New graphics card not working

[Fibonacci82]

Hello everyone, I just purchased a HP EliteDesk 705 G4 with a Ryzen 7 2700 and I was attempting to add a Radeon RX 6400 graphics card. If I put back the graphics card that came with the computer, it runs fine.I have two other G4 with Rzyen 5 3400 and they accept the Radeon RX 6400 with no issues. I have tried enabling and disabling the legacy boot and have disabled, the securilock in BIOs. The PC will run for a few seconds, all the fans are spinning, and then it will shut off and restart, and it will continue to do that until I turn it off. I have updated the BIOs with no results. This motherboard seems to be slightly different than my other G4 it does not have a functioning integrated graphics card on the motherboard. This is the second computer with the same motherboard that I purchased. I bricked the first one by disabling the PCIE slot and with no integrated graphics card, it just gives six beeps which indicates a problem with the graphics card. With no display, I have no access to bios. I also tried to replace the motherboard only, but could not find any online. The motherboard part number is L35845-001. Any help would be appreciated.

[BeemerBiker · Accepted solution]

The RX 6400 requires minimum of 250 watt power supply.  I assume you have the 400 watt option or the 250 watt 

If you have the 250 watt supply it may be overloaded.  if the BIOS had the option to delay starting the disk drives then select something like a 10 second delay to prevent a power surge.  Just guessing.

What graphics card came with the system that works if you put it back?

Compare your Radeon RX 6400 to the other ones and to the images shown in the link above.  

I once bought a fake GTX-1050Ti on ebay and was luck I was able to return it.

Try the new card on one of your other systems.

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@Fibonacci82 wrote:

 bricked the first one by disabling the PCIE slot and with no integrated graphics card, it just gives six beeps which indicates a problem with the graphics card. With no display, I have no access to bios.

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 Removing the CMOS battery usually reset the motherboard.

The  Ryzen 7 2700 does not have integrated graphics in the chip so you need a graphics card or a different Ryzen CPU