71R-H14BW6-T830, clock stops when shutdown

[Fontana]

Hi!
Funny problem. I have a board, model 71r-h14bw6-t830, it's a shuttle board used commonly on a lot of cheap laptops/AIOs.
The clock (RTC) is not working when the machine is turned off. Doesn't matter if it is connected to dc power or not. When the PC is powered on, the clock works fine.
I tried replacing Y6 and Y7 (picture below), but it doesn't seem to be an oscillator problem.
I don't have the exact schematic for this board, but I'll provide one that is similar (a variation of the same board).

Any suggestions?

OBS: when the pc is off, the clock STOPS, it doesn't reset. When turned on again, it starts counting time normally (with the clock now starting from where it was when it was turned off). I thought of just setting up a script to resync time on logon but I rather use that as a last resort.

[mon2]

Re: 71R-H14BW6-T830, clock stops when shutdown

Check the voltage at D11, pin #3 (+3.3VA_RTC).

What is the voltage when powered ON?

What is the voltage when powered OFF?

This is a dual common cathode diode that will select the higher of the 2 input voltages.

When the power supply is OFF, the RTC should be powered from the diode leg #1 connected to the battery.

[Fontana]

Re: 71R-H14BW6-T830, clock stops when shutdown

Check the voltage at D11, pin #3 (+3.3VA_RTC).

What is the voltage when powered ON?

DC plugged, machine turned off, 2.87V (3.08V on pin2)

What is the voltage when powered OFF?

DC off, 2.85V (2.98V on pin1)

Sorry, forgot to mention I had tested the diode already.
Also, SRTC_RST# after R407 is 2.8V

[mon2]

Re: 71R-H14BW6-T830, clock stops when shutdown

Is the crystal @ Y6 a known good crystal ? Should be 32.768khz which are very common for RTC circuits.

[Fontana]

Re: 71R-H14BW6-T830, clock stops when shutdown

Is the crystal @ Y6 a known good crystal ? Should be 32.768khz which are very common for RTC circuits.

I have no way to measure it, but it should be fine. I removed it from a board of the same exact same model which problem wasnt related. unless I broke it when replacing but I doubt it. I used heat from bottom of the board to remove it and soldered it back with unleaded.

[mon2]

Re: 71R-H14BW6-T830, clock stops when shutdown

What is the voltage @ RTC_TEST# ? (C463 & R406)

Remove all power -> meter in resistance mode. Check the resistance to ground on each side of the same crystal (Y6).

This clock crystal is not very critical and can be tested with the same frequency of component from other boards - even different packages.

[Fontana]

Re: 71R-H14BW6-T830, clock stops when shutdown

What is the voltage @ RTC_TEST# ? (C463 & R406)

2.8V

Remove all power -> meter in resistance mode. Check the resistance to ground on each side of the same crystal (Y6).

more than the meter can measure, but this is also the case in a known good board that I have. in diode mode .9V drop

[mon2]

Re: 71R-H14BW6-T830, clock stops when shutdown

Reflash the BIOS to the latest if you have not done so already. Just in case there is some s/w fault linked to the RTC. Otherwise, the checks you have performed look good to me.

[Fontana]

Re: 71R-H14BW6-T830, clock stops when shutdown

I have, but since I have a working board I'll try replacing the bios chip altogether. will try another crystal as well for peace of mind.
but if that doesnt fix the problem what can it be? the cpu?

[Fontana]

Re: 71R-H14BW6-T830, clock stops when shutdown

I have, but since I have a working board I'll try replacing the bios chip altogether. will try another crystal as well for peace of mind.
but if that doesnt fix the problem what can it be? the cpu?

replaced bios and ec rom chips. replaced crystal again. no luck