Question : Problem: PSU with 990ms PG value on tester

I have just bought a Thermaltake Toughpower 1500W PSU, and a PSU tester.

When run the test, only the PG value on the LCD screen of the tester blinks and shows 990ms, anyone knows if there is a problem of this PSU? Is the problem serious that I should not use it?

(The tester is proven fine as it stays quiet for my other PSU)

Answer : Problem: PSU with 990ms PG value on tester

Yes, the PG value (also known as Pwr_OK), is simply a signal to the motherboard that the supply voltages have stabilized -- or, as you said, a measure of how fast the PSU is ready to provide power.   It is not used for anything else ... and has no impact on the operation of the system.   Once the voltages have stabilized and Pwr_OK is asserted, the circuitry on the motherboard starts the boot process ... and as long as the actual voltages are all okay, the PSU will work fine.

... it IS, however, out of spec => as you've noted, the other unit asserts in 320ms (well within the specification).   But it won't "burn out" anything on the system as long as the voltages themselves are all okay.