Dell XPS 720 H2C

[compirate]

I've got a Dell XPS 720 H2C where the motherboard doesn't even post, not even one beep. From what I've read these boards are trouble, hoping just the caps. None show any visible sign of trouble.

Here's the list of what it has:

27- 220uF 16v 6.3x11 Rubycon ZLH A0734/5 .22 540
4 - 680uF 16v 10x12.5 Chemicon KZG 7(T)9X 0.026 1540
5 - 2200uF 6.3v 10x20 Chemicon KZJ 7(7)9Q .011 2920
4 - 1800uF 6.3v 8x21 Panasonic FL 79IIEA .016 1870
3 - 560uF 4v 8x12.5 Sanyo 732SEPC5604
6 - 4.7uF 50v 5x12 Rubycon NXA bi-polar A0734
1 - 330uF 16v 10x13 Chemicon C73033016V
10- 560uF 4v 8x8 Chemicon C78L5604V
1 - little teeny tiny cramped in hidden one

From reading here, I should replace anything 680 and higher.

I've been able to find compatible replacements (I think) for most:
2200uF - UHN0J222MPD
1800uF - UHM0J182MPD6
680uF - UHM1C681MPD

The 680's aren't available anywhere that I can find right now so my question is (it's about time he got to it!) how far out of spec can you go? I realize lower ohm, higher ripple is good but:
Mine Badcaps Store
KZG HZ
.026 .012
1540 2280

In the attached picture, at the bottom where it says '680uF', that connector is for the cooling pump, the connector to the right is the card fan. The connector on the left edge between the 4 220uf is the hard drive fan connector.

Oops, missed one! North end of east ram connectors, 220uF

[momaka]

Re: Dell XPS 720 H2C

The 680's aren't available anywhere that I can find right now so my question is (it's about time he got to it!) how far out of spec can you go?

You can go as much out of spec as the height and width of each capacitor spot allows. In my experience, even 2x to 3x the capacitance was never a problem, and just about every motherboard and video card I have recapped I did so with "non-standard" replacement caps (i.e. whatever I had on hand, which is usually large caps from Xbox 360s). If you use Nichicon HM, HN, and HZ with that logic, you will more than meet the ESR and ripple current requirements of the circuit.
Another alternative would be to use polymer caps. 470 uF @ 16V might do just fine. I don't see any other large 16V caps on that motherboard, so I assume those 680uF 16V KZGs are for the CPU VRM high side (and it appears so from the picture you posted). On the power supply, what are the colors of the wires going to that connector that pluggs in at the bottom-right of the motherboard?

[compirate]

Re: Dell XPS 720 H2C

Thank you for the reply!

The power connectors are unique to Dells :

The power supply is either a 750W or 1000W
Upper left connector, left upper pin is #24, right #12:
1 +3.3 VDC Orange
2 +3.3 VDC/SE Orange
3 COM Black
4 +5 VDC Red
5 COM Black
6 +5 VDC Red
7 COM Black
8 POK Gray
9 +5 VFP Purple
10 +12 VD DC/SE Yellow/White
11 +12 VD DC Yellow/White
12 +3.3 VDC Orange
13 +3.3 VDC Orange
14 -12 VDC Blue
15 COM Black
16 PS_ON Green
17 COM Black
18 COM Black
19 COM Black
20 N/C
21 +5 VDC/SE Red
22 +5 VDC Red
23 +5 VDC Red
24 COM Black


Lower right connector, upper left #20, right #10
1 +12 VC DC Blue/White
2 +12 VC DC Blue/White
3 COM Black
4 COM Black
5 +12 VA DC/SE Yellow
6 +12 VA DC Yellow
7 COM Black
8 COM Black
9 +12 VB DC/SE White
10 +12 VB DC White
11 +12 VC DC/SE Blue/White
12 COM Black
13 COM Black
14 COM Black
15 +12 VA DC Yellow
16 COM Black
17 COM Black
18 COM Black
19 +12 VB DC White
20 NC

Attached is a line drawing of the motherboard.

[momaka]

Re: Dell XPS 720 H2C

So it looks like the lower connector is indeed for powering the CPU, since it has only 12V rails going to it. In that case, those 680 uF 16V KZGs should be for the CPU VRM high side. Most regular motherboards usually employ four 1000-1500 uF caps for that. So if you can't find suitable 680 uF caps, you can go with 820 uF, 1000 uF, 1200 uF, or 1500 uF - that is, as long as cap height is not an issues, because those larger capacity caps will also be bigger. Another tip I'll give you here is that on Mouser (and possibly also Digikey), less popular capacities like 1200 uF can sometimes be cheaper than both 820 uF and 1000 uF caps.

Here are a few choices that could work for your 16V 680 uF KZG:
(perfect match)
https://www.badcaps.net/store/produc...roducts_id=178
(1000 uF)
https://www.badcaps.net/store/produc...roducts_id=174
(1500 uF)
https://www.badcaps.net/store/produc...roducts_id=139
(820 uF polymers)
https://www.badcaps.net/store/produc...roducts_id=135

[compirate]

Re: Dell XPS 720 H2C

Sorry for the delay, thanks for the reply. Now to order the parts and cross my fingers!

[compirate]

Re: Dell XPS 720 H2C

Yea! Parts finally showed up (1/23). Came from Carrollton, Tx to Capitol Heights, Md to Lexington Park, Md, back to Capitol Heights then to me! Only an extra 180 miles trip for them Now to clear off this workbench and fire up the ol' soldering iron!

[compirate]

Re: Dell XPS 720 H2C

Well that didn't do it

still stuck posting at "initializing power management" (post error 10h), if i read this post code card correctly - shows last successful code). Wish I knew how to fix that

[momaka]

Re: Dell XPS 720 H2C

Sorry to hear it didn't work out. :\
But that's electronics repair for you - sometimes it works and other times it doesn't and you have to troubleshoot it more.

If you want to troubleshoot it more, I guess the next item to check would be all of the power rails. Besides the 4 toroidal coils next to the CPU socket, there are three more - one by the RAM modules (lower-left of your picture), another by the SATA ports, and one more next to the Northbridge (?) right in the center of the picture above. Those coils indicate buck-type power rails and they are the most likely to have a problem if the board had bad caps. You can also see two TO-252 MOSFETs next to each coil.

If you have a multimeter, the easiest way to check these rails is to measure the voltage they are outputting. One of the two MOSFETs next to each coil will have its tab connected to that power rail (but not both). For this reason, check the voltage on the tabs of both MOSFETs for each rail, and post what results you get here.

The coil next to the RAM slots is likely going to be for the RAM, so probably should see 1.8V. The coil next to the SATA slots could be for the Northbridge or the Southbridge, so I can't say exactly what voltage to expect, but we can figure out if its right or not by knowing what chipsets the motherboard uses and checking those chipets' datasheets. Finally, the coil in the center of the picture next to the Northbridge is likely for the Northbridge only. Probably around 1 to 1.2V.

[c_hegge]

Re: Dell XPS 720 H2C

These boards do have nvidia bumpgate chipsets. That's also a possibility.

[bcgrogbc]

Re: Dell XPS 720 H2C

So were the UHM0J182MPD6 a good replacement for the 1800uF 6.3v 8x21 Panasonic FL?

[momaka]

Re: Dell XPS 720 H2C

^ Should be.
HM and FL are about equivalent.

[c_hegge]

Re: Dell XPS 720 H2C

Yup. I don't think the caps were ever the problem. It's usually the chipsets that go wrong with these boards, as there are known manufacturing defects with them.