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Badcaps Biostar NF4ST-A9 capacitor repair

On this page we are going to show you an example of bad capacitors on a computer motherboard. We will discuss the motherboard specification, the symptoms of this problematic board and the final repair outcome of this motherboard.
BioStar Motherboard NF4ST A9
We were recently given a computer which would itermitently freeze and lockup especially on online gaming. Most of the time when the computer froze the speaker would also give a constant static noise..

On opening the computer casing we noted that the motherboard was a Biostar NF4ST-A9 with an AMD Athlon X2 3800+ 2Ghz Dual Core socket 939 CPU. The main memory ram installed was 4 sticks of DDR1 memory totalling 2GB. The graphics dispaly was via the PCIe  HD4350 graphics card with the TV monitor plugged into the HDMI port. Storage was supplied by the Western Digital 500GB SATA hard disk drive.

Straight away we noticed when looking at the main motherboard that one of the electrolytic capacitors was bulging and had leaked.
This capacitor was located near to the CPU heatsink.

Actual component testing on todays modern circuit boards can be quite difficult without test instruments. The use of specialist test meters and equipment is the only way to satisfactorily test components.
Not everyone will have access to the specialist test equipment. We can however sometimes assume failure of some components by visually looking at these components.

Visual checking of a capacitor to determine failure is one example where an electrolytic capacitor will look different to a good electrolytic capacitor on a circuit board.

For a basic understanding of what a capacitor is and what it does you can either google for more information or you can visit our web page  

Below the image on the left shows what a good capacitor should look like. On the right image we show an example of a bad capacitor. You will notice that the bad capacitor casing on top is bloated where as the good capacitor on the top is completely flat..

Good Capacitor     Bad Capacitor

Image on the left shows a Good Capacitor ---- Image on the right shows a Bad Capacitor

You may also notice that a bad capacitor like ours had leaked from the top or bottom with its electrolytic content. Capacitors can also go bad and show no visible signs. The only way to test a capacitor which shows no visible signs of failure is to measure the capacitors ESR and capacitance value using an ESR meter. You can read our review on a great budget meter called an ESR Micro which can be used for the correct method for testing capacitors on

On our motherboard we had five 3300uf 6.3V capacitors located near to the CPU and three 1500uf 16V capacitors elsewhere on the board  which we suspected as bad capacitors.

bad caps near cpu

As you can see on the image above the four capacitors which are next to the CPU heat sink are showing no visible signs of breakdown but the fifth capacitor missing from our image was bulging with some signs of electrolytic leakage.

All these capacitors were manufactured by Nichicon and from their KZG series.
We no from experience that this series of capacitor can oftern fail showing no signs of any defects. Indeed it is recommended that all capacitors within the motherboard from the KZG series be replaced regardless of the current condition.
Nichicon no longer manufacturer the KZG series of capacitor but do manufacturer other series which would be a good replacement and better quality for our motherboard.

The replacement capacitors we chose for our motherboard were the Nichicon from their HZ series. We confirmed from the manufacturers data sheet that this replacement would be of better specification for replacing our bad capacitors. It is very important that the replacement capacitors specification is of a similar or higher quality as not all series of capacitors are suitable for the design of their functionality.

Nichicon 1500uf 16v Series HZ          Nichicon 3300uf 6.3v Series HZ     

It is advisable prior to removing the capacitors to make a sketch or take photographs of where the capacitors are located on the motherboard. The last thing you would want is to forget which capacitor came from which location on the motherboard. You certainly don't want to be putting in the wrong capacitors in the wrong location of the motherboard. You must also take your time and double check each task when carrying thiese procedures.

