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PostPosted: Sun Jun 11, 2017 9:21 pm 
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Pilgrim
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Have searched for many hours for the names and pinouts of the North Bridge and South Bridge chips for the Presario S000 motherboard. Their identity is hidden under heatsinks. The processor is an Athlon XP 2400+. The image of the motherboard attached is of a `generic' [micro]ATX but happens to illustrate a layout identical with the Presario motherboard. The only useful looking number on the motherboard is N1996 which I have added to the motherboard image. Cannot obtain bios information as the PC will not power up (No! It is not the power supply).

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PostPosted: Mon Jun 12, 2017 5:41 am 
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Have moved your post to a more appropriate topic section.

Circuit diagrams and most chip pinouts are proprietary info of the manufacturer of the motherboard. But the chipset itself would have a model number and brand, usually there is a PDF specs file at the provider's site. The chipset may be a 'stock' version, or has been custom made to the specs of the motherboard provider.
Ensure all power sockets on the motherboard are mated to leads from the PSU. There is a 4-pin socket near the 20-pin main power socket. That should have a lead set from the PSU connected. The user manual will detail if that is for an extra mains power source (+3.3 volt) or the AT12 volt so the CPU has its proper power supply.
Are the CPU and memory compatible to the board version? Is the BIOS battery known good? If dead, the system real-time clock will not function, and the system bus clocks may not become active.

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PostPosted: Mon Jun 12, 2017 12:05 pm 
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N1996 is a marking for MSI/Microstar motherboards. There should be another marking somewhere something like MS-6390.

I can only think of two boards from MSI that have that distinctive orange heatsink, which I have a manual for both in my offline collection.

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PostPosted: Mon Jun 12, 2017 7:21 pm 
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Thanks to Karlweldt and Tony B for your responses - this is my second attempt to reply. The first was saved as a draft but now I cannot find it on this forum.
Kalweldt: The PC was working OK a week ago except the momentary ON/OFF switch began to require several presses to turn on the PC and now will not respond at all. The PSU was tested independently `on-load' and was OK in every respect. The 3V battery measured OK and worked in another motherboard. I thought if I had the pinouts of the chipsets, I could measure continuity from the ON/OFF switch and the PS_ON pin at the ATX Power connector back to the chipset. If continuity tests OK, I am in real trouble.
Toby B: Thanks for the tip on MSI boards. It now appears that the N1996 marking indicates conformity with certain supplier regulations and could appear on any motherboard. I suspect the marking is only relevant in Australia. However the distinctive orange heatsink may be a worthwhile clue. Is it possible to look at your two manuals to confirm or otherwise that the processor is an Athlon XP 2400+?


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PostPosted: Tue Jun 13, 2017 4:56 am 
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According to the Compaq User's Guide that came with the PC, the PC was a S0000 Presario. However, another number was discovered on the PC metalwork - S5010AN. Searching on this number lead to an AscendTech web page which describes the mother board (with an image) as an MSI/AWARD and lists the North Bridge and South Bridge chips as being KM266 and 8235. So far, no data sheets or list of pinouts for these chips has been found.


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PostPosted: Tue Jun 13, 2017 8:37 am 
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One critical step of a motherboard coming to life is the PG or 'power good' signal from the PSU being at almost exactly +5 volts. This occurs after the static load of the system stabilizes, and this signal then cues the system clocks to function. If lower than +4.7 volts, possibly no life signs. This could be due to faulted circuit chips or capacitors causing an excessive load on that PG signal.
The front panel header has variable resistance on most pins except the return or grounding pins. Difficult to measure unless you have a good digital meter. For the power and reset front switches, they should show an open circuit when not pressed, and at almost zero resistance when pressed.
For situations like this, a POST diagnostics card is a great tool. It displays a two character code for each step of the power on and boot process. If any character set hangs, that is a clue as to where to start checking. Some can be had for less than $40.00 USD, other 'pro' models go well over $150.00 USD.
Measure all main voltage sources at the main ATX power plug. Any black lead is common to all. Voltages should be within +/-2% to be acceptable, 1% is ideal. The -12 volt source can be off by 3% and still be considered good. One lead (green, near the latch clip) should show about +5 volts, which is the "PS on" control. This is only when the PSU is not working, will go near zero when the PSU is working. Another lead (violet, rear of connector) is for a +5 volt stand-by source. It is always present, if mains power feeds the PSU. Intended for the USB and BIOS needs.
Reference: http://pinouts.ru/Power/atxpower_pinout.shtml

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PostPosted: Thu Jun 15, 2017 5:11 pm 
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Thanks for the tips Karlsweldt.
With a `does not power up' situation, it is a little difficult to measure the PSU voltages, although I was able to do that with an external resistor bank. I did not really check the accuracy, just that all voltages were present and `roughly' correct. I should do it again and check accuracy.
Regarding the POST board, I wonder if they would have enough time to take a reading in a `brief' power-up, if there is any power up at all. I have had a look around for one, don't seem to be stocked in Australia and Amazon will not ship such a board to Australia (they are probably relying on a small supplier that does not want to know about international mail). Will keep looking.

PS: At last, have just found a pdf describing the motherboard South Bridge chip, including at least, the power button pin (PWRBTN).

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PostPosted: Thu Jun 15, 2017 7:52 pm 
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djd, if you can confirm its the MS-6390, I can get a motherboard manual for it. Also, you should be able to post now without the moderator check..

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PostPosted: Thu Jun 15, 2017 9:59 pm 
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Toby B.
Thanks for the response. There are no markings I can identify on the board, but comparing it with the motherboard illustrated and described for the Compaq S5010AN, it `it talks like the mother board and walks like the motherboard' so I am confident that is the one (the South Bridge chip is described as being VT8235 and in fact is a VT8235). I found a pdf describing that chip and the pin for PWRBNT (Pushbutton), but have not found any pin that would be PS_ON (power supply on). I guess I should be looking for `Power OK' as well. If the motherboard manual lists pin outs which include the two just mentioned, then it would be useful to know what they are.

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PostPosted: Fri Jun 16, 2017 7:22 am 
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http://download.msi.com/archive/mnu_exe/E6390v3.0.zip

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