Xbox rev 1.6 still won’t power on after multiple fixes

[Cytra]

I’ve replaced the capacitors, I’ve checked the power cable, the PSU is good, the transistor has been replaced, it’s a 1.6 motherboard in a 1.6 case, I’m completely dumbfounded. I try to press the power button and get no error lights, no sound from the inside of the xbox, nothing. I see no charred spots anywhere on the inside either, so it doesn’t seem like anything is blown. Can I get some recommendations here? P.S. I’m a bit of a newbie when it comes to part names and locations, so keep that in mind.

[KaosEngineer]

Make sure that the power supply unit's 5Vdc standby voltage is present at the motherboard's power connector.

Use a multimeter set to measure DC Voltages. Set the multimeter to the 20V dc maximum range. Connect the multimeter's red (+) probe to one of the orange wires and its black probe (ground) to one of the black wire metal contacts in the connector body or the metal RF shield.  

Is 5Vdc present?

[Cytra]

11 minutes ago, KaosEngineer said:

Make sure that the power supply unit's 5Vdc standby voltage is present at the motherboard's power connector.

Use a multimeter set to measure DC Voltages. Set the multimeter to the 20V dc maximum range. Connect the multimeter's red (+) probe to one of the orange wires and its black probe (ground) to one of the black wire metal contacts in the connector body or the metal RF shield.  

Is 5Vdc present?

Yes, 5Vdc is present.

[Cytra]

Here’s a pic of the inside:

https://postimg.cc/zV692884

[KaosEngineer]

2 hours ago, Cytra said:

Yes, 5Vdc is present.

Okay, now measure the voltage level present at pin 4 of the LPC debug port.  

See: LPC Debug Port - xboxdevwiki for the pinout.

Press the power button. Does the reading go to 0 Vdc?  Next, release the power button. What value does it return to?

 

[Cytra]

20 minutes ago, KaosEngineer said:

Okay, now measure the voltage level present at pin 4 of the LPC debug port.  

See: LPC Debug Port - xboxdevwiki for the pinout.

Press the power button. Does the reading go to 0 Vdc?  Next, release the power button. What value does it return to?

 

Do I have to put the prong not being used somewhere else? I tried both prongs in port 4 individually and both came up as 0.

[Prehistoricman]

48 minutes ago, Cytra said:

Do I have to put the prong not being used somewhere else? I tried both prongs in port 4 individually and both came up as 0.

Prong = multimeter probe? If yes then usually you put black to ground (the xbox shield) and red to the thing you want to measure.

[Cytra]

Yes that's what I meant haha, my apologies. I re-did it (I made sure to make the black probe grounded this time) and the reading is still 0.

[Prehistoricman]

Sounds like the power button is shorted to ground without the button being pressed in. Usually the power button shorts this signal to ground. Can you unplug the front panel (yellow wires) and re-measure?

[Cytraz]

5 minutes ago, Prehistoricman said:

Sounds like the power button is shorted to ground without the button being pressed in. Usually the power button shorts this signal to ground. Can you unplug the front panel (yellow wires) and re-measure?

Responding from alt account. I unplugged the yellow wires and the reading in port 4 is still 0.

[KaosEngineer]

52 minutes ago, Cytraz said:

Responding from alt account. I unplugged the yellow wires and the reading in port 4 is still 0.

AC power is connected and you still read 5Vdc on the orange wires of the power supply connector?

Edit: You mean pin 4 of the LPC Debug port header location.

The second hole up on the left of the port looking from the front of the console.

[Cytraz]

26 minutes ago, KaosEngineer said:

AC power is connected and you still read 5Vdc on the orange wires of the power supply connector?

Edit: You mean pin 4 of the LPC Debug port header location.

The second hole up on the left of the port looking from the front of the console.

Yes to both.

[Prehistoricman]

Next to the front panel connector on the motherboard you will see a bunch of resistors.

Can you measure the voltage on the left and right side of those two resistors R3G6 and R3G4? These form a potential divider to drop the voltage to 3.3V for the Xyclops.

[Cytraz]

19 minutes ago, Prehistoricman said:

Next to the front panel connector on the motherboard you will see a bunch of resistors.

Can you measure the voltage on the left and right side of those two resistors R3G6 and R3G4? These form a potential divider to drop the voltage to 3.3V for the Xyclops.

Both measure at 0, even when the on button is pressed.

[Prehistoricman]

2 minutes ago, Cytraz said:

Both measure at 0, even when the on button is pressed.

Both? There are 4 measurements: each side of the two resistors.

