HP DC7700 No POST, No Display

[debugtimog]

Hi All,
I have an HP DC7700 motherboard with no POST and no display. I have swapped the CPU, reset the BIOS, and swapped the power supply ( i have 4 identical units) and still nothing.

Below is the measure voltages from the 24pin connector and the 6 pin connector when the power on switch was on and off.

I hope somebody can guide me on the next step to isolate what could have caused the problem. Thanks

[Techtiger]

Re: HP DC7700 No POST, No Display

Try to Flash Bios save your old first

[debugtimog]

Re: HP DC7700 No POST, No Display

saw this online, thanks techtiger. I will try this, more suggestions are welcome.

2. Hot Swap your BIOS chip and re-flash:

Hot Swapping is a technique used to flash bios using another similar motherboard. You need to have access to a exact same motherboard model (different models with same chip might work). I tried this method as well and I can confirm it works flawlessly! I wrote a separate post about how I did it. See below,

How I fixed my corrupted BIOS chip by Hot Swapping

3. Re-flash your BIOS chip with a chip writer ( Serial flash programmer)

This is a risk-free method and all you need is a Serial Flash Programmer. I tried both above methods and they work great, but I am a person who play with BIOS settings too often and end up corrupting sooner or later. So I needed a quick solution that let me fix corrupted BIOS instantly without spending anymore money or without bothering someone else to risk their motherboard for another hot-swap. So finally this 3rd method was the perfect method I've ever tried. I wrote a separate post about how I did it. See below,

[Techtiger]

Re: HP DC7700 No POST, No Display

To Flash corrupted BIOS Chip you need a Bios reprogrammed tool cost of this less than 10$ eBay China, you don’t need to remove the chip if you buy the clip socket

[debugtimog]

Re: HP DC7700 No POST, No Display

anybody have a diagram for this? if I want to check if north bridge or southbridge is ok, is there a signal I could measure?

[piernov]

Re: HP DC7700 No POST, No Display

Flash the BIOS first before anything.
Also a lot of those boards have garbage CapXon 470uF 6.3V capacitors. (I think the earlier revisions with Pentium D, not the Pentium Dual-Core/Core 2 Duo ones)

As far as I know, no schematics or boardview available.

[debugtimog]

Re: HP DC7700 No POST, No Display

i did swap the BIOS IC from the other good motherboard. the bad motherboard still did not POST and the good motherboard POST and there is a display. Is swapping BIOS IC equivalent to flashing?

[piernov]

Re: HP DC7700 No POST, No Display

Yes swapping BIOS IC is ok.
Did you check the capacitors?
What's the voltage on CPU Vcore? (can be measured between the coils next to the CPU and ground, or across the capacitors next to the CPU)

[debugtimog]

Re: HP DC7700 No POST, No Display

the capacitors are OK both on capacitance value and ESR(below 1 ohm). The Vcore, I think around 1volts something, not really sure, but I did compare with the other good motherboard and it is the same, thats why I dont remember exactly the value.