There are 4 DIMM modules. I forgot to list that we tried that, sorry. The diagnostic lights are all blank, which according to the manual indicates no power. This is a new power supply we are using.

Does it do the same thing with the original power supply? Did the replacement power supply come from another 840? The only part that has not been replaced is the processor, but the symptoms sound like a power or motherboard issue, but those parts have been replaced. Have you tried it with a different power source?

Hi Tech177,

How many DIMMs are in the system? Try using just a single DIMM and see if there is any change. Also if you remove the front panel there are four diagnostic LEDs that show the current status and may be able to tell us where in POST it is stopping. What lights are lit and what color are they?

ftp.dell.com/.../poweredge-840_Owner%27s%20Manual_en-us.pdf page 43

We ordered a new power supply from online. We tested with both power supplies in the case. The thing with these power supplies is, they have a larger output than any i have seen before. We used a power supply tester to check both. The test came back with a high "PG" reading. The wall socket is on a workbench power strip, other computers run off the same plug fine.

Dell NPS-420 AB E

The PG rating is for “Power Good” It is what sends the signal to the processor that the power is correct and that it is safe to boot. If this is reading high it could mean that there is a voltage issue and that it is telling the CPU that it is not safe to power on. It is a 5V signal that is sent. Which model/part number power supply are you using?

That power supply model is the one that shipped originally with this server, so there should not be any issue with it working properly. We can try resetting the nvram on the motherboard and see if that helps.  ftp.dell.com/.../poweredge-840_Owner%27s%20Manual_en-us.pdf Page 116, but if it is the high PG rating causing it and it is occurring on both power supplies it sounds like an input voltage issue. Unless you are able to swap the processor with one from another system we can’t rule that out as the issue either.  

I reset the nvram, no change. according to the manual, there should still be a light code for CPU problems. Does that rule out the CPU?

That’s right that there should be a status for a CPU problem, and it doesn’t seem like one, however if all of the other parts have been replaced with the exact same outcome it is unlikely that it is the other parts that have been replaced already. As they are giving the exact same symptoms. You can also try disconnecting the control panel cable from the motherboard and see disconnect and reconnect power and see if it powers on, the power button or power on signal could be the problem as well. Do you have another 840 that you can test with?

We replaced the CPU with a Pentium 4, no change. We have only the one PowerEdge 840.

That rules out the processor as the issue. It sounds like it powers on, so it probably is not the system control panel, or it would not turn on at all. Does your test bench have a UPS or is it straight into the wall?

Our entire power system goes through a large UPS. all the other computers are running fine.

Interesting thing, i just plugged in a network cable, the NIC lights light up like normal.

If you have nic lights that means that the motherboard is getting power and activating the pci bus. Is it pingable? You took out the RAID controller with all of the other PCI cards right?

Yes, no other cards are installed. it is not pingable. I used angry IP scanner to try and find it. Another strange thing happened. I took the PSU out for more tests. One tester says the PG signal is "HH" or too high, a different tester says it is fine at 270ms. When i reattached the PSU, the back fan spun up, then stopped. It happened for 3 more attempts then stopped.