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| Thread ID: 40907 | 2003-12-23 08:18:00 | ATX Power Supply PowerOn Trigger | george12 (7) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 202478 | 2003-12-23 08:18:00 | I have an ATX computer (quite new, Celeron 300Mhz) which won't turn on. Nothing happens when you press the power button. The power supply is not the problem, I have bought a new one with no difference. The problem is the PS-ON signal (Pin 14 on the motherboard plug) is not signaling. For the power supply to be on, the PS-ON wire must be < 0.8V. To be off, open circuit or > 2.0V. I have cut the wire to see with a multimeter what voltages are present, and found that on the motherboard side it is ~4.5V and ~3.5V on the powersupply side. When joined as normal it is ~4.5V. If I short the wire to ground, the power turns on, but I have heard that this is bad for the power supply. Please help, I am close to getting it going it is the best PC I own. |
george12 (7) | ||
| 202479 | 2003-12-23 09:02:00 | >(quite new, Celeron 300Mhz) how can a 300mhz celeron be NEW ???? have you tried just hitting the reset button? check ram, some boards won't run if ram is faulty. what voltage is the standby wire? |
tweak'e (174) | ||
| 202480 | 2003-12-23 09:43:00 | Is the +5Volt standby voltage, on pin9 OK? | Pheonix (280) | ||
| 202481 | 2003-12-24 00:22:00 | Those voltages on the wire are probably correct . The PS side is ~3 . 5 V . . . that's the "floating high" voltage of TTL logic . (I'm assuming you measured with a digital meter, with megohms of input resistance) . The MB side should have 5V from the 5VSB supply, which is on all the time the PSu is plugged in . 4 . 5 is low, but since it pulls up the PSU side when connected it's probably OK . The turn-on is accomplished by pulling that line to ground as you have discovered . A momentary pulse will do it, I think . That won't harm the supply, except by causing it to function as usual, and eventually wear out . ;-) I suspect the switch, or its connections . It should have three wires boing to it . . . +5V from the MB (using the +5VSB from PSU) on one side , the control wire (the centre connection) which eventually goes back to the PSU, and GND on the other side . The switch should normally hold the control lead at "5V", and go to "GND" when pressed . |
Graham L (2) | ||
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