About replacement of bad capacitors of pc mainboards.

[Leung Kai-yan]

Dear friends:
What is the percentage of success of making the pc mainboards work properly again after replacing them with good capactors in the proper way? I mean the approximate one.

Thank you.

[dood]

Re: About replacement of bad capacitors of pc mainboards.

so far I've done 10 boards and have only had one that didn't work afterward, and that's because it had seriously cooked. I even replaced the caps on this old motherboard - https://www.badcaps.net/forum/showthread.php?t=1583, also had to replace the one MOSFET... I never thought it'd POST again, but i'll be damned if it didn't fire up first try!

[linuxguru]

Re: About replacement of bad capacitors of pc mainboards.

If it has no other problems, and you're skilled at rework, and the replacement caps are high-quality and of the correct values, no reason why it shouldn't be 100%.

However, if the boards are trashed/scrap boards with an unknown history of rework and/or additional faults, the recovery rate may be 0%.

In my case, it's running at about 8/10 or 80% now. I have 2 boards with other, probably unrelated , faults, which may be repairable - but I just ran out of time/patience. One is a rebadged K7SEM which loses its CMOS settings everytime. The other is a generic Slot-1 440LX board that has difficulties with Slotkets.

[willawake]

Re: About replacement of bad capacitors of pc mainboards.

reasons for failure :

- board had other issues not just badcaps
- soldering iron inadequate wattage (leads to too long heating)
- too long heating (better technique required for some holes or use better tool)
- rushing the job towards the end
- making mistakes from being tired or getting angry
- iron slips and scratches a trace or detaches an smt component (possible to repair)

best way to start is to practice recapping trash boards then do a real recapping, recap something very easy like a network switch. then move on to boards around P3 era. once experience is gained then move on to newer boards and lead-free boards where wattage of iron and technique really matter.

If boards that have other issues not badcaps are excluded and the iron is good wattage, the success rate should be almost 100%. if you fail you will understand why you failed and make sure you change your technique and/or get a better iron and not fail the same way again.

[Rainbow]

Re: About replacement of bad capacitors of pc mainboards.

My success rate is 100% for boards that have only bad caps.
I also get a lot of boards in unknown state - many of them can be fixed (mostly mechanical damage, bad caps, badly flashed BIOS, blown transistors). Many can't (blown chipset) - they end up on one "death" pile as component sources. I have also about 10 boards on "mystery" pile - they don't work at all or don't work properly and I don't know why. And about 10 boards waiting for components (usually blown VRM chips - they're hard to get).

[yanz]

Re: About replacement of bad capacitors of pc mainboards.

I've recapped 22 boards or more, only to find 1 board (ecs k7s5a) fail to work again. I'm too lazy too check that board if it's has shorted mosfet/vrm or other problems.

[kc8adu]

Re: About replacement of bad capacitors of pc mainboards.

100% here if it posts before i recap.
about 75% of boards with other damage besides the bad caps are fixable.
a lot of what i repair are for industrial apps and big business.
some of this stuff is unobtainium in its purest form.so its worth the time to fix the blown up stuff.

[Neo2_000]

Re: About replacement of bad capacitors of pc mainboards.

Testing Beforehand:
Does it boot: YES=Recap NO=Replace obvious swollen caps
Does it boot: YES=Recap NO=Probability of succes low - discard

Testing after recap:
Does it Boot: YES=further testing NO=troubleshooting
Does it Boot from boot floppy: YES=further testing NO=troubleshooting
Pass burn in test: YES=further testing NO=troubleshooting
Does it install OS ok: YES=further testing NO=troubleshooting
Does OS perform normally: YES=SUCCESS No=troubleshoting

Just had a board which passed all but after a month or two went sideways.
I judge success by longstanding flawless performance. Using this criteria, my success rate is probably 70% or better overall.

Somtimes other components may be compromised which leads to eventual failure. I have noticed that the general condition of the board provides some clue to success and will take this into consideration when deciding to recap. Sometimes a single component will fail such as the onboard LAN which is remedied with an add-on card.

Not sure how many boards I have done - somewhere around 40 I guess. The soldering iron I was using was responsible for some failures as was the shitty quality of some of the old solder originally used which made it difficult to decap. My technique has improved considerably over time with experience and I now have a proper iron - my old one was a sledgehammer!

I expect a cretain percentage of failures. Given some of the old Pentium 3 boards I work on, I think it would be unreasonable to expect perfection. I am not as skilled or experienced as some members of this forum but then again I have seen ex-factory returns subject to failure. Most of us would kill for the equipment those guys have at their disposal.