Samsung BA41- 02206A No power

[Jmine]

Hello,

I have checked the board for shorts, but no shorts, 19V rail is present. I measure the Charging ic (BQ735) and here are the measurements,

VCC-19.3V
ACDET- 2.7V max
ACOK- 1.6V
ACDRV- 24.6V

The 3V/5V IC (1225B)doesn't output 3.3V.

I couldn't find schematics for the board.

will this work if I just replace the 3V/5V IC?

[Sephir0th]

Re: Samsung BA41- 02206A No power

Usually not. You have to troubleshoot the circuit instead. You even haven't mentioned for which of the various +3V rails you're looking. So please clarify.

[Jmine]

Re: Samsung BA41- 02206A No power

Usually not. You have to troubleshoot the circuit instead. You even haven't mentioned for which of the various +3V rails you're looking. So please clarify.

The 1225B ic doesn't have any voltage on it's pins. Even vin is absent.

[mcplslg123]

Re: Samsung BA41- 02206A No power

Are you sure about the ACOK measurement?? ACDRV seems fine ,so 19V should reach CLR if there is no shorting on +19V rail. Are you getting 19V on CLR?? If 19V reaches CLR, then you should have VIN at 1225B controller.

[Jmine]

Re: Samsung BA41- 02206A No power

Are you sure about the ACOK measurement?? ACDRV seems fine ,so 19V should reach CLR if there is no shorting on +19V rail. Are you getting 19V on CLR?? If 19V reaches CLR, then you should have VIN at 1225B controller.

Acok is variable. Now it's around 1.2v. yes 19v is present at the CLR. I've notice that there is 19.04v at the charge ic vcc and elsewhere in the board it is 19.6v

Please bear with me I'm a complete noob who is willing to learn stuff.

[mon2]

Re: Samsung BA41- 02206A No power

As mentioned, ACOK is too low of a voltage.

There will be a pull up resistor on the ACOK pin to either the REGN pin of this charger IC or to the voltage output from the referenced 1225B ic.

Locate this pull up resistor. Then check the voltage to ground on each side of this resistor.

Next, locate the 3v3 rail output on the 1225b IC. Does this power rail also show the same low 1v2 value?

If the power rails are low in reading, remove all power and check if they are being loaded down due to a short by checking their resistance to ground.

Do confirm that REGN is stable at ~6 volts.

Once you locate the pull-up resistor on ACOK, post clear pics of this area of the logic board.

[Jmine]

Re: Samsung BA41- 02206A No power

As mentioned, ACOK is too low of a voltage.

There will be a pull up resistor on the ACOK pin to either the REGN pin of this charger IC or to the voltage output from the referenced 1225B ic.

Locate this pull up resistor. Then check the voltage to ground on each side of this resistor.

.

there is something wrong with the ACOK reading, it keeps varying, now on the resistor

Closer to ACOK: 0.676V
Other side: 0.04V to almost zero v

Next, locate the 3v3 rail output on the 1225b IC. Does this power rail also show the same low 1v2 value?

.

Yes, It Shows the Crazy values just as ACOK

If the power rails are low in reading, remove all power and check if they are being loaded down due to a short by checking their resistance to ground.

Do confirm that REGN is stable at ~6 volts.

board.

REGN is stable at 6V

3.3 LDO (pin 3): Not shorted to ground
Vin(pin 12) : 3 0hms
5V LDO (pin 13): 2 0hms

Does this mean the 1225B Is shorted? that's why I don't have 19V on VIN, Or could it be shorted caps?

See the attached.

[mon2]

Re: Samsung BA41- 02206A No power

The LDO rails will only work if VIN is present.

VIN will follow the 2 * DCin mosfets.

The ACOK pull up needs the LDO rails.

Review the DCin mosfets and measure each pin to ground voltage.

Since gate voltage is ok, each DCin mosfet should be enabled. Confirm it. At least one is defective.

[Jmine]

Re: Samsung BA41- 02206A No power

The LDO rails will only work if VIN is present.

VIN will follow the 2 * DCin mosfets.

The ACOK pull up needs the LDO rails.

Review the DCin mosfets and measure each pin to ground voltage.

Since gate voltage is ok, each DCin mosfet should be enabled. Confirm it. At least one is defective.

I have 19v on the CLR. I observed 19V at the resistor on the VIN of the 1225B.
The VIN resistor which is supposed to be 3.3 ohms is at 1.5k ohms. (I was able to find a schematic).
There is only 20mv after the resistor.

[mcplslg123]

Re: Samsung BA41- 02206A No power

Replace the defective resistor with rated value on VIN of 1225B but the cause of concern is low value on 5V LDO. You need to remove the 1225B ic and then re-measure resistance on 5V LDO. If it goes significantly up in K ohms range, then IC is bad.However, if the resistance remains more or less same , then you have some shorted component on 5V rail. Then can be found by injecting 1V on 5V LDo rail.

PS: I dont think anything is wrong in the dc-in fets as ACDRV is fine and 19V rail is reaching CLR.

[Jmine]

Re: Samsung BA41- 02206A No power

Replace the defective resistor with rated value on VIN of 1225B but the cause of concern is low value on 5V LDO. You need to remove the 1225B ic and then re-measure resistance on 5V LDO. If it goes significantly up in K ohms range, then IC is bad.However, if the resistance remains more or less same , then you have some shorted component on 5V rail. Then can be found by injecting 1V on 5V LDo rail.

PS: I dont think anything is wrong in the dc-in fets as ACDRV is fine and 19V rail is reaching CLR.

I replaced the resistor and after removing the 1225B ic the 5VLDO shows 60 Ohms to the ground.

I injected 5v to the 5V LDO and the RAM ic is getting hot.

After placing the same 1225B, I think 19v is shorted to the ground and the 1225B is getting hot.

I guess both chips are bad and have to replace them.

Any thoughts?

[mon2]

Re: Samsung BA41- 02206A No power

For injection, NEVER inject more than 1 volt unless it is 100% clear that there is no CPU high side mosfet short on the board.

The rule of thumb is to use the lowest power rail as a max voltage for injection.

Something on the 1225B is wrong if it is heating up. Was it soldered properly?

Flux and reflow the part and 'make it dance' (Louis' videos) with a gentle push of the tweezers when the solder paste is in liquid mode. This gentle push will then reset the solder balls under the IC to align, 'like soldiers'.

[Jmine]

Re: Samsung BA41- 02206A No power

A Great analogy!


I removed the chip and 5 pins of it are shorted to the ground. I will replace both the ICs and report back.