Sony DA0HK5MB6F0 MBX-269 problem

[kahlenberg]

Hi,

I have a DA0HK5MB6F0 MBX-269 motherboard and it is not working. I have schematics and I checked all power supplies and found out that 1.05V 15A PS controlled by PU105 was not working. I checked MOSFETS PQ252 & PQ253 and PQ253 was damaged. I replaced it but still PU105 is not producing 1.05V.
When I press power button, 3 LEDS LED_NUM1, LED_CAP1, LED_SCR1 are lighting and orange LED D13 (SATA_ACT) is lightning for 2-3 seconds. Then it powers down again.
On screen there is nothing.

What is the problem? I don't have any EEPROM programmer.
If I replace KU1 NPCE885L, can it work?
If yes, where can I find it?

Thanks.

[emestee]

The power down is probably the result of protection kicking in. This suggests that the KBC code is executing.

First figure out what's wrong with the 1.05 rail. Check its output resistance, the enable signals, gate drive oscillation, TONSEL signals etc.

[kahlenberg]

Originally Posted by emestee

The power down is probably the result of protection kicking in. This suggests that the KBC code is executing.

First figure out what's wrong with the 1.05 rail. Check its output resistance, the enable signals, gate drive oscillation, TONSEL signals etc.

Thanks for answer.
There is only one enable signal at PU105, pin 15. When I press power button enable signal is 3V. TON signal (pin 16) is 1V. Power supply for IC is 5V at pin 2.
Output resistance is around 12 ohm. I measured it at PC493.
Can I measure gate frequencies with multimeter? Is it DC and square wave?

[kahlenberg]

Ok, I was able to measure (or not measure) gate frequencies. My multimeter has also frequency measurement mode. When I measure other MOSFETs' gate, I can read some frequencies.
When I measure gates of PQ252 & PQ253, there is no signal.
So, that means PU105 is damaged?
Where can I find it?

[emestee]

Urgh, I had to write this comment three times because the comment is glitching.

The presence of TONSEL, both VDD inputs and the enable signal will make the chip attempt to start driving the gates. The problem is you can't really verify this without an oscilloscope. The protections will kick in really quick and the multimeter sampling wont be fast enough to catch it.

You can replace the chip, but I'd suggest prior to that replace the high side mosfet just to be sure, and also test the components in the feedback circuits. I'm also curious if PR498 and PR499 are present on the board.

[kahlenberg]

High-side MOSFET seems to be ok. All componnets in the feedback circuits seem also to be ok. I can not find PR498 and PR499 in vicinity of PU105.
I downloaded also .brd file but I can not open it in Eagle v9 or v6.
I am getting "Error: line 1, column 1: Start tag expected."

So, I really can not find the resistors

Edit:
Hmm, it seems that PC496 is not present. I don't know, maybe I removed it with hot-gun while replacing PQ253.
What is this TONSEL signal? PC496 and PR374 build a RC oscillator?

[stingerchamp]

.brd file open in openboardview.org

[emestee]

TONSEL sets the frequency at which the IC will drive the gate, basically.

The resistor is to set the frequency, the capacitor is to dampen the fluctuations of the VIN line. The oscillator is internal to the chip. Without the cap the circuit will probably work but will lose some stability.

[kahlenberg]

Thanks for suggesting openboardview.org
Board looks like a little bit different but I could find PR498 and PR499. They both are on the board.

[stingerchamp]

Glad it worked 😊

[udai]

sir i have problem with da0hk5mb6f0 ... with low power button voltge .. showing only .5v.,
3v 5v ok , ac ok, dsw 3.3 v ok, rtc ok, still same even changed io , what makes 3.3 in power button . their is no pull up down ressistor found in it
pl help