[Cytraz]

4 minutes ago, Prehistoricman said:

Both? There are 4 measurements: each side of the two resistors.

Sorry I meant all 4.

[Prehistoricman]

Super weird! That must mean that somehow the 5V standby supply isn't reaching most of the motherboard. Can you check these 3 points:

The two arrows on the right refer to the inductor's two ends that go into the motherboard.

[Cytra]

@KaosEngineergot any other suggestions? I've been pming with PrehistoricMan and we've tried a few different things. What are your thoughts?

[KaosEngineer]

2 hours ago, Cytra said:

@KaosEngineergot any other suggestions? I've been pming with PrehistoricMan and we've tried a few different things. What are your thoughts?

Is the collector - the pin on the side by itself - of the PNP SMD transistor at location Q7C2 at 3.3Vdc?

[Cytra]

On 7/16/2022 at 10:10 PM, KaosEngineer said:

Is the collector - the pin on the side by itself - of the PNP SMD transistor at location Q7C2 at 3.3Vdc?

There's no reading on either side... I wonder if the motherboard is even receiving any power at all?

[SS_Dave]

On 7/19/2022 at 12:04 PM, Cytra said:

There's no reading on either side... I wonder if the motherboard is even receiving any power at all?

My experience with a version 1.6 supply is unless it gets a POW OK ( blue wire) from the mother board within a second or two it shuts down completely ( no 5 volt stand by)

What happens if you have your meters black probe on ground ( Black wires in the IDE plug or 20 pin plug  or on the metal shield ) and the red probe in the 5 volt ( orange wires 20 pin plug) and the same but have the red probe in blue wire in the 20 pin plug then connect the AC in lead after it's been un-plugged from the mains for 60 seconds.

Depending on the multi-meter you should see a a 3 volt on the blue and 5 volt on the orange wires, if you have a slow meter it may not fully reach the reading quick enough but let me know what happens.

 

Cheers

SS Dave

Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

[cch2001.tw]

On 7/15/2022 at 2:27 AM, KaosEngineer said:

Make sure that the power supply unit's 5Vdc standby voltage is present at the motherboard's power connector.

Use a multimeter set to measure DC Voltages. Set the multimeter to the 20V dc maximum range. Connect the multimeter's red (+) probe to one of the orange wires and its black probe (ground) to one of the black wire metal contacts in the connector body or the metal RF shield.  

Is 5Vdc present?

Hello, Kaos, I encounter same problem. Mine is 1.6 softmod and everything is great before today. Because I saw clock cap had bulge, so I bought one and try to replacement. Initial clock cap is 1.0F/2.5v, I changed 1.0F/2.7v. After replacement, the tragedy begins.... My xbox can not turn on power and I only do this work, no take off PSU

Finally, I change back bulge clock cap, result is same, can not power on. Also check other caps, they are normal. (no bulge)

So....I tried to search more solution to fixed and I found this thread, follow previous power check, mine is only 4Vdc. Could you help me how to do next step? thanks a lot!!!!

[Bowlsnapper]

On 7/22/2022 at 5:58 PM, SS_Dave said:

My experience with a version 1.6 supply is unless it gets a POW OK ( blue wire) from the mother board within a second or two it shuts down completely ( no 5 volt stand by)

What happens if you have your meters black probe on ground ( Black wires in the IDE plug or 20 pin plug  or on the metal shield ) and the red probe in the 5 volt ( orange wires 20 pin plug) and the same but have the red probe in blue wire in the 20 pin plug then connect the AC in lead after it's been un-plugged from the mains for 60 seconds.

Depending on the multi-meter you should see a a 3 volt on the blue and 5 volt on the orange wires, if you have a slow meter it may not fully reach the reading quick enough but let me know what happens.

 

Cheers

SS Dave

Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

After reading this whole thread, I was going to say that the probability of your meter never giving a positive reading to anything is becoming more and more improbable... and suspicious. Lol. You sure the multimeter is working?

[cch2001.tw]

9 hours ago, Bowlsnapper said:

After reading this whole thread, I was going to say that the probability of your meter never giving a positive reading to anything is becoming more and more improbable... and suspicious. Lol. You sure the multimeter is working?

Hello Bowlsnapper, my console looks same problem as Cytra's. But I only change clock cap, no any changed for PSU and before replace clock cap is good. Any advice? thanks 

[Marty]

10 hours ago, cch2001.tw said:

 and everything is great before today.

Everything was working fine, then you opened it up and "worked on it"....

I suspect something regarding your work or the way you handled the motherboard points towards it's apparent death.

Scratched or broken trace, component knocked off the board, static shock, bridged points....it's hard to say.