Motherboard capacitors

[edavid]

Cleaning is part pride and partly practical. Depending on the flux used, the gunky residue can be chemically active and cause corrosion. It can also be somewhat conductive. In a high-speed board, it can cause problems. If not today, possibly later. Possibly never. Why not clean it and never worry about it?

The board has been working for 10 years, so whatever flux is on there isn't a problem.

The OP is not going to be using anything other than rosin flux, also not a problem.

There's just no reason to mess with it.

[jimdeane]

I appreciate all of the opinions and advice. In the end it's part challenge and part fiscal, I would really rather not drop $800+ on a new machine right now. Spending a hundred or so on capacitors and a new soldering station...not so bad.

I'd feel better about buying a brand new box if I was confident that I could clone her existing drive to the new machine. I'm guessing even now most modern equipment has Win7 drivers, so that's a cautious 'maybe'. (We really, really do not want to go Win10.)

[edavid]

I appreciate all of the opinions and advice. In the end it's part challenge and part fiscal, I would really rather not drop $800+ on a new machine right now. Spending a hundred or so on capacitors and a new soldering station...not so bad.

I'd feel better about buying a brand new box if I was confident that I could clone her existing drive to the new machine. I'm guessing even now most modern equipment has Win7 drivers, so that's a cautious 'maybe'. (We really, really do not want to go Win10.)

Why not buy an Optiplex 745 and a Q6600 for < $50 

[Rasz]

I appreciate all of the opinions and advice. In the end it's part challenge and part fiscal, I would really rather not drop $800+ on a new machine right now. Spending a hundred or so on capacitors and a new soldering station...not so bad.

I'd feel better about buying a brand new box if I was confident that I could clone her existing drive to the new machine. I'm guessing even now most modern equipment has Win7 drivers, so that's a cautious 'maybe'. (We really, really do not want to go Win10.)

Why not buy an Optiplex 745 and a Q6600 for < $50 

because he would really rather not drop $800+ on a new machine!

[jimdeane]

Why not buy an Optiplex 745 and a Q6600 for < $50 

With a used machine I make the assumption that it has been taken care of and doesn't have other impending fatal flaws. If I'm replacing this machine, I will go straight to buying new because then I do not have to deal with someone else's problem.

If it were one of my play-around machines, I'd probably do just what  you suggest, or something similar. This one is for my wife's business, so I'm not going to go for the middle options. Either I fix this one right or she'll buy a new one.

[Ian.M]

That puts a different slant on it.  If its business critical, the down-time to re-cap it then burn-in test with a live CD and a 'scratch' HDD is probably unacceptable.  You'd do better to get a spare motherboard and PSU from the same make and model of machine (or even a complete spare machine) and run that while you recap and test the original motherboard.   Alternatively, if you have another PC powerful enough to run a clone of the HDD in a VM, that could also buy you the time to do the job right.

Chances are the PSU may also be developing bad caps.  Suspect small electrolytics on the primary side and all secondary side ones that are immediately after the rectifier diodes.  Failure modes can include grossly excessive ripple on the low voltage rails which is likely to corrupt data, or catastrophic loss of regulation which would destroy at least one and possibly more system components.

Windows 7 support ends 2020, so if you really want to avoid Windows 10 for as long as possible, its worth putting in the time and money to get the spares you need before they become totally unobtainable.

[AlxDroidDev]

Chances are the PSU may also be developing bad caps

Possible, but not a problem directly related to the bad caps on the mobo.  Besides, even if it has, chances are the PSU uses a single sided board, which makes changing components a breeze (I've done it a lot).

My 2 cents: I'd try and fix the board. If it's done carefully, the OP has high chances of success. Besides, fixing the board is "environmentally correct", FWIW.

[Ian.M]

I was just pointing out that downtime on a business PC running critical applications you don't have a hot spare for is far more costly than on a personal/hobby PC.

I agree its worth a shot at fixing the board and that early stage bad caps in the PSU wouldn't contribute to the caps on the board failing..  However it would be a great disappointment if a failing PSU took the board out in a few months time so the PSU should be checked as well. 

[Johnny10]

If this is a critical component in your wife's business.
A new machine makes far more sense.

But if it is an exercise in your learning/experimenting can do attitude go for the capacitor change.
My own experience on what I thought would be easy to do repairs with all my latent skills. And unlimited budget 
Has ended in destroying delicate pads and disturbing surrounding components, Hours wait make that days of searching out components, learning the purpose and design of non-working circuits. Ordering new parts.
It can be overwhelming, but my curiosity always wins in the end and I keep at it until I find the solution. 60 hours later!

The amount of experience and knowledge the members have on this site...
It is worth taking their advice.

[rx8pilot]

I do a lot of repairs that are financially unjustifiable. They can be fun and land me some useful skills that I keep forever. Those skills can become VERY valuable on the day that something MUST be fixed.

