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#1
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I think it's a bad on/off switch, how can I tell?
My computer won't restart after a local power failure last night. Our
neignborhood lost power for 7 hours, but the computer was on a UPS when we lost power. I shut it down with the power switch , but after power was restored, it wouldn't start. I thought perhaps the PS was fried in spite of the UPS because when the power went out, it didn't go out all at once, it "flickered, that is, on and off rapidly for several seconds. Anyway, I installed a old PS that I had used in another computer, but no effect. Now I'm suspecting the on/off switch on the case. There are 4 wires from the switch to a pin set on the MB, red, black, white, and green. Can someone tell me if it's possible for me to short two (?) of these wires to bypass the on/off switch, and thus see if indeed it's just a bad switch? And it that's the case, a way to simply bypass the case switch and get back in operation? |
#2
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I think it's a bad on/off switch, how can I tell?
On Mon, 01 Jun 2020 09:13:03 -0500, Charlie Hoffpauir
wrote: My computer won't restart after a local power failure last night. Our neignborhood lost power for 7 hours, but the computer was on a UPS when we lost power. I shut it down with the power switch , but after power was restored, it wouldn't start. I thought perhaps the PS was fried in spite of the UPS because when the power went out, it didn't go out all at once, it "flickered, that is, on and off rapidly for several seconds. Anyway, I installed a old PS that I had used in another computer, but no effect. Now I'm suspecting the on/off switch on the case. There are 4 wires from the switch to a pin set on the MB, red, black, white, and green. Can someone tell me if it's possible for me to short two (?) of these wires to bypass the on/off switch, and thus see if indeed it's just a bad switch? And it that's the case, a way to simply bypass the case switch and get back in operation? OK, I found out that it's just a bad power switch by unplugging the switch wiring from the MB and shorting two of the pins on the MB, and the computer starts up (on the bench, disconnected from everything). so now I'm going to try simply adding an external momentary switch, hoping that will do the trick. |
#3
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I think it's a bad on/off switch, how can I tell?
Charlie Hoffpauir wrote:
On Mon, 01 Jun 2020 09:13:03 -0500, Charlie Hoffpauir wrote: My computer won't restart after a local power failure last night. Our neignborhood lost power for 7 hours, but the computer was on a UPS when we lost power. I shut it down with the power switch , but after power was restored, it wouldn't start. I thought perhaps the PS was fried in spite of the UPS because when the power went out, it didn't go out all at once, it "flickered, that is, on and off rapidly for several seconds. Anyway, I installed a old PS that I had used in another computer, but no effect. Now I'm suspecting the on/off switch on the case. There are 4 wires from the switch to a pin set on the MB, red, black, white, and green. Can someone tell me if it's possible for me to short two (?) of these wires to bypass the on/off switch, and thus see if indeed it's just a bad switch? And it that's the case, a way to simply bypass the case switch and get back in operation? OK, I found out that it's just a bad power switch by unplugging the switch wiring from the MB and shorting two of the pins on the MB, and the computer starts up (on the bench, disconnected from everything). so now I'm going to try simply adding an external momentary switch, hoping that will do the trick. I've had a switch go bad like that. Possibly a dome switch with thin plastic cover. Whether a switch fails permanently closed or a switch fails permanently open, it's not going to work. The switch has to have both positions working, for the logic to be sequenced correctly. The Power switch needs both positions to work. The Reset switch on the other hand, if it's jammed ON, then the machine stays reset forever and will not boot. The screen won't light up in that case. An indication this is happened, is the NIC PHY doesn't autonegotiate with the router and the NIC LEDs may stay off too if Reset is jammed ON. You can leave your temporary momentary switch in position if you want. The machine I'm typing on, there's a switch hanging off the chassis right now :-) It's been like that for years. Only two wires are needed for a single switch. If the assembly has four wires, the plastics could contain a Power switch and a Reset switch. Where the X's are in the diagram, suggests how four wires could be arranged. You would think, logically, that the ground could be shared, and it only needs three wires, but they arrange the wire in twisted pairs, and four pins works better with two twisted pairs, during fabrication. PWR# +5VSB --- 10K ----+----X | +== Momentarily closed for Power GND--------------------X | RST# +5VSB --- 10K ----+----X | +== Momentarily closed for Reset GND--------------------X | The switch bodies float with respect to chassis. Generally, the switch body is not purposely connected to chassis, and in a lot of cases the switches are set in the plastic facade anyway. They like to make up twisted pairs for each switch (as a means to reduce capacitive transient coupling). Years ago, we had a box at work, where the Reset line worked as an antenna. If there was the tiniest ESD discharge into the external metalwork on the computer, the box would RESET on the spot. (I got a plane trip to observe customer symptoms first hand. The machines were quite sensitive.) My boss knew the layout of the wiring in the box (the managers did the chassis, the grunts did individual printed circuit boards), and he figured it out right away, that the two foot long wire stretched across the chassis inside, was a bad idea. That's his PhD in Physics cutting in. I'm not aware of any similar situations on PC chassis, so those twisted pairs must be working AOK. There are a few things about PC chassis design that defy logic, but you can't argue with success. Paul |
#4
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I think it's a bad on/off switch, how can I tell?
