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Author Topic: Wierd Voltage On Lpc Pin 1 & 5  (Read 38 times)

RekaN

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Wierd Voltage On Lpc Pin 1 & 5
« on: May 20, 2004, 01:46:00 AM »
Hi have have an fragging xbox. have have solder about 40-50 xbox and all of them  have been sucessful solder, sometimes the second time.. but this one i have been working on for over an week, have been resolder and heating it alot of times.

can't get it to work.
the box is an version 1.1, old powersupply contact with no fan on the pcu.
I have checked the traces according to
(IMG:http://pictures.xbox-scene.com/3/lpc-diag/lpctest.jpg)

all pins have contact.

and yes.. i have tried alot of working chips on the box. non want to work.
and all have the the X2 XX81 bios and some have M7.
+++++++++++++++++++++++
(IMG:http://pictures.xbox-scene.com/3/lpc-diag/lpc.jpg)
When i messure the voltage
I get pin 5 to 0.18 volts.

and the pin 1 (LClk) gets 1.4 volts (while fragging) and 0 Volts (after fragging restarted 2 times and blinking red)

rest is ok. gets 3.3 v on the one that should have 3.3v and got 5 v on pin 6

sorry for my bad english. hope any1 have any ide what i could text next

/rekan

This post has been edited by RekaN: May 20 2004, 08:49 AM
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opjose

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Wierd Voltage On Lpc Pin 1 & 5
« Reply #1 on: May 20, 2004, 04:33:00 AM »
Have you tried tracing the signal from each pin on the LPC port back to it's first "VIA" on the motherboard?
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e8mange

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Wierd Voltage On Lpc Pin 1 & 5
« Reply #2 on: May 20, 2004, 05:56:00 AM »
Have you checked the D0 voltage? It is supposed to be 5V unless you have grounded it. Also check the BIOS TSOP. I have had some Xbox where the TSOP where broken, if the TSOP is busted the nVidia MCPX chip may have taken some damage to. One approach is to measure the resistance over the resistor R7D1 next to the TSOP. It should be about 10 KOhm.

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hippo

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Wierd Voltage On Lpc Pin 1 & 5
« Reply #3 on: May 20, 2004, 06:49:00 AM »
Since Lframe goes low for one clock cycle of the 33mhz bus then goes high for 18 bus cycles then low for one and high for 273 cycles I doubt your multimeter is registering any of that. Lrst is logic high until 3 other signals go low then it goes low for at least 160us. You are wasting your time measuring data lines for dc voltage when for example Lclk changes state every 33mhz bus cycle meaning the 3.3v peak to peak  that is there is reading 1.65.

This post has been edited by hippo: May 20 2004, 01:53 PM
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RekaN

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Wierd Voltage On Lpc Pin 1 & 5
« Reply #4 on: May 20, 2004, 10:26:00 AM »
@opjose.. yes traced all signal from each pin on the LPC port back to it's first "VIA" on the motherboard.. all was ok .. that is the strange thing

@e8mange: got 10 kohm on R7d1, that one was ok. but when i dissconnect d0 from GND and messure it. it got some values while box was fragging two times, but when start button went red the voltage on d0 was down to 0 v
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