I got an old/crusty pick and place machine off eBay about 10 months ago. Totally useless if I was not able to repair a ton of problems. Those repair skills came from all the other repairs and attempted repairs I have done in the past.

[KD0CAC John]

Same here , theres almost never a reason to not try to fix stuff , if for no other reason learning .
I've made a living in ,
Union carpentry
Auto repair
Welding
Gold mining 
Gun smithing
Machining
Plumbing
Electrical res. & com.
Electrical appliance repair
Tower work ham radio & comm.
My main leaning point now is electrical / RF repair
And if it doesn't get fixed , then I fill my empty time with scrapping

[brillopad]

Since it looks like you'll try to desolder the caps.

Forget about wick until you actually have the caps removed from the board. Also, a sucker may not do the trick either, there is plain silly heat sinking capability in those multilayer boards. Drown the leads in extra (fresh) solder usually helps a lot.

Often easier to rip the olds caps off and use the exposed legs to solder on the new cap.

[John_ITIC]

Funny, I just spent a week chasing down my instability issues of my old server motherboard (P4 Abit TH7II-RAID). The system crashed seemingly randomly. MemTestx86 passed fine but I traced down the issue to leaking caps around the RDRAM DIMMs. They looked exactly like your caps. Slight crustiness but no major leak. In my case, I've had that computer for 15 years and have hundreds of applications installed. I also have SCSI cards and a SCSI backup station. Moving to a new computer is a big pain in the neck so I wanted to get this box working reliably as cheaply as possible.

The solution was to replace only the caps that clearly were leaking (around the RDRAM). Other caps around the P4 looked a bit bulged but were fine. I managed to de-solder and solder only with my Hakko 936. A better approach would be to pre-heat the board but I wanted to try the quick and dirty way first and it actually worked. The machine is now up and running reliably again.

I measured the capacitance of the removed caps to about half the rated capacitance.

Sometimes the hardware cost is a minor cost of the system...

[TheSteve]

Funny, I just spent a week chasing down my instability issues of my old server motherboard (P4 Abit TH7II-RAID). The system crashed seemingly randomly. MemTestx86 passed fine but I traced down the issue to leaking caps around the RDRAM DIMMs. They looked exactly like your caps. Slight crustiness but no major leak. In my case, I've had that computer for 15 years and have hundreds of applications installed. I also have SCSI cards and a SCSI backup station. Moving to a new computer is a big pain in the neck so I wanted to get this box working reliably as cheaply as possible.

The solution was to replace only the caps that clearly were leaking (around the RDRAM). Other caps around the P4 looked a bit bulged but were fine. I managed to de-solder and solder only with my Hakko 936. A better approach would be to pre-heat the board but I wanted to try the quick and dirty way first and it actually worked. The machine is now up and running reliably again.

I measured the capacitance of the removed caps to about half the rated capacitance.

Sometimes the hardware cost is a minor cost of the system...

If I found bulged caps I would have swapped them out while I had the board out being the machine is so important to you.

[Cubdriver]

Funny, I just spent a week chasing down my instability issues of my old server motherboard (P4 Abit TH7II-RAID). The system crashed seemingly randomly. MemTestx86 passed fine but I traced down the issue to leaking caps around the RDRAM DIMMs. They looked exactly like your caps. Slight crustiness but no major leak. In my case, I've had that computer for 15 years and have hundreds of applications installed. I also have SCSI cards and a SCSI backup station. Moving to a new computer is a big pain in the neck so I wanted to get this box working reliably as cheaply as possible.

The solution was to replace only the caps that clearly were leaking (around the RDRAM). Other caps around the P4 looked a bit bulged but were fine. I managed to de-solder and solder only with my Hakko 936. A better approach would be to pre-heat the board but I wanted to try the quick and dirty way first and it actually worked. The machine is now up and running reliably again.

I measured the capacitance of the removed caps to about half the rated capacitance.

Sometimes the hardware cost is a minor cost of the system...

If I found bulged caps I would have swapped them out while I had the board out being the machine is so important to you.

Agreed - the bulging ones are on borrowed time - I too would change them before they crap out completely.

If nothing else, order spares so you have them on hand when the time comes...

-Pat

[Nerull]

Why not buy an Optiplex 745 and a Q6600 for < $50 

With a used machine I make the assumption that it has been taken care of and doesn't have other impending fatal flaws. If I'm replacing this machine, I will go straight to buying new because then I do not have to deal with someone else's problem.

If it were one of my play-around machines, I'd probably do just what  you suggest, or something similar. This one is for my wife's business, so I'm not going to go for the middle options. Either I fix this one right or she'll buy a new one.

Read what you just wrote, and then think long and hard about the potential damage you're about to do to this motherboard and still use it it still works afterward. The worst care anyone could possibly take of their equipment, could not compare to what you're about to put the board through. That doesn't mean it won't work, but if you think this procedure is risk free you're nuts.

You're spending $100+ to save $10.