On Mon, 01 Jun 2020 15:53:59 -0400, Paul
wrote: Charlie Hoffpauir wrote: On Mon, 01 Jun 2020 09:13:03 -0500, Charlie Hoffpauir wrote: My computer won't restart after a local power failure last night. Our neignborhood lost power for 7 hours, but the computer was on a UPS when we lost power. I shut it down with the power switch , but after power was restored, it wouldn't start. I thought perhaps the PS was fried in spite of the UPS because when the power went out, it didn't go out all at once, it "flickered, that is, on and off rapidly for several seconds. Anyway, I installed a old PS that I had used in another computer, but no effect. Now I'm suspecting the on/off switch on the case. There are 4 wires from the switch to a pin set on the MB, red, black, white, and green. Can someone tell me if it's possible for me to short two (?) of these wires to bypass the on/off switch, and thus see if indeed it's just a bad switch? And it that's the case, a way to simply bypass the case switch and get back in operation? OK, I found out that it's just a bad power switch by unplugging the switch wiring from the MB and shorting two of the pins on the MB, and the computer starts up (on the bench, disconnected from everything). so now I'm going to try simply adding an external momentary switch, hoping that will do the trick. I've had a switch go bad like that. Possibly a dome switch with thin plastic cover. Whether a switch fails permanently closed or a switch fails permanently open, it's not going to work. The switch has to have both positions working, for the logic to be sequenced correctly. The Power switch needs both positions to work. The Reset switch on the other hand, if it's jammed ON, then the machine stays reset forever and will not boot. The screen won't light up in that case. An indication this is happened, is the NIC PHY doesn't autonegotiate with the router and the NIC LEDs may stay off too if Reset is jammed ON. You can leave your temporary momentary switch in position if you want. The machine I'm typing on, there's a switch hanging off the chassis right now :-) It's been like that for years. Only two wires are needed for a single switch. If the assembly has four wires, the plastics could contain a Power switch and a Reset switch. Where the X's are in the diagram, suggests how four wires could be arranged. You would think, logically, that the ground could be shared, and it only needs three wires, but they arrange the wire in twisted pairs, and four pins works better with two twisted pairs, during fabrication. PWR# +5VSB --- 10K ----+----X | +== Momentarily closed for Power GND--------------------X | RST# +5VSB --- 10K ----+----X | +== Momentarily closed for Reset GND--------------------X | The switch bodies float with respect to chassis. Generally, the switch body is not purposely connected to chassis, and in a lot of cases the switches are set in the plastic facade anyway. They like to make up twisted pairs for each switch (as a means to reduce capacitive transient coupling). Years ago, we had a box at work, where the Reset line worked as an antenna. If there was the tiniest ESD discharge into the external metalwork on the computer, the box would RESET on the spot. (I got a plane trip to observe customer symptoms first hand. The machines were quite sensitive.) My boss knew the layout of the wiring in the box (the managers did the chassis, the grunts did individual printed circuit boards), and he figured it out right away, that the two foot long wire stretched across the chassis inside, was a bad idea. That's his PhD in Physics cutting in. I'm not aware of any similar situations on PC chassis, so those twisted pairs must be working AOK. There are a few things about PC chassis design that defy logic, but you can't argue with success. Paul Thanks for your reply. In my "testing" to find out what might work, I determined the two pins on the MB that cause a stop or start. So I simply used the wiring from the chasis switch, and put an old momentary switch... mounted in one of the panels in the back where there was a cutout for another card, and it works fine. The original chassis switch had an "on" light built in, so that might have been what the two extra wires were for. I was a bit surprised to see that the wiring was 2 pairs and shielded. |
#5
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I think it's a bad on/off switch, how can I tell?
"Charlie Hoffpauir" wrote in message
... My computer won't restart after a local power failure last night. Our neignborhood lost power for 7 hours, but the computer was on a UPS when we lost power. I shut it down with the power switch , but after power was restored, it wouldn't start. I thought perhaps the PS was fried in spite of the UPS because when the power went out, it didn't go out all at once, it "flickered, that is, on and off rapidly for several seconds. Anyway, I installed a old PS that I had used in another computer, but no effect. Now I'm suspecting the on/off switch on the case. There are 4 wires from the switch to a pin set on the MB, red, black, white, and green. Can someone tell me if it's possible for me to short two (?) of these wires to bypass the on/off switch, and thus see if indeed it's just a bad switch? And it that's the case, a way to simply bypass the case switch and get back in operation? Common cure is to move the on/off switch wires to the reset switch & do without the little used reset function. -- Regards wasbit |
#6
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I think it's a bad on/off switch, how can I tell?
On Tue, 2 Jun 2020 10:00:03 +0100, "wasbit"
wrote: Common cure is to move the on/off switch wires to the reset switch & do without the little used reset function. .... would have, if there was a reset switch on this case. |
#7
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I think it's a bad on/off switch, how can I tell?
On Tue, 2 Jun 2020 10:00:03 +0100, "wasbit"
wrote: Common cure is to move the on/off switch wires to the reset switch & do without the little used reset function. Common is doing a case update after too many modifications, when encroaching tedium is looking at the old one because of what happens with the tin-snips and aluminum shears. Past ripe, cut out any potentially case electronics salvageable, and toss that into the big cardboard box, along with the rest, containing anything under the sun imaginable. Actually did that, even to once repair either a flaky RST or flittering PWR switch. Not that, mechanically, a case ought to take a particular rummaged item from another;- hanging it out a hole from somewhere off the case with wires works fine for function over form, though, when lacking a gamer case with $30 LED blinking fans. |
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