Return of "What is JS214A?"

[Watson A.Name - \"Watt Su]

"Franc Zabkar" <fzabkar@optussnet.com.au> wrote in message
news:4a2lh0let9lqr3dmmo3vintapn8rncmam9@4ax.com...

On Wed, 11 Aug 2004 11:32:46 GMT, "alpha_uma" <no_one@nonesuch.com
put finger to keyboard and composed:
[snip]

FWIW, here are my notes for an M571/M571lmr socket 7 motherboard which
uses a Vcore circuit similar to yours:
http://members.optusnet.com.au/~fzabkar/LMRvcore.txt
http://members.optusnet.com.au/~fzabkar/pwrnotes.txt
http://members.optusnet.com.au/~fzabkar/v32corev.txt
http://members.optusnet.com.au/~fzabkar/voltcalc.txt
http://members.optusnet.com.au/~fzabkar/voltcore.txt

The LMR board uses BIOS to control the Vcore (probably similar to
yours), the other uses jumpers.

This is all fine and well. But meddling with the Vcore means you're
presumably also going to meddle with the CPU or clock speed. And that's
a whole 'nother story.

- Franc Zabkar
--

 

[alpha_uma]

"Franc Zabkar" <fzabkar@optussnet.com.au> wrote in message
news:so3mh010m0e8u49k3s48fqfbemqsmd3d51@4ax.com...

On Wed, 11 Aug 2004 11:32:46 GMT, "alpha_uma" <no_one@nonesuch.com
put finger to keyboard and composed:

Here is a link to a picture of my motherboard:
http://members.shaw.ca/ra11dec50/my_mosfets.jpg

On 3/8/04 you wrote that "the three electrolytic caps around these six
MOSFETs are already confirmed bad out-of-circuit, and I replaced them
with good ones." However, in your picture the three caps still look
swollen, or is the poor focus playing tricks with my eyes?


- Franc Zabkar

Franc, you have good eyes. Those three 3300uF caps are indeed the swollen
ones. The picture was taken before I replaced them with good ones. In fact,
I also replaced the following caps even though they were not swollen:

(a) The group of four caps at the top of the picture. These were also 3300uF
caps, but they were later found to be "good" (meaning that they passed the
CRUDE testing routine with my DMM).

(b) A 1000uF cap near the ATX power socket. That is the one right below the
ATX power socket in the picture. It was found to be "good" later.

But these cap replacements did not solve the problem.

I thought about replacing the four green 1500uF caps (two of them next to
the memory socket on the right side of the picture and the other two right
above the AGP socket). That was when I started to question my basic
assumption that it was only a "bad caps" problem, and started suspecting the
MOSFETs and began posting on this newgroup and the "repair" newsgroup
seeking advice on MOSFET testing.

I think I will take a few days to read up on typical power regulation
techniques on motherboards (including those information you and others have
posted) to learn something. Meantime, I'm feeling adventurous, so I may
decide to go ahead and order half-a-dozen or so replacement 2SK3296 MOSFETs
(plus other stuffs to make up a minimum order) from DigiKey and see if I
have any luck.

Al-U

 

[Franc Zabkar]

On Thu, 12 Aug 2004 03:33:43 -0700, "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> put finger to keyboard and
composed:

"Franc Zabkar" <fzabkar@optussnet.com.au> wrote in message
news:4a2lh0let9lqr3dmmo3vintapn8rncmam9@4ax.com...
On Wed, 11 Aug 2004 11:32:46 GMT, "alpha_uma" <no_one@nonesuch.com
put finger to keyboard and composed:
[snip]

FWIW, here are my notes for an M571/M571lmr socket 7 motherboard which
uses a Vcore circuit similar to yours:
http://members.optusnet.com.au/~fzabkar/LMRvcore.txt
http://members.optusnet.com.au/~fzabkar/pwrnotes.txt
http://members.optusnet.com.au/~fzabkar/v32corev.txt
http://members.optusnet.com.au/~fzabkar/voltcalc.txt
http://members.optusnet.com.au/~fzabkar/voltcore.txt

The LMR board uses BIOS to control the Vcore (probably similar to
yours), the other uses jumpers.

This is all fine and well. But meddling with the Vcore means you're
presumably also going to meddle with the CPU or clock speed. And that's
a whole 'nother story.

True, but I thought the OP might benefit from an understanding of how
the Vcore regulator works, especially as he/she appears determined to
attempt a component level repair.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.