PU401 gets extremely hot on Motherboard la-9532p_r1.0

[Fidel Martinez]

Motherboard la-9532p_r1.0

Problem:

- Doesn't react to power button and doesn't charge battery

- The PU401 SY8208BQNC_QFN10_3X3 gets extremely hot when connecting
the power adapter.

Compal circuits show:

a SY8208DQNC_QFN10_3X3 on page 38 (PU601)

(an adjustable step-down switchmode converter with a feedback reference voltage of 0.6V)

and

a SY8208BQNC_QFN10_3X3 on page 35 (PU401)

(appears to be a fixed 3V converter)

I have replaced the PU401 IC and the problem persists and apparently the PU601 IC is also damaged.

Is it possible to use -for testing- a SY8208BQNC_QFN10_3X3 (+3VLP) as a replacement for SY8208DQNC_QFN10_3X3 (+3VALW) ???

Could you tell me how to find the cause of the PU401 regulator problem?

Greetings to All !!!

[Fidel Martinez]

Re: PU401 gets extremely hot on Motherboard la-9532p_r1.0

Could you tell me the diferece between the 2 versions mentioned the SY8208 IC?

SY8208DQNC (an adjustable step-down switchmode converter with a feedback
reference voltage of 0.6V) +3VALW
and
SY8208BQNC (a fixed 3V converter) +3VLP

[Fidel Martinez]

Re: PU401 gets extremely hot on Motherboard la-9532p_r1.0

I think PU401 will heat up if it's trying to supply too much current due to a short to ground on PU601 +3VALW (or +3VL)

[piernov]

Re: PU401 gets extremely hot on Motherboard la-9532p_r1.0

SY8208A/B/C/D not interchangeable.
Measure exact resistance to ground on +3VLP and +3VALW.

[Fidel Martinez]

Re: PU401 gets extremely hot on Motherboard la-9532p_r1.0

The PU401 SY8208BQNC_QFN10_3X3 gets extremely hot when connecting only
the power adapter without pressing the power button.

I have replaced the PU401 IC again and the problem persist.

Could you tell me how to find the cause of the PU401 regulator problem?

Greetings to All !!!

[mon2]

Re: PU401 gets extremely hot on Motherboard la-9532p_r1.0

1) are the replacement pu401 regulators known to be good parts?

2) is the part being soldered properly and with pin #1 in the right orientation?

3) the regulators are very low current at 150mA support. It should not heat up under normal conditions.

Consider to desolder the device at pu401 and measure the vin voltage. Then power down and use resistance mode to confirm the other pins on this part are not shorting. Do this check on the pcb pads without the ic soldered. Some spec is being violated.

[mcplslg123]

Re: PU401 gets extremely hot on Motherboard la-9532p_r1.0

Open jumper PJ401 and see if PU401 still becomes hot.

[Fidel Martinez]

Re: PU401 gets extremely hot on Motherboard la-9532p_r1.0

Open jumper PJ401 and see if PU401 still becomes hot.

Jumpers are used to open, close or bypass part of the electrical circuit,
what will happen if I open the PJ401?




Regards

[mon2]

Re: PU401 gets extremely hot on Motherboard la-9532p_r1.0

PJ401 is the bridge to connect PU401 output voltage rail to the rest of the logic board.

By removing this solder blob (jumper), you are isolating the +3vALW rail from the load that is downstream.

In summary, you will then be able to confirm if the voltage rail is being generated properly by PU401.

Remove the blob and

1) check if PU401 still gets hot. If it does, then PU401 circuit needs to be inspected. Has PU401 been worked on ? Maybe not soldered properly ? Damaged and needs to be replaced ?

2) if PU401 does not get hot - check the voltage on pin # 1 (PJ401). Confirm that it is +3V.

[Fidel Martinez]

Re: PU401 gets extremely hot on Motherboard la-9532p_r1.0

Open jumper PJ401 and see if PU401 still becomes hot.

what will happen if I open the PJ401?

[mcplslg123]

Re: PU401 gets extremely hot on Motherboard la-9532p_r1.0

@fidel, mon2 has already answered what you are questioning. I cant describe more and its upto you to follow suggestions or not. We as a community are just trying to help and i appreciate to cross check whether the advice is good or not as at times we can also be wrong.

[Karthik Jothi]

Re: PU401 gets extremely hot on Motherboard la-9532p_r1.0

Is this issue resolved?

[Rolandas]

Hi
I have the same problem, the PU 401 is hot, there is a short circuit somewhere. Can you help me find what's wrong?😊

[mon2]

Ragnarok??

If anything is getting (Gal Gadot) hot and bothered, double check the soldering - double check the pin # 1 orientation against the original. A part will also heat up if the component is being operated beyond the rated specs - for example, too high of a load on the downstream / consumer side of the mosfet / regulator. You can check for the excessive loading by removing all power / no battery, meter in resistance mode (not diode mode) and checking the resistance to ground on the same downstream rail(s).

Review the schematic to locate the output pins and check each resistance to ground. Post all measurements.