my HP Z400 (With upgrades) won't start

[Metti93]

From the office I could take four old workstations with me. These are the HP Z400 workstations.

I have expanded the largest RAM sticks out of three workstations, then packed them all into one.

Windows packed onto a SSD and boom, I had a great computer.

Now I wanted to install a stronger GPU, a RX 580. but this requires more electricity. an 8-pin connector and no 6-pin, as with the HP power supply.

That's why I bought a new ATX power supply.

But after I realized that the pinout is different at HP (for reasons I do not want to understand), I had to tinker the whole thing.

 

Now I get instead of 4 "Beeps" Diagnostic LED Codes, 5 "Beeps".

According to the website, https://support.hp.com/us-en/document/c03599666, I have to check the RAM. 
After I have tried out all the combinations, everything except for one stick, two sticks, another line of the Rhine. I doesn't start.

Can someone help me there?

[Fasauceome]

4 minutes ago, Metti93 said:

That's why I bought a new ATX power supply.

But after I realized that the pinout is different at HP (for reasons I do not want to understand), I had to tinker the whole thing.

you altered your power supply's connectors? in what fashion?

[aisle9]

https://www.moddiy.com/products/ATX-to-HP-Z400-24%2dPin-Non%2dStandard-ATX-Pinout-Main-Power-Adapter-Cable.html

 

HP (and most brands now) use custom PSU connectors on their motherboards because...well, because they're assholes. You need an adapter to make an aftermarket PSU work.

[Metti93]

1 minute ago, aisle9 said:

https://www.moddiy.com/products/ATX-to-HP-Z400-24%2dPin-Non%2dStandard-ATX-Pinout-Main-Power-Adapter-Cable.html

 

HP (and most brands now) use custom PSU connectors on their motherboards because...well, because they're assholes. You need an adapter to make an aftermarket PSU work.

Thanks for your quick feedback.

But that's not the problem. If I wire the power supply incorrectly, it will give me an appropriate error code in the format of a whistle anyway. I have fixed that for a long time.

It's all about the error code that handles the RAM.
And there too, I do not really know what he wants from me.

[Johnny Relentless]

So power cable is connected correctly ?

You cleaned it up physical?

There is no way of entering bios right ?

 And now worstcase scenario ! Did you installed the cpu urself ? Check for broken or bended pins

[Metti93]

In a nightmare last night, I was able to find the fault. The one 12v cable I did not crimp correctly, and thus the whole system was not properly powered.
Now the workstation is running perfectly.

make a few benchmarks.

Thank you very much for your suggestions!