" If it is steady, it indicates another." <...... NO

" If the voltage at pin 3 is too low, it indicates something else." <.... The voltage is the same between 12 and 14.5 volts What should this voltage be ??

" If you are unwilling or unable to give me specific information, < ... This is NOT the case these are the reading that I am getting

" you might as well go back to changing parts at random." <........ I really do not want this way



I am trying to give you the messurement that you are asking for

Please bear with me on this thanks

[sam_sam_sam]

Re: Dell 1703 FPS Board # 79044120 Dead no life

" Pin 3 is the startup input"......> "There is a startup cap from pin 7 to ground. When the monitor is plugged into AC power the startup cap is charged until Vdd reaches 16 volts."

It never reaches 16 volts on either pin 3 or pin 7 so what do I need to need to check


I do have cap tester how ever I will need to remove the cap to test them

You need to let which ones I need to check

[PlainBill]

Re: Dell 1703 FPS Board # 79044120 Dead no life

" Pin 3 is the startup input"......> "There is a startup cap from pin 7 to ground. When the monitor is plugged into AC power the startup cap is charged until Vdd reaches 16 volts."

It never reaches 16 volts on either pin 3 or pin 7 so what do I need to need to check


I do have cap tester how ever I will need to remove the cap to test them

You need to let which ones I need to check

The key is the voltage jumping. It is likely that the startup cap is bad. Another possibility is that the SMPS controller is bad. A third possibility is that one of the outputs is shorted, but that is much less likely.

I'd suggest starting by checking the diodes on the output of the SMPS transformer. Since you got the monitor working using an external supply, we know there is no problem with a short on the load. Next, try replacing the startup cap with a known good one and seeing if that fixes the problem. If the output diodes were not shorted, and replacing the startup cap doesn't fix it, you have a bad smps controller. DigiKey doesn't carry them, but they are available on eBay.

PlainBill

[Rtech]

Re: Dell 1703 FPS Board # 79044120 Dead no life

I have only seen this Board on the Dell FPf series of Monitor, and the SMPS controller is known to fail on a regular basis,so looks like you are on the right track.

[PlainBill]

Re: Dell 1703 FPS Board # 79044120 Dead no life

I have only seen this Board on the Dell FPf series of Monitor, and the SMPS controller is known to fail on a regular basis,so looks like you are on the right track.

Unfortunately for 3sam, the controller is not available from DigiKey. Fortunately he can buy 5 for $10 (including shipping) from eBay sellers in China.

PlainBill

[Rtech]

Re: Dell 1703 FPS Board # 79044120 Dead no life

Unfortunately for 3sam, the controller is not available from DigiKey. Fortunately he can buy 5 for $10 (including shipping) from eBay sellers in China.

PlainBill

Thats where I purchase mine from,and they are used quite regularly.

[sam_sam_sam]

Re: Dell 1703 FPS Board # 79044120 Dead no life

The key is the voltage jumping. It is likely that the start-up cap is bad. Another possibility is that the SMPS controller is bad.
I'd suggest starting by checking the diodes on the output of the SMPS you have a bad smps controller. PlainBill

I found the part at Mouser 512-SG5841JSZ .....> SG5841SZ



I put it in today and it came back to LIFE the only problem now is to get a set of CLF tubes that are good to finish this repair

I can only hope .....>
___________________________________________________________

The reason I do not a good set of CLF tubes I have three monitors that have the same model # and one them the boards worked but one of the CLF was bad on the other monitor had one CLF that did not work but the other one did not and only one that both sets of CLF tube

I did not care about this at the time, because I only had ONE board that work

The Last Board has some real Problem with it one of the resistor that is real tiny rear the U850 is OPEN also there is a problem
with U851 or with U801 or with U802 it work BUT I had to use two power supplys to get it to come on BUT I do not think I want to spend the time on this board I will just CUT the invert board part off of it and use it to check CLF tube with it



PlainBill

I WANT to THANK YOU for all of your help in this matter and helping get this monitor working again I wish I could send you a