Instances where a recap board will not work

[Northeastern292]

Are there instances that even a recap will not bring a mobo back to life? Late last year I brought an old Dell Dimension 4400 from the local transfer station and even after recapping the motherboard, the unit was still non-functional.

Is there a "point of no return" with a computer motherboard where even recapping it will not fix it and it's just toast? I think I've only been able to save a few machines with bad caps, and in those cases, it was only one or two caps and the machine would still POST.

[selldoor]

Re: Instances where a recap board will not work

I have little personal experience but would guess there are lots of cases where a recap will not fix it. Diodes, voltage regulators, mosfets can all fail along with hundreds of fleapoop size resistors and capacitors, not to mention the main chips detaching. I have afew lying around I am "fixing" not sure why as they have less computing capacity than a phone

[Northeastern292]

Re: Instances where a recap board will not work

I have little personal experience but would guess there are lots of cases where a recap will not fix it. Diodes, voltage regulators, mosfets can all fail along with hundreds of fleapoop size resistors and capacitors, not to mention the main chips detaching. I have afew lying around I am "fixing" not sure why as they have less computing capacity than a phone

Guilty of the same thing.

[momaka]

Re: Instances where a recap board will not work

Yes, there have been cases of that - lots of them actually.

Sometimes when the capacitors fail, they can take out a MOSFET or a voltage regulator with them, or even an IC. I have a Shuttle motherboard that suffered this faith. Basically, as the caps for the Northbridge blew, they took out a MOSFET in the the Northbridge VRM along with the VRM controller. I suspect this killed the Northbridge since I replaced the faulty MOSFET and the controller, but the computer did not come back on. Northbridge is receiving correct voltage now, too.

I have afew lying around I am "fixing" not sure why as they have less computing capacity than a phone

Same here. Just because they don't have a lot of computing power doesn't mean it's still not fun to fix them, though .

[Northeastern292]

Re: Instances where a recap board will not work

Yes, there have been cases of that - lots of them actually.

Sometimes when the capacitors fail, they can take out a MOSFET or a voltage regulator with them, or even an IC. I have a Shuttle motherboard that suffered this faith. Basically, as the caps for the Northbridge blew, they took out a MOSFET in the the Northbridge VRM along with the VRM controller. I suspect this killed the Northbridge since I replaced the faulty MOSFET and the controller, but the computer did not come back on. Northbridge is receiving correct voltage now, too.


Same here. Just because they don't have a lot of computing power doesn't mean it's still not fun to fix them, though .

I'm figuring there were enough blown caps (5!) to take the mobo south. I replaced the caps and no one behold, turned it on and fans came on full blast, with no video. It's a six year old machine, but I still want to fix it. At least eBay has for sale some XPS 410 boards that are in the $35 range that are supposedly new (old stock), but if the CPU is also bum, I'm not sure if I'd be comfortable putting $50 into a machine that old. God only knows if the CPU also became victim to this board. It'd be nice to only have to slip a new board in and presto, everything works.

[momaka]

Re: Instances where a recap board will not work

If you recap a motherboard, and it still doesn't work, check the voltage rail on which the caps were on to see if it's at the proper voltage. If yes, check all of the major voltage rails. That means, check the following:
CPU core
Northbridge core
RAM DIMM supply
RAM standby supply
AGP (on older boards that have AGP)
any other buck or linear power VRM circuit you find

Usually, there is an intermediate VRM before RAM DIMM (normally 3.3V for boards that use DDR RAM, and 2.5 to 3.3V for boards that use DDR2 and DDR3 RAM). Same with RAM standby supply.