SONY MBX 226 19V no post

[Yosua]

hello all my colleagues, I want to ask for help to solve this mobo soni mbx 226, the case is 19v just stuck on the drain ac fet and it doesn't want to spread, I've tried to replace the acfet but the case is the same, and I've also replaced the charger ic it's still the same , after I measured the ACDET pin on the charger ic bq24753a it only outputs 1.04v voltage, and I've measured the resistance on the 2 pulldown resistors on the acdet line and they are normal


can anyone give me advice?

[mon2]

Re: SONY MBX 226 19V no post

Measure the voltage at the fuse, both sides of the dc adapter.

Also the voltage of DC_IN @ PR28, pin #1.

Post each measurement. Use 20v or higher DC mode scale.

[Yosua]

Re: SONY MBX 226 19V no post

Measure the voltage at the fuse, both sides of the dc adapter.

Also the voltage of DC_IN @ PR28, pin #1.

Post each measurement. Use 20v or higher DC mode scale.

thank you for your little time sir, and for both sides of the fuse have the same voltage 19v

this is for PR28 . measurement

pin1 : 19v
pin2 : 1.04v

[Yosua]

Re: SONY MBX 226 19V no post

I forgot to say that on my multitester the 19v voltage that appears is (-), even though my probe is not reversed.

[mon2]

Re: SONY MBX 226 19V no post

19v voltage that appears is (-), even though my probe is not reversed.

This is not correct if indeed you are with RED meter probe on the 19v DC adapter pin; black to ground.

Is the DC adapter the original ? Or is it a universal adapter where the tip can be rotated ?

From the description, the adapter may have the tip reversed.

Remove it and check the DC adapter directly to see if the polarity is correct or not.

A proper adapter should show +19v at the fuse and also at the pin #1 of the ACDET voltage divider resistor pair. Then if the resistors are of the proper value, the voltage at the common junction = ACDET should be > 2v4 and this informs the charger IC that the adapter is worthy of powering this logic board.

[Yosua]

Re: SONY MBX 226 19V no post

This is not correct if indeed you are with RED meter probe on the 19v DC adapter pin; black to ground.

Is the DC adapter the original ? Or is it a universal adapter where the tip can be rotated ?

From the description, the adapter may have the tip reversed.

Remove it and check the DC adapter directly to see if the polarity is correct or not.

A proper adapter should show +19v at the fuse and also at the pin #1 of the ACDET voltage divider resistor pair. Then if the resistors are of the proper value, the voltage at the common junction = ACDET should be > 2v4 and this informs the charger IC that the adapter is worthy of powering this logic board.

I only use a universal dc power supply, sir, later I will try with the original charger, while for the PR28 yesterday I measured the resistance:

430k : regardless of board

251k : mounted on the board

[mon2]

Re: SONY MBX 226 19V no post

1) I think the polarity of your universal power supply is reversed. Confirm it before proceeding and better to use the original power supply.

2) After the above -> check ACDET again. It should be a better reading and > 2v4.

3) If ACDET is not correct, remove all power and check these 2 resistors again. Carefully remove off the board with flux and check their values while out of circuit. The resistance is critical to dial up the proper trigger voltage for the ACDET signal. If the final voltage of ACDET is under 2v4, the charger will disable the first DCIN mosfets.

[Yosua]

Re: SONY MBX 226 19V no post

1) I think the polarity of your universal power supply is reversed. Confirm it before proceeding and better to use the original power supply.

2) After the above -> check ACDET again. It should be a better reading and > 2v4.

3) If ACDET is not correct, remove all power and check these 2 resistors again. Carefully remove off the board with flux and check their values while out of circuit. The resistance is critical to dial up the proper trigger voltage for the ACDET signal. If the final voltage of ACDET is under 2v4, the charger will disable the first DCIN mosfets.

ok sir, later i will try to use the original dc adapter, then i want to ask,

does it mean the board is in trouble, when the resistor is detached from the board the value is normal, but when the resistor is attached its value drops

[mcplslg123]

Re: SONY MBX 226 19V no post

I forgot to say that on my multitester the 19v voltage that appears is (-), even though my probe is not reversed.

Perhaps 'coz your dc supply voltage is set at higher then 19V and multimeter is not able to read it. Change your multimeter to 200V and perhaps it will show correct reading.

[Yosua]

Re: SONY MBX 226 19V no post

1) I think the polarity of your universal power supply is reversed. Confirm it before proceeding and better to use the original power supply.

2) After the above -> check ACDET again. It should be a better reading and > 2v4.

3) If ACDET is not correct, remove all power and check these 2 resistors again. Carefully remove off the board with flux and check their values while out of circuit. The resistance is critical to dial up the proper trigger voltage for the ACDET signal. If the final voltage of ACDET is under 2v4, the charger will disable the first DCIN mosfets.

sorry I just got back to this message, the result is still the same even though I use the original adapter sir and it's still -19v

[Yosua]

Re: SONY MBX 226 19V no post

Perhaps 'coz your dc supply voltage is set at higher then 19V and multimeter is not able to read it. Change your multimeter to 200V and perhaps it will show correct reading.

I use 200v mode the result is still the same sir

[mon2]

Re: SONY MBX 226 19V no post

Can you post a picture of your meter to show how you are taking this measurement ?

Red meter lead on the point to test; Black meter lead to ground (shield is ok) on the logic board.

You should not have -19v as a reading.

[Yosua]

Re: SONY MBX 226 19V no post

Can you post a picture of your meter to show how you are taking this measurement ?

Red meter lead on the point to test; Black meter lead to ground (shield is ok) on the logic board.

You should not have -19v as a reading.

you are right sir, it turns out that there is a problem with the dc cable, now the voltage is + 19v, but the problem is not over, 19v stops on the second fet, and the gate on the 19v fet

[Yosua]

Re: SONY MBX 226 19V no post

Can you post a picture of your meter to show how you are taking this measurement ?

Red meter lead on the point to test; Black meter lead to ground (shield is ok) on the logic board.

You should not have -19v as a reading.

and I also made a mistake, I forgot to remove the adapter when I replaced the bq24753 ic