Re: Dell 2407WFPb Monitor - Bad Cap
balkeep,
Your failure mode is similar to most other's here. The corrosion of C605 terminal causes it to disconnect. It is this disconnection that causes a cascading failure of circuit components. You managed to achieve that with a bad solder joint.
R670 is 0.22 Ohm, 1 Watt.
Whether IC651 can have 42 Ohms between some pins, I can't recall; it's possible. Check your Q651 with an ohmmeter, D to S. If it's short, assume that both IC's are toast as well.
pkanar
Member
Last Activity: 10-04-2023, 09:44 AM
Joined: 05-31-2013
Location: Toronto, Ontario
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Re: Dell 2407WFPb Monitor - Bad Cap
Schorsch87, take a look at the circuit diagram, post 387, page 20. The only way R603 would get fried is if the PWM module (IC601) has failed and became shorted pin 8 to pin 4. This has been occasionally reported here (e.g. post 384). If you are changing IC601, might as well change the other IC (651, the PFC). And make sure you have good resistance across Q651 (measure from D down to S).Leave a comment:
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Re: Solved: Samsung 204T LED blink, chirp, unresponsive controls
Yeah, I did recap the whole PSU, although the old Samxons were looking great and doing their job just fine.Leave a comment:
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Re: Samsung SyncMaster 204T
I can see that my 2 cents are not timely, but your symptoms are similar to [URL="https://www.badcaps.net/forum/showthread.php?p=568539"]mine[/URL]. It was the scaler card.Re: Samsung SyncMaster 204T
I can see that my 2 cents are not timely, but your symptoms are similar to [URL="https://www.badcaps.net/forum/showthread.php?p=568539"]mine[/URL]. It was the scaler card.Re: Samsung SyncMaster 204T
I can see that my 2 cents are not timely, but your symptoms are similar to [URL="https://www.badcaps.net/forum/showthread.php?p=568539"]mine[/URL].Leave a comment:
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Solved: Samsung 204T LED blink, chirp, unresponsive controls
I am posting my repair notes in the hope they may save someone else the trouble. Based on searching the web, my issue seems rather uncommon.
A 9-year old Samsung Syncmaster 204T stopped working around 2015-03-26. Increasing audible noise from its internal power supply was noticed in the weeks prior to failure. Then, one day, the bezel buttons would no longer respond, and neither the backlight nor the pixel grid would function. The green LED blinked every 0.54sec with a very brief (barely noticeable) off time. This is quite different from the blink pattern that means "no video... -
Re: Dell 2407WFPb Monitor - Bad Cap
@Andrew_LB: when I repaired mine, I would have preferred to buy a full new power supply board, and update the C605 on that. But at the time, there weren't any for sale on Taobao or eBay. Now there are, and they look like exact OEM clones. I ended up doing it the hard way: swapping circuit elements. It worked, but not worth the savings.
If you had read through this thread in more detail, you would have saved that new fuse. When the big cap dies, it always takes out one or both IC's, and more.
So, what blew? Did the C605...Last edited by pkanar; 03-15-2014, 02:57 PM.Leave a comment:
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Re: Dell 2407WFPb Monitor - Bad Cap
I don't have a 2405, or have the 2407 board handy, but looking at the picture (page 5 of this thread), they look like Schottky rectifiers/diodes in TO220FP package (common cathode on middle pin). The 5 capacitors are 470μF, 35V, 105°C (Elite EJ series)....Leave a comment:
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Re: Dell 2407WFPb Monitor - Bad Cap
All failures of the big cap seem to be the same: no evidence of leaking, but corrosion and eventual disconnection where + terminal enters the body.Leave a comment:
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Re: Dell 2407WFPb Monitor - Bad Cap
Q654: 2N3906S by KEC (PNP transistor 40V, 350mW, in SOT-23 package)
IC651: L6561 by ST Micro (power factor corrector, in SO8 package, can also use L6562)
C605 is 450VLeave a comment:
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Re: Dell 2407WFPb Monitor - Bad Cap
Just got a test report that my repair of the power board was a success.
