Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Jay Walling
 
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Default Repair solution: VIA EPIA-V motherboards fail to POST on power up.

Overview: We have roughly 100 of these Via Embedded manufactured boards,
and 60 of them (give or take a few) exhibited a rather odd power up
problem.

Symptoms: after the board is powered off for roughly 10 seconds or more,
*and* +5SB is still applied through the ATX connector, (a very common
condition) the power on button connected to the front panel connector
would power up the board, but there are no POST codes to port 80. No #CS
or #OE occurs to the flash BIOS which would signal a code fetch after
reset. In other words, the board is completely and utterly dead. Removing
power completely from the power supply would allow the board to recover,
*or* a power up, power down and then a quick power up would also recover
the CPU board. Additionally, when the board is dead, pressing the reset
button 10 or 20 times would also recover the CPU.

Using a 'scope, I noticed that the "high" signal levels on the two
14.318MHz Oscillators on U19 pins 10 and 12 were of rather marginal
voltage levels, barely making it above 2 volts. (and even then, only for
about 6ns or so...)

The pullup termination is currently 100 ohms to 3.3VDC. Changing the two
resistors to 75 ohms has improved the signal levels and has fixed the
problem on 3 boards that I've tried so far. I just found the fix today
after struggling for several days. Now to repair the rest... The two
resistors are located right next to U19 (a 14 pin chip marked LVC07 and
very close to the DIMM and J13), and the resistors connect to pins 12 and
10 of the chip. The device is an open collector non-inverting buffer
similar to a 7407. The resistors are right next to the chip pins as well.
Doing a little tracing, I believe that one of the oscillators drives the
southbridge, but I was unable to trace the other. Perhaps the northbridge?

Anyways, get out your magnifying glass! If you don't like the idea of
replacing the parts, you could also solder 300 ohm SMD resistors right on
top of the existing ones for a parallel resistance of 75. Good luck!

[Please remove mybrain to reply by email]

--
Jay Walling
Diagnostic Engineer

Comark Corporation
93 West St.
Medfield, MA 02052
http://www.comarkcorp.com

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Jay Walling
 
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Default

On Tue, 15 Feb 2005 15:26:13 -0500 Jay Walling
wrote in Message id:
:

Overview: We have roughly 100 of these Via Embedded manufactured boards,
and 60 of them (give or take a few) exhibited a rather odd power up
problem.

Symptoms: after the board is powered off for roughly 10 seconds or more,
*and* +5SB is still applied through the ATX connector, (a very common
condition) the power on button connected to the front panel connector
would power up the board, but there are no POST codes to port 80. No #CS
or #OE occurs to the flash BIOS which would signal a code fetch after
reset. In other words, the board is completely and utterly dead. Removing
power completely from the power supply would allow the board to recover,
*or* a power up, power down and then a quick power up would also recover
the CPU board. Additionally, when the board is dead, pressing the reset
button 10 or 20 times would also recover the CPU.

Using a 'scope, I noticed that the "high" signal levels on the two
14.318MHz Oscillators on U19 pins 10 and 12 were of rather marginal
voltage levels, barely making it above 2 volts. (and even then, only for
about 6ns or so...)

The pullup termination is currently 100 ohms to 3.3VDC. Changing the two
resistors to 75 ohms has improved the signal levels and has fixed the
problem on 3 boards that I've tried so far. I just found the fix today
after struggling for several days. Now to repair the rest... The two
resistors are located right next to U19 (a 14 pin chip marked LVC07 and
very close to the DIMM and J13), and the resistors connect to pins 12 and
10 of the chip. The device is an open collector non-inverting buffer
similar to a 7407. The resistors are right next to the chip pins as well.
Doing a little tracing, I believe that one of the oscillators drives the
southbridge, but I was unable to trace the other. Perhaps the northbridge?

Anyways, get out your magnifying glass! If you don't like the idea of
replacing the parts, you could also solder 300 ohm SMD resistors right on
top of the existing ones for a parallel resistance of 75. Good luck!

[Please remove mybrain to reply by email]


Ugh - the problem has resurfaced when the Northbridge is heated up to 40c
or so. The final solution (hopefully)? Install a 2.7K resistor in location
R20. Currently on our boards, the location is not populated. The resistor
is located about 5mm from the onboard speaker. A difficult install as it's
surrounded by the speaker, the PCI connector and a small electrolytic -
but it can be done.

My question now is: Why no response from VIA on their web based forum
http://forums.viaarena.com/messagevi...IA-V+AND+power
FOR A KNOWN DESIGN FAULT?

Do they care so little for their customers? When I need
support for an Intel product I always get a response within 24
hours. Why can't VIA do the same?

[Please remove mybrain to reply by email]
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NSM
 
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Default


"Jay Walling" wrote in message
...

My question now is: Why no response from VIA on their web based forum

http://forums.viaarena.com/messagevi...IA-V+AND+power
FOR A KNOWN DESIGN FAULT?


Welcome to the 21st century. So much for the Jetsons. The only support most
manufacturers will give you now is a stick up your ass.

N


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