Top 10 diagnosis

[agentLX]

recently i encountered some PCs with...

symptoms are...

1. i press the power

2. the fans (cpu, video, psu) do spin

3. the motherboard led lights up

4. the system does not beep even though ita signal beep was enabled

5. no display on the monitor, blank screen



i tried ...

1. resetting the bios

2. disconnecting all the components - cables, ram, video, pci card, cpu
etc. -> power on the PC and still no beeps

3. also tried testing the whole system with a working psu, cpu, video card, ram, from a good computer

but the result was the same.

another question also lingers, "how do we know that the cpu is working with the Mobo"?



________________________
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[saphalline]

"how do we know that the cpu is working with the Mobo"?If you've already tried all those steps and it's still not working, then the simple answer is "the CPU isn't working with the mobo!" You've replaced every questionable part except the mobo. That's gotta be the problem. They do die every now and then. (Or it could possibly be that the CPU's and mobo's are incompatible - post the specs and I can tell you if that's the problem - otherwise it looks like dead mobo's.)

Check to see if the mobo and/or system is still under warranty. If not, you'll have to decide if it's worth trying to track down replacement mobo's. If the systems are really old, it might not be worth it...

[jep]

Also try to test all those parts in another PC. A working one. aight!

[agentLX]

its an amd duron, actually it was functioning well now and then, so theres no compatibility issue.

suddenly it does not function any longer, and its out of warranty (...talk about duron).

is it possible that the mobo is dead,
1. when its onboard led is still lighting
2. the cpu & chassis fans do spin, which means that the board do get current

[Sylvander]

Does the POST appear to be running?
Any signs of flashing LED's?

If it IS beginning, then one or more tests are failing without any beeps being generated [assuming the internal speaker is working], and then unable to complete or is teminating.
Here's a generic PhoenixBIOS:

The following is a list of the checkpoint codes written at the start of each test and
the beep codes issued for terminal errors. Unless otherwise noted, these codes
are valid for PhoenixBIOS 4.0 Release 6.x.

