Diablotek is not a brand you will find being recommended here, oh wait, yes... you will find recommendations to "Replace ASAP". They are considered near, if not at, the bottom of the barrel as far as quality. This review of the PHD650 unit may be enlightening
http://www.hardocp.com/article/2010/12/17/diablotek_phd650_650w_power_supply_review/9#.Uq_cyozTlhE (linked to conclusion page). It is the only legitimate review I found of any Diablotek PSU's and is rather scathing (which is why I didn't reprint the main points here)
As far as the setting on the back, it depends upon your AC service but I can guarantee you've got it right because; if you're in the US and you select 230v, your PSU will fry whereas if you're in the UK (or other 220v service area) the PSU will not work with the setting of 115v. If in the US, use the 115v setting, most other countries use 230v setting but rather than doing that, I'll suggest simply replacing it with a higher quality unit from a brand such as Antec, Corsair, Enermax, PC Power & Cooling, SeaSonic, XFX or other well received brand/unit - legitimate reviews for many PSU's can be found through this link
http://www.realhardtechx.com/index_archivos/Page541.htm