7020 mt psu upgrade not working

Question

Hello everyone.

This is my first post on the forums. I have recently acquired a dell optiplex 7020 mt (i7-4790) and want to upgrade the power supply, graphics card, ram and add an ssd. I have bought an

EVGA 500w 80+ white psu,

500gb sata ssd,

16gb of PC3-12800u ram and

an asus rx 580 8gb.

I have tested all the new upgrades (aside from the gpu) with the original power supply and things work as expected. However, when I install the new psu, the fans spin for a second before stopping and the power button flashes amber. I have used a 24-8 pin adaptor to connect to the motherboard (https://www.amazon.co.uk/gp/product/B0758H3WVX/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 ) and the 4 pin cpu connector. I have also tried with the gpu and tried different ram slots etc. but to no avail. Do I have a compatibility issue, is my power supply faulty or is there another issue?

Thanks in advance!

bradthetechnut · Answer

Possible compatibility issue with PSU.

To fall more in line with Dell PSU's, the PSU needs to have a certain amount of power on certain rails. It isn't just the total watts of the PSU.

Speedstep regularly recommends the EVGA 750 BR or B1-(expensive) or the 700 BR. But they are increasingly harder to find. When I Googled the item, Zoro was one vendor that came up, but they take up to 25 days to ship.

The backup suggestion is a Corsair CX 750.

A vendor that came up when looking those up is simylor, but they look too cheap, as in prices almost to good to be true. Could be knock-off or used items.

While the power requirement for your RX 580 is 500w, Dell's are their own breed. Best way I can put it.

If speedstep chimes in, he can give more details.

olukeph · Answer

Thanks for the information. That makes a lot more sense. Does that mean that it is the -12 and 5VSB rails that are under-supplied? It appears that the standard psu runs at 12w and 20w respectively. This seems very high, and even the psus that you recommend have lower wattages for these rails. Does that matter, and would 9.6w and 15w be too low to power the motherboard?

bradthetechnut · Answer

I only mentioned the PSU's speedstep recommends and what be uses for a backup suggestion.  Screengrab will have more info. Image will appear once approved by a moderator:

speedstep · Answer

EPS12v was updated due to problems.

This is why 90 to 130W combined is not sufficient for 3.3v/5v rails.

Dell actually upgraded that to 225W combined with 30AMPS for 3.3v and 32AMPS for 5v

5VSB is 20W aka 4 AMPS.

Power supplies only using WATTS total as a spec means you disregard what is going on with the other rails.

Thats why EVGA 750B1, 700BR works but the B2 B3 BQ W1 N1 etc versions from the exact same vendor do not work.

The only difference is the power on 5VSB and the Combined power and Amps for 3.3v/5v rail.

EPS12v SpecDell 875WDELL 850W used in Aurora Etc Modular with many cables

speedstep · Answer

3020 7020 9020 needs CAB359 adapter. https://www.moddiy.com/products/Dell-OptiPlex-7020-PSU-Main-Power-24-Pin-to-8-Pin-Adapter-Cable-30cm.html

olukeph · Answer

Thank you. So if I order the EVGA 700 BR I should be fine? Is my current adaptor not up to scratch or does it have to be dell own brand? I am in the UK so it would take a long time for the linked adaptor to arrive.