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I think it's a bad on/off switch, how can I tell?



 
 
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  #1  
Old June 1st 20, 03:13 PM posted to alt.comp.hardware.pc-homebuilt
Charlie Hoffpauir
external usenet poster
 
Posts: 342
Default 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  
Old June 1st 20, 03:51 PM posted to alt.comp.hardware.pc-homebuilt
Charlie Hoffpauir
external usenet poster
 
Posts: 342
Default 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  
Old June 1st 20, 08:53 PM posted to alt.comp.hardware.pc-homebuilt
Paul[_28_]
external usenet poster
 
Posts: 1,308
Default 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  
Old June 2nd 20, 01:11 AM posted to alt.comp.hardware.pc-homebuilt
Charlie Hoffpauir
external usenet poster
 
Posts: 342
Default 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  
Old June 2nd 20, 10:00 AM posted to alt.comp.hardware.pc-homebuilt
wasbit[_4_]
external usenet poster
 
Posts: 15
Default 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  
Old June 2nd 20, 03:52 PM posted to alt.comp.hardware.pc-homebuilt
Charlie Hoffpauir
external usenet poster
 
Posts: 342
Default 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  
Old June 2nd 20, 05:01 PM posted to alt.comp.hardware.pc-homebuilt
Flasherly[_2_]
external usenet poster
 
Posts: 2,312
Default 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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