K9A2VM-FD capacitors ?

[bianchi77]

Guys,

I have K9A2VM-FD , it's completely blank out,
I can see some capacitors 1800uF/6.3V are nearly blown,
Are they the cause or it needs chipset reflowing ?

Any experiences ?
Thanks

[mockingbird]

Re: K9A2VM-FD capacitors ?

Most likely it's the caps.

Pics would be nice, but more importantly, post a list of all the caps thusly:

Voltage, Capacitance, Diameter Width, Diameter Height, Brand, Series

Also, which PSU are you using with it?

[bianchi77]

Re: K9A2VM-FD capacitors ?

I see 9 capacitors 1800uF/6.3V with the top bulging...
Now I can't hear any beeps, only I can see CPU fan is running when power supply is connected...
Looks like it can not do POST at all because of those capacitors...
Some photos :

[bianchi77]

Re: K9A2VM-FD capacitors ?

I'm using ATX PSU 300W....L&C technology

[bianchi77]

Re: K9A2VM-FD capacitors ?

Normally it will beep if I don't put CPU and memory in it....
That's what I have experienced before...

[mockingbird]

Re: K9A2VM-FD capacitors ?

1) That PSU is most likely junk.

2) From the pics, I can see 5 different kinds of capacitors on your MB. I see Sanyo WG (Green ones on the VRM high), Toshin Kyogo on the VRM low, Panasonic (next to the northbridge), and UCC KZG series along with more 11.5mm high Toshin Kyogo caps. There is also a small black cap at the top left of the first photo, I can't identify it.

It all boild down to this - replacement caps along with a good PSU is going to cost you more than $50 Australian dollars. Do you want to put that kind of money into such an old system? If so, let me know, and we can proceed further.

[bianchi77]

Re: K9A2VM-FD capacitors ?

I'll fix it..

[bianchi77]

Re: K9A2VM-FD capacitors ?

I've bought some 1800uF/16V for replacement, waiting for delivery..

[bianchi77]

Re: K9A2VM-FD capacitors ?

I measured the capacitance of 1800uF/6.3V on board,
some readings said 4500uF and more than 20000uF, the meaning is open, isn't it ?

[bianchi77]

Re: K9A2VM-FD capacitors ?

I reckon, it's short, I check with multimeter, it's 1K and 18 ohms....
normally...it's showing low resistance and going to OL, open line...

[Wester547]

Re: K9A2VM-FD capacitors ?

The high capacitance readings on those Toshin Kogyo ATWBs are a surefire sign that the aluminum oxide film on the anode is all but consumed by the highly aqueous electrolyte, which also reduces the capacitor's ability to handle the circuit voltage. Those are definitely at least somewhat shorted and are likely to have high leakage current (they won't hold a voltage for long if they still can).

Ultra low ESR, high ripple current handling wet electrolytic capacitors that employ a high concentration of H2O (or ions) in the electrolyte (to increase conductivity) need extremely efficient and special additives, neutralizers, and oxidizers (such as nitrate compounds, phosphate compounds, cathode depolarizers, picric acids, etc...) to protect the aluminum from a phenomenon known as hydration (or the conversion of aluminum to hydroxide) and to prevent foil corrosion. 2001-2005 Nichicon HMs, 2002-2005 Nichicon HNs, and sometimes even 2003-2005 Nichicon HZs and 1999-2005 Nichicon HDs failed in the same manner (although the latter two series at a much lesser rate). Only a few top tier manufacturers (such as Rubycon and Panasonic), at least in the beginning, managed to find the right mixture of inhibitors to suppress the volatile nature of electrolyte that contained 40%-75%+ water content.

In colloquial terms, all the above will certainly destroy the dielectric inside the caps and cause the production of excessive hydrogen gas at the cathode, which has happened in your case (and the more H2O in the solution, the lower the boiling point, so that alone will increase the pressure inside the capacitor as it heats up). And I'm pretty sure those Sanyo (now known as Suncon) WGs are actually the WF series. They're not as reliable as the WG series but they -might- last in the VRM input if the system is cooled and ventilated well. Most ultra low ESR wet electrolytics were discontinued years ago and have all been replaced by functional polymer capacitors, which have come down considerably in price over the years.

I would also highly recommend ditching that L&C and replacing it with a half-decent unit. If you crack it open you are very likely to find a gutless wasteland of failed junk inside.

[bianchi77]

Re: K9A2VM-FD capacitors ?

Will it make active components broken as well? Such as diode and low voltage regulator? Or they still can survive...I ll change the caps later on

[Wester547]

Re: K9A2VM-FD capacitors ?

Not sure if you're making reference to the PSU or motherboard. It's generally bad practice to power computers with gutless wonders (it's a sure way to destroy your components). If you meant the latter, running the motherboard with the VRM low capacitors in that state (or without any there, if the capacitors are desoldered - if you measured them in circuit, it also may explain the high capacitance readings) is a bad idea. When electrolytic capacitors go open, the immense increase in ESR causes the duty cycle of the MOSFETs to increase until they (and the coils) burn themselves out more or less. When they fail shorted, they can take out the MOSFETs with them as well as the chips they're filtering noise for.

This is especially an issue for buck DC-DC converters such as this one. Buck regulators need some sort of capacitor (in this case, the capacitance inside the output capacitors) on the output in order to work properly and store energy - otherwise, whatever chip that buck regulator is for will get a nice dosage of that "energy" and in massive voltage spikes at that.

[bianchi77]

Re: K9A2VM-FD capacitors ?

I've checked some FET there, look like they're good...but I have no idea with the small regulator buck....or a small chip nearby is a switcher, will they get the effect from the capacitor ? 8 pins SOIC L6741 from ST
http://www.st.com/content/ccc/resour...CD00168745.pdf

[bianchi77]

Re: K9A2VM-FD capacitors ?

Does anyone have the schematic for MS-7501 VER:1.0 ?

[bianchi77]

Re: K9A2VM-FD capacitors ?

PCB photos :

[bianchi77]

Re: K9A2VM-FD capacitors ?

I have replaced all the capacitors....is it ok to test now ? or there's a way safer...
so I will not blow my Power supply again....probably fuse on 12V and 5V rail ?

[bianchi77]

Re: K9A2VM-FD capacitors ?

I've check ( in circuit ) there's no short on FET...

[bianchi77]

Re: K9A2VM-FD capacitors ?

It's working now....beep three times....no memories