Dell 2407WFPb Monitor - Bad Cap

[pkanar]

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 the T601 side of the barrier diodes?

[Venomhatch]

Re: Dell 2407WFPb Monitor - Bad Cap

After fixing the Main big Cap, replaced the fuse with same amperage one. Plugged it in. Book IC651 blows a section of the top of it and that is gone now. I just need to find a new Power Board. Any ideas where to find one? I have tried eBay and local CL. Ohh and I have the 2405FPW

[macjedimatt]

Re: Dell 2407WFPb Monitor - Bad Cap

Hmm.. Ok that is good to know. I did this one the same way I did the other two I have done and they both work fine. One has been running everyday for over a year. I noticed that the PA-6 power supply cuts out when I connect the power board to the main board. The main board is fine. I tested with parts from one of the others.

It is good to know I didn't kill the board! I'll have to do some more testing. It could be the particular PA-6 I'm using. I noticed the markings on it are different from the others. Does anyone have a pin out of the main board power connector so I can check the voltages without having to dismantle one of the other 2407s I just put back together?

Thanks!!

[lexwalker]

Re: Dell 2407WFPb Monitor - Bad Cap

It is coming from the edges of the top leaking inwards to the middle. I also thought it was just marker, and it isn't bulging. But I also never have seen marker look like a powderish substance.

Most likely red marker pen, seen plenty of those. Most often they would use either green or blue instead of red. When in doubt, simply replace them.

My monitor also failed, I tried using the powersupply trick with a Dell PA-9 adapter. The power adaptor's light goes out when I connect power to it. It looks like the transformer(?) near the top of the board is damaged. The markings under the heat pad are: 1J.20289.001 LTSJ 0621. Anyone know where I can get a replacement? I tried searching digikey but there are way too many options.

No. This was the same failure. After successfully fixing 2 of these, for some reason I thought it would be a good idea to cut the small wires on it. I thought it was connecting to the AC side of the board. As soon as I did it, I realized what that part was for The damage is a little beyond what I can manage to repair safely. It doesn't look like something I can find easily without more information, which I haven't been able to get. I suppose it is just as well. This panel has a scratch on it and the stand is missing.

Before or after the barrier/schottky rectifiers/diodes? Usually should be after the rectifiers as they would block the DC back to the transformer, unless one of the rectifiers/diodes is shorted (or had breakdown at certain voltage threshold). I usually use a bench power supply to test first.

[BastiaanNaber]

Re: Dell 2407WFPb Monitor - Bad Cap

I'm trying to source the parts I hope are damaged. I'm having a hard time finding the Q651 and the big cap (120UF 450V) in stores around Schiphol, the Netherlands. I have looked in this thread where Farnell and Digi-Key are mentioned. Digi-Key wants 18 euro (more than $20) for shipping and Farnell won't ship to consumers.

Any descent online suppliers? I'm willing to pay something but 18 euro is a bit steep for a 2 euro component I think.

[lexwalker]

Re: Dell 2407WFPb Monitor - Bad Cap

I'm trying to source the parts I hope are damaged. I'm having a hard time finding the Q651 and the big cap (120UF 450V) in stores around Schiphol, the Netherlands. I have looked in this thread where Farnell and Digi-Key are mentioned. Digi-Key wants 18 euro (more than $20) for shipping and Farnell won't ship to consumers.

Any descent online suppliers? I'm willing to pay something but 18 euro is a bit steep for a 2 euro component I think.

If can't find 450V capacitors, then can go for higher 500V ones. If this monitor does not have PFC then can use lower 400V ones as well (which is the voltage rating found on most AC-to-DC adaptors with the same topology). If can't find 120uF then go for 150uF or 180uF. Usually I get mine from RS Components, Farnell or Mouser. Sometimes I use eBay. Plenty of those 120uF 450V on eBay though, and cheaper too.

[pkanar]

Re: Dell 2407WFPb Monitor - Bad Cap

It does have PFC; needs 450V or higher (and 500V will be even harder to find).

[Venomhatch]

Re: Dell 2407WFPb Monitor - Bad Cap

Ok so I am thinking if I can use this:



To do the job of my PSU Board? I dont need the audio to work just the video portion.
If it is possible I guess I would need to know if anyone can tell me what both of the harnesses need voltage in these pics?:




I am thinking this could work if all that PSU board does is distribute power. But I would need to make sure everyone gets the right voltage they need.

[budm]

Re: Dell 2407WFPb Monitor - Bad Cap

That power supply is only 40 Watts, typical power consumption without Audio and USB is 57 Watts, max is 110 Watts. So the power supply should be at least 20% higher power capacity than 57 Watts MINIMUM.
https://cdn.badcaps-static.com/pdfs/...0a5c54d930.pdf
You can also see the in-rush current rating in the spec sheet.

