Lenovo Yoga 500-15ISK several faults

[s_henya]

Hi guys,

Anyone ever worked on this board before?
Few issues im trying to resolve:

1. Laptop will not power up without main battery connected (missing 3.3v line)- measuring on the 3.3v coil i can see 0v but for split second it jumps to 3.3v and drops again.
Is this laptop supposed to power on only with battery connected?

2. Battery voltage + line is getting 19v, for my experience 7.4v battery isn't meant to be charged with main line voltage- is this normal?

3. No display on laptop screen, if i disconnect the LVDC cable and connects by HDMI everything works- possible LVDS cable\ mainboard issue\ screen connection issue.

Any tips?

[mon2]

Is this laptop supposed to power on only with battery connected?

Every laptop should be able to power only using only the battery, provided that the battery is charged. Do review the battery charger sticky above by piernov. It is very possible that you have a leaky mosfet in the power path from the external power adapter and the main power rail (V20B+).

Review the details below on how to test the mosfets. Do inspect and measure the mosfets that are @ PQ311 and PQ312. At least one of these may be leaky.

2. Battery voltage + line is getting 19v, for my experience 7.4v battery isn't meant to be charged with main line voltage- is this normal?

Correct. Way too high of a voltage to charge the battery pack. May have caused damage to the battery pack. This is implying that the high side and/or low side battery charging mosfets are not working correctly to dial down the ~19 volts that is from the power adapter. These 2 mosfets must turn on / off together to lower the ~19 volts to a safer charge voltage.

Remove all power. Meter in resistance mode. Measure the resistance across these mosfets to check if they are leaking.

Measure:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement in ohms. A low resistance means the mosfets is probably leaky and should be replaced. Check the high side and also the low side mosfet.

[s_henya]

Dear Mon,

Thank you for always finding time to comment and suggest solutions!
in this case i think i was misunderstood.

The battery is charged, laptop is able to power on and work using only battery- normal so far.
If i disconnect the battery and power on using only power from the charger the laptop does not power on.
Measuring on the 3.3v coil i can see 0v but for split second it jumps to 3.3v and drops again.
Is this laptop supposed to power on only with battery connected (charger alone isn't enough)?


Battery charging FETs tested good (OL between Gate to source. Gate to Drain. Source to Gate Source to Drain. Drain to Source and Drain to Gate)
not sure how to continue....

maybe schematics or boardview?

[mon2]

I think we are still on the same page.

OL between...

Switch to a higher scale on your meter until you have a resistance measurement. OL ('over limit') often means the meter scale is too low for the measurement. The schematics are locked to my paid subscription and so far, unable to crack the lock mechanism. Will check on the bv files and their state.

[s_henya]

For mosfet resistance test i usually use diode mode for voltage drop, think it would be more useful.
will check and reply back.

[mcplslg123]

I confirm that this board works only in adapter also. However, seen a couple of boards where laptop dont powers on without a battery(Dell).
For mosfet checking ,better way is resistance mode with meter set to 200K or higher scale.