dell E173Fpf

[mypc2007]

Hello,

I have Dell LCD monitor model E173Fpf with the following problems:

no picture and no green light. I opened the monitor and saw no components in the inverter/power supply board burnt. Any body has similar case?
Which components should i check?

Thanks
Rick

[Krankshaft]

Re: dell E173Fpf

Check out the supply in this order.

Line fuse (Continuity Check)

Check for open startup resistors (Ohms Resistor Check)

Line Rectifier (Diode Check)

Line Filter Capacitor (Ohms Resistor Check The Cap Should Charge Up)

Switching Mosfet (Diode Check For Shorted Junctions) also check for input voltage at the mosfet (DC).

Output Rectifiers (Diode Check)

If they all check out then I would check for drive voltage at the gate of the switching FET this is best done with a scope. If there is no drive voltage check for start voltage at the PWM. If there is drive voltage for a moment either the PWM protection circuits are kicking in or the PWM is shot.

If the start up resistors are fine there should be start voltage and most likely the PWM IC is shot. The one for the low voltage supply not the inverter.

The fact that you aren't getting a green light tells me that the issue is most likely on the low voltage side of the supply and the inverter circuit should be fine.

Or if this is a rare case the main board isn't sending the signal to the inverters soft start circuit to start it up but since there are no signs of burnt components lets dismiss that.

[kc8adu]

Re: dell E173Fpf

every 173 i have seen had very visible blown caps in the psu.

[mypc2007]

Re: dell E173Fpf

I checked

the line fuse F850 - OK
line rectifier D850 OK
capacitor C854 OK
D854 OK
MOSFET Q850 looks ok, no sign of burnt or cracked
I check the diodes, nothing shorted or open.
i also check resistors, nothing shorted or open
Cap(s) are ok nothing looks blown up

Which one is the PWM IC? how to check it?
What else could be the problem?
Also I have the power supply picture here

Thanks
Rick

[Krankshaft]

Re: dell E173Fpf

Thanks for the PIC by the looks of it unless U851 is the PWM IC it is on the underside of the board as a Surface Mount Component.

To find out which one it is simply take the number off the suspected IC and go to http://www.alldatasheet.com and get a datasheet for it. The datasheet will tell you which pin does what measure the voltage pin with the supply on. If the voltage is normal check the drive pin if the voltage is below normal the IC could be shot. The drive voltage will tell all.

There will be two PWM ICs down there though one near the inverter circuitry it will be called a Dual PWM since it must drive 2 CCFL circuits you want to test out the other PWM IC.

Also check the OPTO isolator that 4 pin through hole IC next to the transformer on the top of the board with the diode checker. Measure both groups of two pins separately if you get a reading in one direction switch the probes if you don't get a reading its fine.

Sorry I misread your post before no green light means that your issue lies in the main power supply not the inverter supply.

[Krankshaft]

Re: dell E173Fpf

The best way to check the PWM is by monitoring the drive voltage with an Oscilloscope thats the main reason why failures like this are so hard to pinpoint.

It requires alot of probing on the board checking components leading away from the PWM and circuit tracing to find out where the "traffic accident" happened and the current is being blocked.

Just FYI if you want to spare yourself this trouble I found a site selling a new board for $40 bucks check it out. If you feel your monitor is worth it this is a good price.

http://www.lcdrepair.us/e173fpf-logic.html

If you want to keep working on this board though keep posting.

[somtam]

Re: dell E173Fpf

i have the same problem, i have oc r856,r861 o/c, q850 s/c, r859 o/c, c857 replaced as a matter of caution. o/c......r856 is surface mount and burnt so i can not read the value. any help on this would appreciated

Hello,

I have Dell LCD monitor model E173Fpf with the following problems:

no picture and no green light. I opened the monitor and saw no components in the inverter/power supply board burnt. Any body has similar case?
Which components should i check?

Thanks
Rick

[Bobdee]

Re: dell E173Fpf

i have the same problem, i have oc r856,r861 o/c, q850 s/c, r859 o/c, c857 replaced as a matter of caution. o/c......r856 is surface mount and burnt so i can not read the value. any help on this would appreciated

Hello Somtam
Welcome to Forum
R856 = value 15R0
I am not sure what that works out in OHMs but if you cant work it out I am sure another member will help, just ask
bob

[Bobdee]

Re: dell E173Fpf

i have the same problem, i have oc r856,r861 o/c, q850 s/c, r859 o/c, c857 replaced as a matter of caution. o/c......r856 is surface mount and burnt so i can not read the value. any help on this would appreciated

Just checked on this Link
http://www.electronicrepairguide.com...stor-code.html

To me I make it 15 ohm, (if I am right that is)