All parts were from Mouser, with substitutions done as follows:
Q651: 2SK3502 -> STF16NK60Z (14A in a plastic package)
IC601: NCP1200A -> NCP1200 (60kHz)
IC651: L6561 -> L6562
The full Mouser part list was:
667-EET-ED2W121BA
511-STF16NK60Z
863-NCP1200D60R2G
511-L6562D
576-0215004.MXEP
756-W21-R22JILeave a comment:
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Re: Dell 2407WFPb Monitor - Bad Cap
The consensus here is that C605 is the origin of this failure. Check the ripple current spec on the replacement; it should be at least as high as the OEM, which was 740mA @ 120Hz. Also, my impression (from reading this thread) is that the PFC chip usually fails together with R669, but sometimes does not fail, however the PWM chip (IC601) has to be replaced every time, even though the measurements do not pick up anything obviously wrong with it.
The 15V Zener regulates the rail that supplies both IC's. If yours is toast, replacing...Last edited by pkanar; 07-04-2013, 07:23 PM.Leave a comment:
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Re: Dell 2407WFPb Monitor - Bad Cap
@nothin: The voltage and capacitance are on the bottom side. It will be the same as everyone else's (120μF, 450V). Insert a blade under it and gently cut the caulk from the board, to reveal its spec.
Beware that the repair will not be as simple as replacing C605. The Q651 MOSFET is almost certainly blown (measure it with an ohmmeter to convince yourself). The 2 microchips on the back likely need replacing, too.
There are fixes, and the answers are all in this thread, but a successful repair will require you to undertake...Leave a comment:
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Re: Dell 2407WFPb Monitor - Bad Cap
It does have PFC; needs 450V or higher (and 500V will be even harder to find).Leave a comment:
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Re: Dell 2407WFPb Monitor - Bad Cap
@macjedimatt: If you are doing the standard bypass surgery described in post 151 above, then you were correct that T601 is on the high-voltage side of the black line (only pins 9 and 10 are on the low-voltage side, but they are on the other side of the barrier diodes from the +19V rail you are hooking up. So, there should be no current flowing through T601 after the bypass, even if you have shorted the coil between pins 7-8 and 9-10. It should work. If it doesn't, there must be another cause. Are you by any chance connecting the +19V supply to...Last edited by pkanar; 06-16-2013, 03:22 PM.Leave a comment:
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Re: Dell 2407WFPb Monitor - Bad Cap
@macjedimatt: You are reporting what appears to be a new mode of failure. May I ask on what evidence do you conclude that T601 is damaged? And there is no corrosion where the + terminal enters the body of C605?Leave a comment:
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Re: Dell 2407WFPb Monitor - Bad Cap
@BastiaanNaber: You have a third option, search for 4H.L2K02.A01 on Taobao and buy a working power board through a reship agent such as Taobaofocus. You would still want to replace the C605 on that, even if it were brand-new.Leave a comment:
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Re: Dell 2407WFPb Monitor - Bad Cap
@BastiaanNaber: Your failure mode is typical. C605 disconnects, takes out Q651, R670, F601 and a number of other things which vary from case to case, including IC651, IC601, R669, ZD601, Q602. There have been quite a few successful component replacements, all involving replacement of IC's. I personally decided against doing the bypass, as I was not sure where to find an external 19V, 110W power supply offering the accuracy of voltage regulation comparable this board, low noise, low heat, and PFC. But, in principle, if you have such a supply,...Leave a comment:
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Re: Dell 2407WFPb Monitor - Bad Cap
@grglj: If R603 is overheating, your NCP1200 is internally damaged at the dynamic self-supply stage. What is the resistance measured from pin 8 down to pin 4?
How it was damaged, I cannot guess. Did you overheat it while soldering? That would be the easy possibility.Leave a comment:
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Re: Dell 2407WFPb Monitor - Bad Cap
Since I never found a decent circuit diagram, I am posting what I drew after tracing my board. Just added a sprinkling of component specs, and voila -- an unofficial repair manual, for everyone's reference!...Leave a comment:
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