so like I said here in the beginning the psu is bad.
as to what else is wrong you can not tell until you get a new psu.
once you get a new psu do not attach to the mobo.
just test it with the little black tester the mobo cable and the power cable.
once it works (95% chance it will work) do not do any thing come back here and tell us it passed.
I will give you a step by step test method with photos.
@philipma1957
I'll come back and tell you once test is passed with new product. FYI, I've tested current PSU before connecting components to it and it has acted very well with built-in tester. But it died later, as I stated.
Shall I downgrade the circuit breaker back to Siemens B25? Remember I've upgraded it to Siemens B32 without upgrading cables. Due to building is 25 years old, it is difficult to change cables. Maybe I should create a new electrical line through wall but not sure what would be the best way to do it. I belive it will be impossible to use existing tunnels as they are very tight.
The same problem being the breaker in your fuse boxes blows?
It is tripping breaker, nothing like blow. Once I turn on breaker, breaker is working again. But PSU is tripping it even with only PSU tester is attached.
Did you buy this psu in a rig or separately?
I've bought PSU from an online store. Other components from different store. The box was unopened and I can tell, product was unused. Unless it was refurbished.
@stoniestfool
If you bought this in a rig perhaps the seller used refurbished psu's to save cost. The psu is definitely bad if when you tested it by itself it blows the fuse. At that point if working correctly the psu is pulling almost no power. I see you were using power save bios so my assumption you must be pulling more than 1200 watts was wrong.
Correct, I also have kill a watt and I'm pretty sure 5 cards was pulling around 800 watts. Even with 6th gpu I should be pulling around 950 watts. I'm using another computer to mod bios of gpus before connecting them to new rig.
The rig was mining before you tried the 6th card?
Yes, it was hashing ETH using Claymore and my hashrate per gpu was 29.3 using modded bioses.
When you are testing with the psu tester are all the other cables disconnected? Of course the 24 pin must be connected or maybe not if the tester plugs directly into the psu.
PSU tester is attached to mobo cable. So nothing else was connected while testing PSU after issue.
If you still have the gpu cables connected to the psu but not the gpu's. I am wondering if you pulled to much power on 1 of the gpu connectors. This would cause the wires to get hot enough to melt the coating. Then underneath the sheath the individual wires would be touching. That would be a short and cause this problem.
Most likely due to a short this issue is happening. But I'm not an expert so I'll be following suggestions posted here.