This machine has been in a few times with an intermittent fault of not charging. Motherboard is NM-A921 (https://www.badcaps.net/filedata/fetch?id=2051581)
So back again now, not working at all. Previously the adaptor had been replaced along with the DC charge port. This is one of these trapezoid shaped orange USB ports that Lenovo were using prior to going USB-C. It has 4 pins, but the DC connector jack on the PCB has 5 pins.
Fault presentation was the adaptor is only producing 5.2V, not 20V and this isn't reaching the input of the NVDC charger (PQ5/PQ6). There are 5 pins on the connector for the DC jack on the board (JP23).
So I found not getting 5V past PQ11/PQ13. There is 1.2V on USB_ID however this fails to switch on PQ14A and pull pin 6 to ground (PQ14B does switch to ground and fed from the same logic line). If I manually ground pin 6, I get 5V passing PQ13 as expected. Don't have one, as it's a tiny 6 pin dual FET. I think this may have been the original cause of the intermittent charging if this FET was intermittently failing to switch on.
But this is where its getting confusing and I just need to confirm my logic is correct. The charger IC is a BQ24770 and I expected that grounding PQ14A I'd get the charger section to fire up, the machine to communicate to the charger via USB on pin 2/3 to negotiate 20V. But in this case, the BQ IC does not even switch on (no REGN at all). If I'm reading the datasheet right, REGN should be active at 4.6V when VCC is 5V and ACDET is above 0.6V (measured 0.7V) on this pin when fed with 5.2V. This is the correct voltage with that voltage divider of 430K/68K.
If I apply 20V from a DC power supply directly to PF2, ground pin 6 of PQ14A, the BQ charger starts working and I get fan spin. But the adaptor still doesn't switch to 20V. Do these Lenovo chargers just switch to 20V or do they require host USB comms to do that? So I'm also not getting why the BQ IC does not start at 5V, but does at 20V. REGN also present if I manually charge the battery with DC supply for a bit and get it up to 7V or so.
Doing my head in, so put it back together and order the NTZD511 FET. Don't have a boardview and the relevant area is under the pipe of the heatsink. This thing is about to go the cyber heaven.
So back again now, not working at all. Previously the adaptor had been replaced along with the DC charge port. This is one of these trapezoid shaped orange USB ports that Lenovo were using prior to going USB-C. It has 4 pins, but the DC connector jack on the PCB has 5 pins.
Fault presentation was the adaptor is only producing 5.2V, not 20V and this isn't reaching the input of the NVDC charger (PQ5/PQ6). There are 5 pins on the connector for the DC jack on the board (JP23).
So I found not getting 5V past PQ11/PQ13. There is 1.2V on USB_ID however this fails to switch on PQ14A and pull pin 6 to ground (PQ14B does switch to ground and fed from the same logic line). If I manually ground pin 6, I get 5V passing PQ13 as expected. Don't have one, as it's a tiny 6 pin dual FET. I think this may have been the original cause of the intermittent charging if this FET was intermittently failing to switch on.
But this is where its getting confusing and I just need to confirm my logic is correct. The charger IC is a BQ24770 and I expected that grounding PQ14A I'd get the charger section to fire up, the machine to communicate to the charger via USB on pin 2/3 to negotiate 20V. But in this case, the BQ IC does not even switch on (no REGN at all). If I'm reading the datasheet right, REGN should be active at 4.6V when VCC is 5V and ACDET is above 0.6V (measured 0.7V) on this pin when fed with 5.2V. This is the correct voltage with that voltage divider of 430K/68K.
If I apply 20V from a DC power supply directly to PF2, ground pin 6 of PQ14A, the BQ charger starts working and I get fan spin. But the adaptor still doesn't switch to 20V. Do these Lenovo chargers just switch to 20V or do they require host USB comms to do that? So I'm also not getting why the BQ IC does not start at 5V, but does at 20V. REGN also present if I manually charge the battery with DC supply for a bit and get it up to 7V or so.
Doing my head in, so put it back together and order the NTZD511 FET. Don't have a boardview and the relevant area is under the pipe of the heatsink. This thing is about to go the cyber heaven.
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