[nctnico]

Those should be KZG series which had problems. Pretty safe to replace just 3 of them. 15W firestick very likely will be too weak but you can try, most likely will need to wait until it heats up after every joint.

15W isn't going to cut it. You'll need 80W + hot air at least. The only way to get these capacitors from the motherboard is pre-heating with hot air and then quickly (before the board cools down) remove the solder with solder-wick once the capacitor has been removed.
I have a similar Dell system which needed the capacitors replaced twice over the years. I guess the on-board PSU puts too much ripple current through the capacitors.

[wblock]

Agreed - the bulging ones are on borrowed time - I too would change them before they crap out completely.

Bulging caps have already failed.  They might show full capacitance, but the ESR increases and they aren't removing the ripple they are supposed to.  The other caps in parallel have to deal with that increased ripple, and they are likely near failure too.  Or already failed, they don't always fail visibly.

[rx8pilot]

Those should be KZG series which had problems. Pretty safe to replace just 3 of them. 15W firestick very likely will be too weak but you can try, most likely will need to wait until it heats up after every joint.

15W isn't going to cut it. You'll need 80W + hot air at least. The only way to get these capacitors from the motherboard is pre-heating with hot air and then quickly (before the board cools down) remove the solder with solder-wick once the capacitor has been removed.
I have a similar Dell system which needed the capacitors replaced twice over the years. I guess the on-board PSU puts too much ripple current through the capacitors.

+1
You can't fake it IMHO.

[John_ITIC]

Agreed - the bulging ones are on borrowed time - I too would change them before they crap out completely.

Bulging caps have already failed.  They might show full capacitance, but the ESR increases and they aren't removing the ripple they are supposed to.  The other caps in parallel have to deal with that increased ripple, and they are likely near failure too.  Or already failed, they don't always fail visibly.

Note that many capacitors have a slightly non-flat upper surface, even as new. I would have replaced all the caps but I didn't have the correct ones in stock. After replacing the bad ones, my board works fine and the voltages are good. If the board acts up in a few years again, then I'll deal with that then. Way too many other fish to fry at the moment.

[nctnico]

Values which are near enough will also work. The Dell machine I mentioned earlier was my server and it crapped out just weeks before it was scheduled to be replaced so I had to make do with what I had in stock.

[jimdeane]

I have a couple of other boards to practice on now, and will have a hot air station and a Weller or Hakko temp controlled soldering station by the time I start. In the meantime she is on my good laptop, which is my motivation.

I'm wondering about capacitor selection. I have cataloged the caps on the motherboard, and will be replacing all of the KZG caps. I've been looking at various manufacturers and series, and I have a question.

I am reasonably sure that having a higher impedance would be unacceptable, but can the values go too low too? I see the KZG 820 is listed at 36 milliohm and 1140 mA rated ripple current. The Nichicon E-HN 820 is rated at 21 milliohm and 1300 mA.  The E-HM is a bit closer to the original KZG rating at 30 milliohms and 1140 mA.

Should I prefer the E-HM over the E-HN due to the closer specs?

[Srbel]

If you go to low, you may end up with similar problem: https://www.eevblog.com/forum/repair/atx-smps-%28tl494%29-output-oscillating/msg800272/#msg800272

:/

[dfmischler]

Should I prefer the E-HM over the E-HN due to the closer specs?

It might not make a difference.  As an anecdotal data point, I replaced the United Chemicon KZG 820uF caps with Nichicon HM 820uF caps on a half dozen boards and have had no further problems with them.

[tjg79]

Check out the Bad Caps Forum:

http://www.badcaps.net/forum/

They sell caps also. They may have a kit for your board.

I don't listen to the naysayers. If you have a bad cap problem, it can be fixed. If you've never done it before, then you get a chance to learn a new skill. You'll get a lot of good help on the bad caps forum.

You can also price caps at Mouser Electronics and Digi-Key Electronics. I find that Mouser usually has the better prices.

Do you have a good soldering iron? I use a Hakko FX-888D. You can get one for about $100.00. Get a $5.00 solder sucker and some good quality solder wick. Stay away from the Chinese crap. For solder, I recommend the Kester 44 Rosin Core .031". You don't want lead-free solder. You'll need a flux pen as well. There are many videos on YouTube that demonstrate good soldering techniques. Everyone into vintage electronics, old computers, or likes to fix electronics should have these tools. They pay for themselves after a few projects.

I also recommend an ESR meter. I like and have a Peak Electronic Design Atlas ESR+ ESR70. It's a very handy tool to identify bad caps in circuit. Not all bad caps have the usually bad cap indications of bulging, swelling and leaking. Some look good until you test them with an ESR meter.

Regards

PS

I also recommend some 99.9% IPA and a camel hair brush. You can price all these items out on Amazon.com.

You want to be very careful and not pull a cap that hasn't been adequately desoldered or had all the solder melted. You can damage the PCB traces and through holes if you get in a rush. Take your time and let the caps fall out.

You don't need hot air to replace electrolytic caps on a motherboard.