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Old 05-12-2018, 07:57 PM   #1
Stefan Payne
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Default ASUS A7M266 Kills T-Bred B??

I got a used A7M266 (1.04)

And tried putting in a T-Bred B from wich I was certain it still worked - and it died.


With some Measurements:
the V-Out of the CPU VRM was around 0,3V - and getting really really hot...
With a TBird it is around 1,85V and works more or less...

I tried setting the Voltage manually, didn't change anything (well, it was ~1,65V without the CPU. And also with the TBird)...

Another Thing: one of the 4V/820F Caps (those Yellow Fujitsu or so).

What can I do??
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Old 05-18-2018, 11:21 PM   #2
Stefan Payne
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Default Re: ASUS A7M266 Kills T-Bred B??

I've desoldered those Yellowish Fujitsu Caps (4V/820F) because one looked odd.
And they measure between 1100 and 1572F wich seems a bit odd/defective...
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Old 05-19-2018, 02:06 AM   #3
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Default Re: ASUS A7M266 Kills T-Bred B??

Leaky I suppose, if it's measuring high.
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Old 05-25-2018, 10:21 PM   #4
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Default Re: ASUS A7M266 Kills T-Bred B??

Interesting problem.

I would say replace those yellow Fujitsu caps if they are measuring high capacitance, as they might be getting leaky, as Agent24 suggested. Furthermore, when I looked for images of the board online, I found this:
https://www.anandtech.com/show/845/3
If you enlarge the picture on that site, you will see that the Fujitsu caps on that board are bulged. Makes me curious if that's due to a board design error or if Fujitsu caps like that are failure-prone (or at least the early ones).

As for replacements, you could probably use regular 6.3V electrolytics if that's all you have (Rubycon ZL or Chemicon KZE minimum). Or go with polymers again.
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Old 05-26-2018, 09:25 AM   #5
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Default Re: ASUS A7M266 Kills T-Bred B??

The early Fujitsu polymers are failure prone. Back in the day, it was initially conjectured that it was because of insufficient rubber seals allowing moisture ingress which resulted in a steady increase in ESR (and eventually, said moisture evaporating to steam). Due to those high capacitance readings, though, its probably the result of residue from acidic iron compounds that are used as the oxidant for the PEDOT polymerization process. The iron particles remain in the capacitor even after polymerization, which causes leakage current to increase over time (and high leakage current usually means defects in the aluminum oxide).

The specs on those polymers should be about 5040 mA for the allowable ripple current at 105C and 12 milliohms for ESR. So, if its worthwhile to you, polymers are probably the best bet for replacements.
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Old Yesterday, 12:37 AM   #6
Stefan Payne
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Default Re: ASUS A7M266 Kills T-Bred B??

I tried and now it has the same issue (but with 0,8V) with the TBird Chip...

I used two (later 3) Panasonic FR with 2200F/10V and 470F/25V Panasonic FM.
Also used 470F/16V Polymers first.

w/o CPU its 1,7V...

Last edited by Stefan Payne; Yesterday at 12:38 AM..
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Old Yesterday, 05:40 AM   #7
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Default Re: ASUS A7M266 Kills T-Bred B??

So maybe you have bad VID signal to the VRM controller. I get the impression you are trying to use an unsupported CPU as well?
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Old Yesterday, 07:09 AM   #8
Stefan Payne
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Default Re: ASUS A7M266 Kills T-Bred B??

I can override the VID (and I did), that isn' the Problem.
W/o something in the Socket everything seems fine, though I don't have a Scope.

However when I insert a CPU (even the TBird), the voltage of the VRM is way lower than it should ant it cooks itself.
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Old Yesterday, 04:19 PM   #9
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Default Re: ASUS A7M266 Kills T-Bred B??

What cooks itself? The CPU or the VRM?

Maybe you've managed to short both CPUs now or the VRM controller is instead\also damaged.

Did you try the CPU in another board?
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Old Yesterday, 04:22 PM   #10
Stefan Payne
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Default Re: ASUS A7M266 Kills T-Bred B??

Quote:
Originally Posted by Agent24 View Post
What cooks itself? The CPU or the VRM?
VRM of course.


Quote:
Originally Posted by Agent24 View Post
Did you try the CPU in another board?
Only the defective TBred-B.
And it didn't work but voltage seemed fine, if I recall (on an MSI NF2-S Thingy)
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