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Power Good Signal  

post #1 of 24
Thread Starter 
I am using a power supply tester and it has a rating for the Power Good signal. I am unfamiliar with what this rating should be at. Most power supplies tested are around 350ms I believe. I have an Ultra whos PG is 990ms. I am wondering what effects a High PG and a Low PG have on a system.
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post #2 of 24
Thread Starter 
Yeah... info is hard to find about this....
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post #3 of 24
Are you talking about the Green wire on the 24-pin plug?
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post #4 of 24
Thread Starter 
Dunno about the green cable, I am using a tester that reports the PG. It measures it in milliseconds. I think I remember that a good value is 350-400 or so but I do not know what the ramifications are for it being too high or too low.
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post #5 of 24
No. Power good is the gray. It's not the power on.

You're fine. PG is just a signal and all the Power Good signal does is tell the motherboard that there's DC power ready for the motherboard to use. Essentially, the PSU "brings up" all of the DC voltages and then the PG signal is shot to the board.

A longer delay on a PG just means the PSU is allowing more time for the voltages to be ready.

A short delay could be part of the reason 8800GT cards report that they're not getting enough voltage from the PCIe connectors.
post #6 of 24
Quote:
Originally Posted by jonnyGURU View Post
A short delay could be part of the reason 8800GT cards report that they're not getting enough voltage from the PCIe connectors.
Wouldn't adding a capacitor on the Power_Good line be enough of a delay?

Why are PSUs sending the Power_Good signal when they aren't really ready?
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post #7 of 24
A resistor would probably only lower the voltage, not delay the signal.

Not sure why anyone would want to shorten the delay. It would make sense to me to make that delay as long as possible.
post #8 of 24
Quote:
Originally Posted by DuckieHo View Post
Wouldn't adding a capacitor on the Power_Good line be enough of a delay?

Why are PSUs sending the Power_Good signal when they aren't really ready?
Probably depends on the capacitor...

Is there some sort of electrical gate that snaps open when the 12v line actually reaches 12v, or is it just driven by a capacitor as Duckie suggests? I'm curious to know more about how this works?
post #9 of 24
Quote:
Originally Posted by SgtSpike View Post
Probably depends on the capacitor...

Is there some sort of electrical gate that snaps open when the 12v line actually reaches 12v, or is it just driven by a capacitor as Duckie suggests? I'm curious to know more about how this works?
Yes, there are. However, a cap would be simplest way of doing it. Also, I am not sure the signal voltage is 12v.


Quote:
Originally Posted by jonnyGURU View Post
A resistor would probably only lower the voltage, not delay the signal.

Not sure why anyone would want to shorten the delay. It would make sense to me to make that delay as long as possible.
Capacitor.... not a resistor.

For layman, a capacitor would stop voltage from flowing through the line. However, the voltage starts to "leak" through as the cap charges. Once the cap is full, the full volage goes through. This should work for a constant DC signal and there is a threshold voltage for the signal on the motherboard.
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Once again...
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Hard DriveOSMonitorKeyboard
Intel X25-M 160GB + 3xRAID0 500GB 7200.12 Window 7 Pro 64 Acer H243H + Samsung 226BW XARMOR-U9BL  
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post #10 of 24
Quote:
Originally Posted by DuckieHo View Post
Yes, there are. However, a cap would be simplest way of doing it. Also, I am not sure the signal voltage is 12v.

Capacitor.... not a resistor.

For layman, a capacitor would stop voltage from flowing through the line. However, the voltage starts to "leak" through as the cap charges. Once the cap is full, the full volage goes through. This should work for a constant DC signal and there is a threshold voltage for the signal on the motherboard.
So a capacitor at say, 3.3v, could be put on the good power line. It would need to be sizeable enough to take at least as much time to charge as the caps on the 12v line... the 12v caps are what keeps the 12v power from being immediately available, right?
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