Dell Z420 Workstation Powers On But No Output

[smarmar]

If anyone can supply some help, much appreciated. I've acquired a Dell Z420 Workstation released around 2012, similar to the specs on this one:
https://support.hp.com/us-en/document/c03277050

It powers on; the lights on the front panel, the motherboard, power supply, and keyboard come on but there's no signal going to the monitor. Although the keyboard lights up, none of the lock lights come on when I press the keys. All of the fans start at a low speed when the computer powers on but then after about 30 secs speed up balls to the wall (including power supply fan) I know the monitor and keyboard work because I'm using them right now on a different computer. Here are the things I've tried:

1. Reseating the 3 RAM sticks and seating 1 stick at a time to see if the mb beeps. It beeped only when there was no RAM seated.
2. Visually checked capacitors for bursts or swelling.
3. Replaced coin battery.
4. Replaced HDs with one(s) that I know work.

" alt="" class="bbc_img" />
5. Disconnected everything but 1 HD, 1 fan, 1 RAM stick, and a keyboard to make sure the power supply wasn't overworked. I would've replaced the power supply but I don't have one with the correct pin configuration for the main mb power socket (labeled in attached photo).
6. Replaced the 2 GPUs with one I know works. There's no onboard GPU, which is normal for most workstations.
7. I tried getting into the BIOS but either the keyboard inputs aren't recognized or maybe the mb is bad.

[smarmar]

Edit: It's an HP, not a Dell.

I found a 24-pin to 18-pin adapter for the main mb power socket, so now I can test it with another power supply. 

[Tactile]

Is there a chassis intrusion switch somewhere?

[smarmar]

I see where one should be installed on the case but there isn't one there. Good question though. I didn't think about that.

[tp4tissue]

reseat cpu.

if the back doesn't have vga,  use just 1 card, make sure it's in the primary slot.

on some boards power on might take a while, my server boards take a couple minutes.

[smarmar]

Dear tp4,
There are no VGA ports on GPU, nor integrated video ports on the case.
I disconnected one of the GPUs and left the remaining one in SLOT1.
I let the computer run for 5 minutes but nothing came up on the monitor.
Reseat the CPU? Yikes! I don't have any thermal paste, if that's what is required. I lack experience in those matters. I guess I have nothing to lose, eh?

[tp4tissue]

Dear tp4,
There are no VGA ports on GPU, nor integrated video ports on the case.
I disconnected one of the GPUs and left the remaining one in SLOT1.
I let the computer run for 5 minutes but nothing came up on the monitor.
Reseat the CPU? Yikes! I don't have any thermal paste, if that's what is required. I lack experience in those matters. I guess I have nothing to lose, eh?

you don't need new paste, yes that's preferred, and you will buy some in the future, but for purposes of testing in the short term, it's unlikely that you will be in an overheat situation.

just leave whatever paste is on there, or if it's still gooey enough scrape it towards the middle before you put the heatsink back on.

don't wipe any off

[Darthbaggins]

Considering the rig's age, I have a feeling a section of the CPU (that controls the PCIe slots) has gone out.  I would also try clearing the CMOS - pull the battery and have the rig disconnected from the power coming from the wall.

[tp4tissue]

Considering the rig's age, I have a feeling a section of the CPU (that controls the PCIe slots) has gone out.  I would also try clearing the CMOS - pull the battery and have the rig disconnected from the power coming from the wall.

also check for cmos jumpers in case the board is ol'skool,

[Leslieann]

Check for blown caps but odds are it's a bad cpu or mobo, most likely the latter.

[smarmar]

I found the CMOS reset button on the mb and held that down for 20 seconds with the power cable disconnected. I also found a jumper nearby and did the reset on that. Not sure if it was for the CMOS but did it anyway. I tried connecting a different PSU but I think I plugged something in that wasn't compatible. A red light flashed on the mb and the computer beeped repeatedly.
Oh well, I tried. I'll keep the case and maybe build it out with another mother board and GPU or something.