power supply component problem

[nickBcap]

Hi, a faulty Dell XPS720 PC.
The power supply powers the motherboard on and gives a green motherboard LED but the motherboard is a no boot and no bios, just a black screen and components are A ok.
No beeps, no PC LEDs light up.
The capacitors in the PSU and on the motherboard all look ok.
I checked all the PSU solder joints and may have found one or two cold solder joints so re soldered them.
When I was checking the PSU solder points I saw what seemed like two messy solder joints. I removed the solder from one and found a white board marking under where the solder was and it is a boundary line for solder.
In the two photos the first shows almost all the white line between the two points that were soldered. The second photo shows the second place where I am quite sure same kind of components are used and a same white line exists beneath the solder - but with this second soldered point I am having an especially hard time removing the old solder.
Can anyone tell me whether the two points in question that have the white line beneath the solder(100% sure there is a white line beneath the second) should have been soldered?
It seems logical that if one of the two soldered points of two same components is soldered and the other two same components is not soldered then there may be a mistake. The odd soldering appearance that attracted me to these two same components soldered points makes me think there may be a mistake, maybe someone did this aftermarket.
I do not understand why the motherboard will not boot but I am prepared to replace the larger motherboard capacitors.
Also, I am not sure if I should replace any PSU or motherboard capacitors at this point either but seems a logical step for repairing and I may have found a PSU dell connector pinout for testing the power supply, which is an exciting step for me to have made I am pleased to say.
Not sure why the pictures are out of focus.

[Pentium4]

Re: power supply component problem

You don't want to bridge the two joints like that if they weren't like that to begin with, they're separated for a reason. There was probably an option to install an additional component on that section of the board, but the manufacturer doesn't always install every component if they aren't necessary for the boards intended application. Could you post some overhead pictures of the board and power supply?

[nickBcap]

Re: power supply component problem

Just a quick reply then I will post the pictures of the power boards.
I like your "Buy quality, and you only cry once" I begin to comply.
Cheap components are just an opportunity to learn...howabout that.
Anyhow, the first of the two sets of the two components that were soldered together in the photos, was soldered to begin with. I wanted to resolder a few extra solder points and arrived at the two first of the two sets of same components, and noticed the solder removed from the components was not the first original solder for the components. The two components had each of their original solder soldering them to the power board. After seeing the white line I recalled the reason for the white lines. Btw, this is a Revision A05 power supply. Dell P/N: HPW7508F3.
One question: how do I test this power supply? Is it enough to power on the power supply with a load then use a digital multi meter and probe any black (earth), and any white yellow red blue etcetera wire connections? I do have a cheaper PSU tester but I dont this works correctly with this proprietory Dell PSU.

[nickBcap]

Re: power supply component problem

< but not; it looks like a dancing happy sheep and I am a Christian
Here is the PSU power boards and info on the PSU label.

[c_hegge]

Re: power supply component problem

We prefer photobucket or other 3rd party image hosts not to be used here. I have attached the pictures locally for you.

Incidentally, I have the exact same PSU here in my stash. Those things are built like tanks.

EDIT: I have had a look at my unit, and I can confirm that the joints are indeed bridged. You can see it if you look very carefully, and my DMM confirms that they are connected.

[nickBcap]

Re: power supply component problem

ok, thank you. I will solder those components.
I tested the motherboard capacitors and got many different readings for capacitors of the same ratings. I grounded the multi meter terminals after each reading so think I got accurate readings.
All the 716/SEPC/ 560(I think the 560 indicates uF correctly)/4 meaning 560uF 4V imo..., on the motherboard around CPU socket all gave something like 1950uF readings which is a bit confusing seeing all reading way over the 560uF rating.
There was not many same rated capacitors on the motherboard that gave equal readings. I guess I should go ahead and replace all of them. At the least this would be the perfect solution wouldn't it?

[kc8adu]

Re: power supply component problem

those 560 are all in paralell on vcore.
sepc are sanyo polys and very unlikely to fail.

[nickBcap]

Re: power supply component problem

Why would I get the readings of 1950uF for the 560's? Is that something to do with being in parallel like Dual Channel memory perhaps?
I think I will go ahead and replace all the Rubycon capacitors on the motherboard. I have replaced capacitors on LCD monitors with good success and in Power Supplys.
I am presently searching for any recommendations for Aywun PSU repairs. I own a 650W Aywun PSU and it stopped working after a very little use. Also I suffer from a voltage drop here in my flat which I am hoping is resolved very soon. It seems the Aywun PSU's have a typical kind of problem, a weakness somewhere but I have not found it.
Thanks for posting, this is great stuff, thanks for the recommendations, I do appreciated them.
btw I just spotted a btx ad in Ebay for intel btx boards in the US for US$9.99 + something like $40 postage. Just thought they may be useful to people who may have an idle BTX case lying about. Intel E210882 D945GCZLKR LGA775 BTX New Board Sealed - Ebay.

[c_hegge]

Re: power supply component problem

You will get 1950uF if you have four caps in parallel. In reality, though, they would have to be just under 500uF each (which is still within tolerance).

What model Aywun PSU have you got? At best, Aywun PSUs are mediocre, liar-labelled units, which can't deliver the rated wattage (but might to OK at 200W or so less), and at worst, they are complete junk which can't deliver anything in spec.

[nickBcap]

Re: power supply component problem

I paid $100NZ(similar $ rate to the US$) for an Aywun Megapower 650, Model Mega Power Eco Series A1-650E. I was kind of thrilled at the low price and wanted a power supply to use for testing motherboards. I now have an Antec 700W VP700P bought for something like $120NZ.

[nickBcap]

Re: power supply component problem

btw, I have chosen; Nippon, Rubycon and Panasonic capacitors to replace all the motherboard non solid state capacitors. Because the motherboard showed a green power on LED and going by your comment the Dell HP power supplies are built like tanks, I am going to assume the power supply is ok. If the PSU is not ok I will discard this motherboard. I found a pinout to guide me in the testing of the PSU with a multi meter.