Orange lights on power on (board problem)

I also read in another discussion thread somewhere that there is also the Raedon RX6400, which has 4GB GDDR6 and uses 45W. I have this in my 9020SFF. You could probably get away with the stock 255W PSU, but I played it safe got the 315W version out of the XE2. The exact card I have is the Sapphire Raedon RX6400, which after looking on Amazon, there's not much difference in price, compared to the GTX1050.

The CPU I have is i7-4790 CPU @ 3.60GHz 3.60 GHz

Now once it's said orange lights matter - following Dell support I have to replace motherboard, not memory or PSU? Reseating CPU will be too much hassle for me, also this will void warranty 100% I think.

Problem that warranty was just 1 month. The problem occurred pretty soon after purchase (but not immediately), but I spent much time trying to fix that by software methods (thought it's Windows 10 issue, first)

One thing that still confuses me - is that Dell support says to replace motherboard, but no one on this forum says to replace motherboard...

255w PSU is the one that comes with 9020 SFF.

Not meant to be confusing, but I'm also in agreement with @redxps630 that it's the PSU.  Except for orange blink code, as for functionality, or lack thereof, that's where the signs have been pointing.  Up to you if you want to try replacing MB; however, PSU's go more often than MB's.

GTX 1050 Ti will still work great with the i7-4790 with only 2.9% bottleneck.

Didn't the PC already pass a hardware check, which doesn't check PSU?

Also, with PC off, but plugged in, push test button on the PSU.  Do this with all external peripherals disconnected.  Does it give you the green light?  Then all other internal peripherals are good.  Chances are when the test button is pushed, the fans will whirl up.  A bad PSU can still do that.

If no green light - there's the Dell BIST (built in self test).  How to Run a Power Supply Unit Self Test On a Dell Desktop or All-in-One Computer 

Dell BIST Test Video 

So if still in doubt, there's an option for ya'.  Like red, I still think it's the PSU though.

Yup, agree here. And I will add one more thing: Any warrenties on the 9020s are long expired by now, so no need to worry about voiding anything

This can be a powerful machine, since it has the i7-4790 - the maximum it can take, assuming the replacement PSU will fix the problem (after reading this thread, I'm about 98% certain it's the PSU) 

The 9020 was bought refurb.  Any warranty we were talking about would be from Amazon or one of their marketplace vendors.

Thank you very much for replies guys!!!
I'll run the PSU tests suggested by bradthetechnut once I find some free minutes (need PC to be on most of time)
Really appreciate all the help!

Amazon and others also have PSU testers.  But then you'd also end up needing an adapter.  MB connection in 9020 is 8-pin instead of standard 24-pin.

May I ask what would be approximate price of tester+adapter?

PSU Testers on Amazon 

i couldn't find the right adapter though.  On Amazon and I Googled "24-pin male to 8-pin male adapter."  I couldn't find one.  Normally, those things are male to female for adapting PSU's to MB's.  May be @redxps630 or another will know something about those adapters and applying them to an 8-pin female PSU for PSU tester.

If I have it right, 8-pin male plug would plug into PSU and 24-pin male would plug into tester.  May be it doesn't work in reverse.  Because one can adapt 24-pin PSU to 8-pin MB, but not the other way around.  Can't use an 8-pin Dell PSU and adapt it to a 24-pin MB.

Hopefully I didn't cause any confusion.  There it is.

I would not recommend buying psu tester + adapter unless you are doing this on regular basis as a hobby or profession.  Gamers nexus has such a tester n they make $ on it by showing their test results of various makers psu.  It does not sound like OP is like such a person or into that field.

the cost of such a tester likely far exceeds that of a new 315w psu oem readily available now ($45 free shipping).

https://www.ebay.com/itm/Power-Supply-Unit-For-Dell-Optiplex-XE2-9020-7020-3020-SFF-VX372-315W-D315ES-00/294919337602?hash=item44aa8ff682:g:W0gAAOSwr99iVNLY&amdata=enc:AQAHAAAA0DtbKa4HaI7qpTT0gkHhZidRD1CeGWwjWsdb+Ctq1BrPf1z4s5F9DKgTpM5lOoJxkDBpSS8iKRMG6diCYpXZjjS/QFhH3KUtdWvStq5OwX+ty4Btxoed463Mb8j3xqbCCK0AysT5SQiLiby3PyW95zzwf5uTLicSigR60C7fu7kjE8R8JbPGOPoOSBggoi4cvEEW8ccEaCLXr0uDptcQzewL9OkHAZQbrdBsikcRCDQumNsAhcx2XWUduf9vDT7VnseZ2WrwJUSM6igDjIDoo90=%7Ctkp:BFBM4q6wqP5g&pageci=f6e28637-3621-401b-8cf8-5ffb69ab67c0&redirect=mobile

$14.99 PSU tester does not far exceed $45.11 PSU. 

As for PSU testing, the caveat being is doesn't look like the needed adapter is made, and may not work even if it were.  I'll just have to remember to not mention PSU testers for PC's with 8 & 6 pin PSU's/MB's until I see anything different.

If I ever want a deal on a PC here in the U.S., I'll have to ask @Chino de Oro.  : )

Always welcome Brad, check your pm.