Only posts using wiring harness

[Erick]

I have a Dell Inspiron 3847 with a MIH81R mainboard in it.

Moving the mainboard to a new case with a new power supply. There's a harness in the old machine for the power switch. Not a problem, got everything set up in the new case, I mapped the two jumpers and plugged in the two leads from the power button on the new case.

CPU fan turns on but the mainboard won't post.

Seems weird so I pull the whole harness from the old case and plug it in. Push the power button on the other end of the harness and the mainboard posts with no issue.

Am I missing something here? In every machine I've been elbow deep in I could get it to crank over using a paperclip touching two jumpers. Is there something odd about this where powering it up is proprietary?

 

[GTP]

Have you connected the mainboard/CPU power plug?

 

[Erick]

Have you connected the mainboard/CPU power plug?

Good call!

Yes, yes I have.

Literally, if I plug in the wiring harness it posts. Unplug the harness and run a paperclip across the two posts that the power button goes to and the CPU fan starts but it doesn't post.

 

[frase]

Checked RAM - one module first
Pop out CMOS battery to reset and try again.

Still may be a CMOS jumper onboard that can be set on/off - this usually kicks niggly mobos into action.

 

[mr m]

In every machine I've been elbow deep in I could get it to crank over using a paperclip touching two jumpers. Is there something odd about this where powering it up is proprietary?

Does the connector on the MOBO that the power switch plugs into contain only two pins or is it a multi-pin header? I am betting there is more to this circuit than a simple two wire switch and that you are correct about it being proprietary.

I have never seen this before. Like you say, I have always been able to short out the two pins on the MOBO to check for a defective on/off switch.

 

[Krynn72]

Post a pic of the harness. Curious if its got any sort of PCB or in-line components soldered into it. Very strange issue.

 

[Erick]

Does the connector on the MOBO that the power switch plugs into contain only two pins or is it a multi-pin header? I am betting there is more to this circuit than a simple two wire switch and that you are correct about it being proprietary.

I have never seen this before. Like you say, I have always been able to short out the two pins on the MOBO to check for a defective on/off switch.

That's what I think I'm discovering.

It looks like pins 1, 2 and 4 are connected on the harness. and in slot 4 there are two wires. To say it another way, there's a wire in the harness that goes from 1 to 2 and then to 4 and stops. In 4 there's one of the leads from the power switch. The other lead goes to 12.



The power switch has wires coming out of it that are Blue and Brown. And from the harness port where the Blue wire goes there's a black wire (denoted as Black 1) that goes to two other ports on the harness.

So...that begs the question.....how do I rig this up to work with a standard power switch?

 

[Erick]

Post a pic of the harness. Curious if its got any sort of PCB or in-line components soldered into it. Very strange issue.

Let me know if the schematic I posted above makes sense. I've taken a few pictures but it doesn't seem to really convey the whole of the component, if that makes any sense.

 

[nlinecomputers]

It is a dell it is almost certainly a proprietary switch. Most Dell headers also have the POST code lights and other non-standard goodies. WHY are you moving this to a different chassis?

 

[Erick]

It is a dell it is almost certainly a proprietary switch. Most Dell headers also have the POST code lights and other non-standard goodies. WHY are you moving this to a different chassis?

Original case is too small to accommodate the video card the user wants to install.

And yes, it is a Dell.

 

[Markverhyden]

Post a pic of the harness. Curious if its got any sort of PCB or in-line components soldered into it. Very strange issue.

It is a dell it is almost certainly a proprietary switch. Most Dell headers also have the POST code lights and other non-standard goodies. WHY are you moving this to a different chassis?

My thoughts exactly. Those big OEM's do everything they can to steer customers to purchase/use only their branded stuff so it would be no surprise if it was chipped, etc. See this all of the time with laptop AC adapters.

 

[mr m]

So...that begs the question.....how do I rig this up to work with a standard power switch?

First off let us agree on the pin outs. We do not know which is pin 1 without a schematic so lets call the top left pin in your diagram #1. That makes the three black(1) wires going to pins 1,3 and 7 with pin 7 also containing the blue wire from the original switch.

One way to connect the wires to the pins is to find an old 4 wide, single row connector that you can cut up to fit across pins 1,3,5,7. Cut the connector leaving a couple of inches of wire to solder to. Solder the three black wires to the cut leads corresponding to pins 1,3 and 7. Now solder on of the two wires from the new switch to those 3 connected black wires. Connect the second lead from the new switch to pin 8 or where the brown wire is in your diagram.

So you end up physically connecting pins 1,3,7 and one of the new switch wires together and the other switch lead to pin 8.

These extra wires in the power on/off circuit might be a proprietary system to tell the PC what to do after an AC power disruption.

 

[mikeroq]

Based on what I can gather the connector looks like this:

You need to replicate the bit that has the jumper.

Like this:

Myself I would cut off the old connector and wire up the power, hdd led, and power led to a 2x3 2.54mm crimp connector housing with male pins. Then plug the cables from the case into my new header extension.

 

[Diggs]

Sigh...... I try, but I still don't like Dell...... They keep shooting themselves in the foot on so many levels.

https://www.technibble.com/forums/threads/dell-shaking-head-sadly.74953/