Removing capacitors on modern motherboards can be quite tricky. Most modern motherboards are made of multiple layers interconnecting each layer. Care must taken that the layers not visible on a motherboard are not damaged when soldering or de-soldering. When removing these components the soldering iron must be clean and hot enough to melt the solder but not to hot that it will cause heat damage to the circuit board tracks which may be visible or located within the un-visible layers of the board. A good tip is to heat the lead of the capacitor and wiggle and pull on one side then heat the other lead and do the same to that. Eventually the capacitor will come out. The other problem you may encounter is once the capacitor has been removed the component hole is completely blocked with solder. Our tip to unblock these holes is to apply some more solder on the blocked hole and then use a solder sucker tool to suck the solder out of the hole. If you find that the solder sucker is not totally unblocking the component hole then pushing a stainless steel needle into the hole while holding the hot soldering iron on to the blocked hole sometimes helps. The hot solder should not stick to the stainless steel needle and therefore this tip should work.
Caps removed

Once the capacitors have been removed you should inspect the motherboard with a magnifying glass to ensure that no solder that should have been removed is shorting the board. If all looks well then you are ready for the next procedure.

If you look at the image above, of the motherboard with the removed capacitors you will notice where the capacitors came out there is a symbol of a circle with one side coloured white. This white coloured area shows us the polarity of the capacitor to be negative on this white coloured side. The polarity of the capacitor is very important for the correct function of the capacitor.

On our motherboard we chose our replacement of capacitors manufactured Nichicon. We wanted to ensure our replacement capacitors were sourced from reputable manufactures. We chose the same value capacitance and voltage for our replacement capacitors. You can use higher voltage capacitors but you should ensure that the capacitor leads are not to thick to put back into the motherboard component hole.

Once the new capacitors have been put into the motherboard always double check before soldering that the correct values have been used. It is quite easy to confuse and mistakenly use a 100uf capacitor instead of the correct value 1000uf. Also check that you have inserted correctly the polarity of the capacitor.

When soldering the new capacitors make sure that your soldering iron tip is clean and tinned. Then solder your new replacement capacitors ensuring that you obtain a good clean shiny soldered joint.

new caps on mb

Above you will see an image of the motherboard with the new replaced capacitors.

On completion of the soldering task you may want to clean the excess flux deposits left behind by the soldering. We normally use a cotton bud dipped into alcohol which works fine for us. Now is also a good time to re-check the new capacitors to ensure that the correct values have been used and that the motherboard is clean and ready for re-installation.

On re-installation of the motherboard into the PC tower case we ensured that all the add on cards and memory went back into the same slots as originally found prior to stripping out the motherboard. If you do end up using a different slot for your add on card or memory you may find that the PC will not re-boot until you have cleared the CMOS and loaded the default factory settings. Your motherboard manual should help to locate the correct jumper on the motherboard to clear CMOS if you find you have a blank screen.

For us the motherboard switched on straight away and booted straight in to the Windows 7 operating system with out any problems. We used Everest to stress test our repaired motherboard for two hours without encountering any problems.

On completion we decided to test the faulty removed capacitors using the ESR Micro V4 for measuring the capacitance and ESR readings.

A good 3300uf capacitor should give us a measured capacitance reading of the same value subject to the manufactures tolerance of about 10% either side of the tolerance value. We would also expect the ESR measured reading to be approximately 0.02 ohms. Testing the removed bulging capacitors gave us typical measured readings of 4510uf capacitance and an ESR measurement of 0 ohms for the 3300uf capacitor. This clearly showed that these capacitors were faulty and if left in their current state they could have caused more severe problems to other components on the motherboard.

The ESR reading is very important and  the typical ESR measurement of 0 ohms showed that these capacitors were generally shorting.
If a capacitor is shorted then the DC resistace will be equal to zero. The majority of ESR meters detecting this failure will indicate the measured reading as 0 (zero) ohms.
In our final conclusion we can say that replacing the bad capacitors on this motherboard completely resolved our previous problematic issues. Our motherboard seems also quicker in load times and faster over all.

The whole cost of the five 3300uf 6.3V and two 1500uf 16V capacitors was 10.73 GBP including shipping from a reputable supplier within the USA. The whole task of replacing the capacitors took approximately thirty minutes.

We hope our readers have enjoyed this article on replacement of faulty bad capacitors on computer motherboards and will come back to for our views on more technological products.

Watch the video below and see bad capacitors on other motherboards
The second video shows capacitor being replaced on a imac G5     

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