Dell E172FPb

[retiredcaps]

Re: Dell E172FPb

any advice still?

Post some pics so we can suggest test points. There could be multiple revisions of the power board inside a Dell.

[ratdude747]

Re: Dell E172FPb

resoldered all the transformers... the soldering looked shoddy...

i put it back together most of the way and tesed it. no lamps, blocks on screen, blinking green power light.

I opened it up again and found a solder bridge on one of the CFCL transformers. I fixed that and verified that it was the only bridge (that was on two normally disconnected pins). still gives me the same symptoms...

any advice still? i hope i did not blow something... no smoke, noises, or smells.

[smason]

Re: Dell E172FPb

Hey, who let Rat in here?

Welcome to the wonderful world of LCD repair.
Definitely check for shorted transistors, transformer soldering, resistance (if you have a ring tester, use it) and
probably re-cap if the transformers are ok.

[alexanna]

Re: Dell E172FPb

my first lcd to fix...

symptoms: powers on normally for 1 sec, then no picture. green power light stays on. a quick power cycle make it work for another second.

no VISIBLY bad caps.. but a mix of lelons and elite make me wonder.

no odd noises that i remember

any advice other than a recap? places to check?

edit- slight heat browning in one of the 2 cfcl inverter areas. seems centered around a transformer, diode, and PI coil (i think) area. It also has little jamicon caps.

Something I have learned on these monitors. And I am assuming there are 4 inverter transformers?
The symptoms you describe sounds like a shorted or open transistor for on one of the inverter transformers.
Unplug all the CCFLs and then plug one back in at a time [only have one CCFL plugged in at a time], power on the monitor, do you see a flash of light with each CCFL?I really suspect 2 of the transformers will not light the CCFL,Check the transistors associated with that transformer for a shorted or open condition.
And as is recommended resolder the transformers.

[retiredcaps]

Re: Dell E172FPb

I forgot to add that these Benq style boards have really poor soldering on the inverter transformers. You must resolder all the inverter transformer pins.

[retiredcaps]

Re: Dell E172FPb

my first lcd to fix...

"2 seconds to black" can be

1) bad caps
2) bad ccfls or bad wiring
3) bad inverter transformer
4) bad inverter sense circuitry

1, 2, and 3 are documented at starting with post 13 and 14.

https://www.badcaps.net/forum/showthread.php?t=10419

Pictures always help since it possible that Dell used a different power board and kept the same model number.

[ratdude747]

my first lcd to fix...

symptoms: powers on normally for 1 sec, then no picture. green power light stays on. a quick power cycle make it work for another second.

no VISIBLY bad caps.. but a mix of lelons and elite make me wonder.

no odd noises that i remember

any advice other than a recap? places to check?

edit- slight heat browning in one of the 2 cfcl inverter areas. seems centered around a transformer, diode, and PI coil (i think) area. It also has little jamicon caps.