[Mattylad]

Re: Dell 2407WFPb Monitor - Bad Cap

Cheers for the PSU fix - works a treat.

[macjedimatt]

Re: Dell 2407WFPb Monitor - Bad Cap

For those of you keeping track, I figured out what was wrong with it. The Dell PA-6 power adaptor I was using just couldn't handle it. The markings on it are very different from the other two I'm using so maybe this one just isn't made as well

I switched it out with a PA-9 and it works great. I also found a base for it This makes three of these monitors I've fixed now. I have two using the PA-6 which is a 70W powersupply and one using a PA-9 which is 90W.

[nothin]

Re: Dell 2407WFPb Monitor - Bad Cap

Sorry if this has already been covered, I scanned through this thread and did some googlin, but it's hard to absorb information when post #9 in a massive thread is a picture perfect image of my leaking cap, but with different markings

I'm an Aussie (so our sparks come out at 240V) and one of my three aged but still fantastic 2407WFP's turned itself off while in standby the other night and now refuses to power on.

Here's the only obvious sign of damage (from comments in this thread I see there may be a lot of caps to be suss at, but this one made it pretty clear it's unhappy):



While I have the most basic understanding of capacitor specs, the lack of values for farads and volts on this one leaves me stupefied. Would one of you find capacitor wizards be able to point me in the direction of a suitable spec for replacement?

[pkanar]

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 a more serious study than what you have done so far.

[nothin]

Re: Dell 2407WFPb Monitor - Bad Cap

the answers are all in this thread

OK Cheers. I'll set aside some time to read all the way through

[nothin]

Re: Dell 2407WFPb Monitor - Bad Cap

So I've confirmed the following are dead:

C605 - 120uf 450V 105C
F601 - 4A, 20mm, antisurge ceramic fuse (T4A H)
Q651 - STP10NK60ZFP, Zener protected N-channel MOSFET, TO-220, FEC code 993-551
ZD601 - 15V 0.5W Zener diode
R670 - 0.22 ohm

Is R670 a 1/2W?

IC651 - L6561D - physically appears ok, my multi doesn't have a capacitance check, are there any other test for this one?

[lexwalker]

Re: Dell 2407WFPb Monitor - Bad Cap

Q651 - STP10NK60ZFP, Zener protected N-channel MOSFET, TO-220, FEC code 993-551

Check surrounding components linked to this MOSFET, especially trace connections from the gate to the PWM I.C for possible failed components....

R670 - 0.22 ohm

Is R670 a 1/2W?

This one sounds like Rsense (ie. resistor for current sensing). That one is usually at least 2W or higher. Recommended replacement would be wirewound type resistor, rather than carbon film. Also trace the connections from this Rsense as well for any other failed components.

IC651 - L6561D - physically appears ok, my multi doesn't have a capacitance check, are there any other test for this one?

Not sure if this power factor correction I.C is spoiled, though in my opinion usually they don't usually spoil easily. In your case, I could be wrong though...

[jetadm123]

Re: Dell 2407WFPb Monitor - Bad Cap

IC651 - L6561D - physically appears ok, my multi doesn't have a capacitance check, are there any other test for this one?

You really can't use a capacitance function to check this chip. You can try a quick test by setting your meter to 1K resistance setting and checking for a short across the Vcc and ground pins.

If you're going to order all your parts from one source, go ahead and order the L6561D anyway, since it's a low cost chip.

[nothin]

Re: Dell 2407WFPb Monitor - Bad Cap

You really can't use a capacitance function to check this chip. You can try a quick test by setting your meter to 1K resistance setting and checking for a short across the Vcc and ground pins.

I think there was a post earlier here where a bloke had deemed it faulty as a connected cap was giving incorrect readings when on the board, but checked ok individually, though I may have mixed this up with another IC anyway

If you're going to order all your parts from one source, go ahead and order the L6561D anyway, since it's a low cost chip.

Makes sense - I've got 3 of these monitors, so was probably gonna order some extars anyway. On this topic, is there a consensus on which component or components actually trigger this fault? I wouldn't mind replacing these on the other two monitors, since they're of about the same age. And also, does anyone have recommendations for somewhere that ships to AU that would have all these components available? Most of our local electronics retailers carry a pretty limited range of stock...

[pkanar]

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 both IC's is prudent. That PFC chip did drive the power MOSFET to its death. Now, the PFC cannot see the ripple current that hits the circuit after C605 disconnects, except on pins 1 and 8. And I am guessing what actually happened is that it was fed with too many volts on pin 8.

[pkanar]

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-R22JI