Re: Dell E172fpb
Well, that rules out bad CCFLs, then. I've repaired a couple dozen of them now, and it's quite common for one pair of transistors to go bad while the other pair is fine (for the time being). In any case, you'll want to make sure to resolder all those solder joints, to make sure they don't fail in the future....
Mohonri
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Last Activity: 06-16-2021, 05:45 AM
Joined: 05-06-2009
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Re: Dell E172fpb
Swap the CCFL cables, to ensure that both CCFL's indeed work....Leave a comment:
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Re: Dell E172fpb
Wow, I've seen a few questionable solder joints, but those are just inexcusable!...Leave a comment:
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Re: Dell E172fpb
^^ What he said--you need to also resolder the transformers. Replacing the transistors only treats the symptom. I've fixed a fair number of this model monitor, and have only seen one or two monitors with blown caps. The rest all had blown transistors due to bad solder joints on the transformers....Leave a comment:
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Re: Dell E173FPb smoking
It sounds like the overcurrent protection isn't working. The schematic for the e173fpb's inverter is largely similar to the schematic for the e172fpb's. There's a PNP transistor (sorry, forget the number) for each backlight which shuts off if there's too much current, and sometimes, these fail to a short. IIRC they are FU9024N transistors. Replace these and see if it helps.Leave a comment:
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Re: Help identify transistor from E173FPc?
While I wait for replacement parts, does anyone happen to know what voltage is on the secondary? On other Dell E17xxxx models, it's typically 12V, but I don't know whether that's the case with this particular model. I'd like to hook up 12V from another source to see whether the inverters work on their own, without the primary.Leave a comment:
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Re: Help identify transistor from E173FPc?
Yup, there's a 2A 250V fuse that went as well, I surmise because the transistor failed. Of course, I don't have confirmation yet that nothing else failed--I received the monitor in less-than-perfect condition. The PWM chip was half-desoldered, and it appears someone tried to replace a cap on the secondary...
...which, on second inspection, has been installed [i]backwards[/i]. Eesh, maybe it's a good thing the transistor failed. That could have been entertaining had I fixed everything up and fired it up...
I've...Leave a comment:
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Re: Help identify transistor from E173FPc?
Wow. Right on the money. And how the heck did you know that?
Thanks a ton.
By the way, why is the voltage rating so high? Does the the voltage really spike that high when the transistor turns off?Last edited by Mohonri; 12-23-2009, 12:38 PM.Leave a comment:
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Help identify transistor from E173FPc?
For once, I have a monitor with *good* 2SC5707's. This time, the bad transistor is the MOSFET on the primary side. I've been trying to identify it, so as to find a suitable replacement, but my google-fu is failing me. The markings on it are as follows:
ST logo
WDZ247 (the D could be an O or a 0, the Z could be a 2)
China (this one's not particularly helpful)
PBNK802 (lot/batch/date information)
FP
I can't seem to find any information on it, no matter what combination of (D|o|0)(2|z) I use. Can anyone help me ID this transistor?
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Re: Dell E172fpb again
Have you tested the inverter transistors? That's the most common failure mode I've seen. Check out [url=https://www.badcaps.net/forum/showthread.php?t=1303]this thread for more information[/url].Re: Dell E172fpb again
Have you tested the inverter transistors? That's the most common failure mode I've seen. Check out [url=https://www.badcaps.net/forum/showthread.php?t=1303]this thread for more information[/url].Re: Dell E172fpb again
Have you tested the inverter transistors? That's the most common failure mode I've seen. Check outLeave a comment:
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Re: Dell E172fpb
It's possible that one or both of the FU9024N transistors on the board have failed as well. If one of those fails to a short, the entire board shuts down. I don't recall how they are labelled on the board (and I'm 1400 miles away from mine), but they have the same package as the 2SC5707's.
Can I assume that you resoldered all the legs of the transformers when you replaced the transistors?...Leave a comment:
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Re: Dell E172fpb
Well, I'm now up to six or seven of these monitors. One of them had a failed FU9024N, but all had failed C5707 transistors. Replacing the failed transistor and resoldering the tranformers has done the trick every time.
One tip I've learned: The transistors *can* be tested in-circuit by using the "diode" setting on my multimeter. Measure from base to emitter and from base to collector. Both should be between 0.5V to 1.0V. Failed transistors show a short.
Also, a hot iron is important. If your iron isn't hot enough, the traces...Leave a comment:
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Re: Dell E172fpb
I had the same issue as everyone else--monitor turns on, then starts flashing every second or so.
First, I replaced the (single) bad transistor. The monitor worked fine for about a week, then exhibited the same symptoms.
The second time, I replaced the newly bad transistor, and resoldered all the joints on the transformers. Since then (going on four weeks now), all appears to be well.
So chalk up another vote for "Resolder the transformer legs".Leave a comment:
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