1. Case Analysis
Sephiroth Kwon
GRMA

2. OUTLINE
“all dots”
“00”

3. All dots What is the “all dots”?
“All dots” means that there is only power supplied to DEBUG CARD, but no RESET# or CLK signals. All the LEDs will display “dot”. The problems should be:
We call it as “no frequency, no reset”.
When there are a few of main power abnormal which lead to the CLK_PG invalid. Then the chips which need CLK signal can’t work, and they can’t generate reset signal.
The other condition is “there is frequency, but not reset”.
Some parts of the reset circuit are destroyed or running conditions are not all supplied. Because there is a lack of the reset signal, the debug card displays “all dots”.

4. All dots
NOTICE
Sometimes, the DEBUG CARD only reflects the problem on the PCI Bus. The status DEBUG CARD can’t completely indicate the problem on other bus. So, sometimes we need to measure the other bus’s rest signal.
For example, although the DEBUG CARD displays “all dots”, the board can power on. Then you would find the basis voltage and frequency are good. When this happened, you should measure the other bus’s reset signals, CPURST#, and LPCRST # and so on. The other reset signals are all OK, it just is that the PCIRST# is failed. We usually call this “fake all dots“.

5. All dots How to confirm this kind of problem
Visual Inspection to check whether the board or components are damaged. Check whether there is trace broken.
Visual Inspection
Measure the frequency of crystal resonator, and check the voltage of “3VSB”.
Measure “3VSB” and KHz
Put on the CPU & Port 80 card, then power on. “FF” display on the card. Then put on the DEBUG CARD (the big one), “….” display on the card.
Put on debug card

6. All dots Example - M2A-VM “all dots”: Visual Inspection
VCORE, frequency, PWROK
Measure the SOCKET940 signals with oscillograph ：
1.+1.8V_DUAL, VTT_DDR; 2.VDDA_2.5, VCORE; VHT; 4.C_CK_HT_CPU; 5.H_CPU_PWROK
All of above signals are OK. But no PCIRST# is low means this is a “there is frequency, but not reset” case.
1.+1.8V; VHT; VNBSB; 4.C_HTREF_NB_R; 5.C_14M_NB_R; 6.C_PCIEGFX_NB_R
NB voltage, frequency
NB_PWRGD
Measure the NB_PWRGD, and found it is low. M2A-VM’s NB_PWRGD is generated from VRM’s ASIC_CPUPWRGD. IO_PWROK (namely NB_PWRGD, SB_PWRGD) come from SIO, and is sent to SB, then the SB send out the various RESET# signals. On the M2A-VM, the SB_PWRGD and NB_PWRGD come from the same signal.

7. All dots RSTCON#, SB_PWRGD Solution:
Measure the PANEL PIN: 17 RSTCON#(this signal should be above 3V). This signal connect to SB directly. Here the NB_PWRGD should be high. If the SB work well, the SB would send out various RESET# signals PCI_RST#, IDE_RST#, IO_RST#, BIOS_RST#, CPU_RST#, etc.
Well, we found the NB_PWRGD is controlled by 1.2VHT, ASIC_CPUWRGD and O_RSTCON#, and convert to NB_PWRGD & SB_PWRGD via Q18 and OQ21. Meanwhile the SB_PWRGD & NB_PWRGD are also controlled by PSON#.
Solution:
Measure the OQ21 & PQ810’s PIN: 1. If the all of them are low, these signals’ status is correct. We focus on the load of NB_PWRGD, for example, SU1, SC70, OQ21, PQ8101, NU1, etc. Remove the components SC970, OQ21, PQ81 in turn until the failure vanished.
Chang a new PQ810, and reboot. Then the board is fixed.

8. All dots
Notice :
The example above is not a standard way to repair “all dots” solution. It is just a example.

9. “00” What is “00”? There are two kinds of “00”:
CPU doesn’t work, because there are not VCORE voltages, CPURST# or CLK, etc. Some failure caused by SB or NB’s bus halting.
The other condition is that CPU has worked, but it is halted, cause of losing data or address in translating.

10. ”00” How to confirm this kind of problem
Visual Inspection to check whether the board or components are damaged. Check whether there is trace broken.
Visual Inspection
Measure the frequency of crystal resonator, and check the voltage of “3VSB”.
Measure “3VSB” and KHz
Put on the CPU & Port 80 card, then power on. “FF” display on the card. Then put on the DEBUG CARD, “00” display on the card.
Put on debug card

11. “00” Example - P5VD1-X “00”: Visual Inspection “00” confirm CPU_CLK,
Measure the VCORE voltage, CPU_CLK and CPURST. The VOCRE should be 1.5V, the CPU_CLK should be 100MHz, and the CPURST# should be above 1.2V. When assert the RSTBTN#, their voltage should be changed, and then restore normal status promptly.
“00” confirm
VCORE 1.5V
VCORE is OK.
CPU_CLK is OK.
CPU_CLK,
CPU_CLK#
We found the CPURST# is only 0.3V, and when we assert the RSTBTN#, CPURST# didn’t change. So we can judge that it belongs to first condition of “00”.
CPURST#
There is no CPURST#. CPURST# is translated form SB to NB, then NB to CPU. So, SB & NB’s running voltage and frequency are necessary.

12. “00” NB’s frequency, HCLK, HCLK# 100MHz
Measure the voltage of NB circuit:
VTT_CPU is 1.2V, VTT_DDR is 1.25V. All of these voltage are OK.
NB’s voltage, VTT_CPU, 1.5V, VTT_DDR, 1.5VSB
1.5VSB is only 0.3V.There are two kinds of possibility.
1. Q23 burned，so there is no 1.5VSB voltage sent out.
2.Load is too big, make the 1.5VSB voltage to be low. (For
example, the load IC is burned, make the impedance
very small between VCC and GND).
Solution:
Measure the impedance between emitter (1.5VSB) and GND.
1.5VSB and
LAN IC
And the value is 10 ohm. So it looks like the load is too big. Then we short the Q23’s PIN2 and PIN3 (namely, 3VSB and 1.5VSB) for a while. Found that the U30 (LAN IC) is hot. So we confirm that the LAN IC is destroyed.
Change the LAN IC and Q23, reboot again. Fixed.

13. Thank You!