Code_Beeps_POST Routine Description
02h Verify Real Mode
03h Disable Non-Maskable Interrupt (NMI)
04h Get CPU type
06h Initialize system hardware
07h Disable shadow and execute code from the ROM.
08h Initialize chipset with initial POST values
09h Set IN POST flag
0Ah Initialize CPU registers
0Bh Enable CPU cache
0Ch Initialize caches to initial POST values
0Eh Initialize I/O component
0Fh Initialize the local bus IDE
10h Initialize Power Management
11h Load alternate registers with initial POST values
12h Restore CPU control word during warm boot
13h Initialize PCI Bus Mastering devices
14h Initialize keyboard controller
16h 1-2-2-3 BIOS ROM checksum
17h Initialize cache before memory Auto size
18h 8254 timer initialization
1Ah 8237 DMA controller initialization
1Ch Reset Programmable Interrupt Controller
20h 1-3-1-1 Test DRAM refresh
22h 1-3-1-3 Test 8742 Keyboard Controller
24h Set ES segment register to 4 GB
28h Auto size DRAM
29h Initialize POST Memory Manager
2Ah Clear 512 kB base RAM
2Ch 1-3-4-1 RAM failure on address line xxxx*
2Eh 1-3-4-3 RAM failure on data bits xxxx* of low byte of
memory bus
2Fh Enable cache before system BIOS shadow
32h Test CPU bus-clock frequency
33h Initialize Phoenix Dispatch Manager
36h Warm start shut down
38h Shadow system BIOS ROM
3Ah Auto size cache
3Ch Advanced configuration of chipset registers
3Dh Load alternate registers with CMOS values
41h Initialize extended memory for RomPilot
42h Initialize interrupt vectors
45h POST device initialization
46h 2-1-2-3 Check ROM copyright notice
47h Initialize I20 support
48h Check video configuration against CMOS
49h Initialize PCI bus and devices
4Ah Initialize all video adapters in system
4Bh QuietBoot start (optional)
4Ch Shadow video BIOS ROM
-----------------------------------------
Your POST doesn't get to here.
4Eh Display BIOS copyright notice
-----------------------------------------
4Fh Initialize MultiBoot
50h Display CPU type and speed
51h Initialize EISA board
52h Test keyboard
54h Set key click if enabled
55h Enable USB devices
58h 2-2-3-1 Test for unexpected interrupts
59h Initialize POST display service
5Ah Display prompt "Press F2 to enter SETUP"
5Bh Disable CPU cache
5Ch Test RAM between 512 and 640 kB
60h Test extended memory
62h Test extended memory address lines
64h Jump to UserPatch1
66h Configure advanced cache registers
67h Initialize Multi Processor APIC
68h Enable external and CPU caches
69h Setup System Management Mode (SMM) area
6Ah Display external L2 cache size
6Bh Load custom defaults (optional)
6Ch Display shadow-area message
6Eh Display possible high address for UMB recovery
70h Display error messages
72h Check for configuration errors
76h Check for keyboard errors
7Ch Set up hardware interrupt vectors
7Dh Initialize Intelligent System Monitoring
7Eh Initialize coprocessor if present
80h Disable onboard Super I/O ports and IRQs
81h Late POST device initialization
82h Detect and install external RS232 ports
83h Configure non-MCD IDE controllers
84h Detect and install external parallel ports
85h Initialize PC-compatible PnP ISA devices
86h Re-initialize onboard I/O ports.
87h Configure Motherboard Configurable Devices
(optional)
88h Initialize BIOS Data Area
89h Enable Non-Maskable Interrupts (NMIs)
8Ah Initialize Extended BIOS Data Area
8Bh Test and initialize PS/2 mouse
8Ch Initialize floppy controller
8Fh Determine number of ATA drives (optional)
90h Initialize hard-disk controllers
91h Initialize local-bus hard-disk controllers
92h Jump to UserPatch2
93h Build MPTABLE for multi-processor boards
95h Install CD ROM for boot
96h Clear huge ES segment register
97h Fix up Multi Processor table
98h 1-2 Search for option ROMs. One long, two short
beeps on checksum failure
99h Check for SMART Drive (optional)
9Ah Shadow option ROMs
9Ch Set up Power Management
9Dh Initialize security engine (optional)
9Eh Enable hardware interrupts
9Fh Determine number of ATA and SCSI drives
A0h Set time of day
A2h Check key lock
A4h Initialize typematic rate
A8h Erase F2 prompt
AAh Scan for F2 key stroke
ACh Enter SETUP
AEh Clear Boot flag
B0h Check for errors
B1h Inform RomPilot about the end of POST.
B2h POST done - prepare to boot operating system
B4h 1 One short beep before boot

[agentLX]

no theres no POST test
the monitor is completely blank, monitor led - orange lit
but my video card and monitor are in good condtion.

[Paleo Pete]

OK, it's not clear so far just how thoroughly the hardware has been tested. I would suggest a couple of things, and do your testing one item at a time.

Check it for Bad Capacitors (http://www.pcguide.com/vb/showthread.php?t=25482). If you find even one bad one, it's time for a new motherboard. The only way to repair it is to solder in new capacitors of the exact same values and physical size, and I think I've known 3 people my entire life, including myself, who could solder well enough to do it. Usually you have no more than 1/8" clearance for mistakes and dribbles.

Test, in THIS computer:

Known good power supply
Known good video card
Known good RAM
Existing RAM, one chip at a time
Known good CPU

In that order. Be careful with the CPU and make sure the thermal compound is in good condition. When I remove and swap one I ALWAYS use new thermal compound, even for 5 minutes' testing purposes.

I'm guessing here, but I'm suspicious of power supply and capacitors. If none of that isolates a bad part, take the motherboard out of the case, set it up on a non-conductive surface (cardboard on a tabletop will work fine) and try it with Motherboard, CPU/heatsink/fan, RAM, video and keyboard. Swap video card and RAM first, if still no picture, then CPU. If you do get results on a tabletop as a bare bones setup, it's a ground problem so check for anything that could be getting shorted against the chassis, especially the standoffs holding the motherboard. I've had to use all plastic ones before...

[agentLX]

When I test a computer, i test its component one at a time by getting another working computer with the same specs.

How do i test a power supply using a tester? what reading in each pin should i get?

[Variable]

Sounds like a bad motherboard to me.