Hello
I was trying to fix a laptop with LA-6901P board (schematic available in many sites). It was totally dead and found a problem with the battery charging circuitry. Bypassed it and now it powers on from the ac adapter, power led stays lit, fan spins a few seconds but shows no image. It does the same powering it from a already charged battery
I started checking voltage rails and found all correct except cpu_core, which was at about 0.480v, too low for me, and vgfx_core, which remained at 0v. Removing the ram makes no difference, and removing the cpu makes vcore rise up to about 4v and board powers off itself after some seconds. Is this 0.480v vcore value normal before fully booting? What can be the problem?
If someone wants to know, problem with battery charging circuitry was a shorted low-side mosfet at the charging buck regulator and an open resistor at the charging IC (ISL6251) 5v regulator input. IC was shorted internally and I had not replacement, so I removed the charging IC, fed 5v externally to pin 1 and tied to ground the ac adapter plugged in signal (ACPRN) in order to bypass it.
Thanks to anyone reading this and willing to help.
I was trying to fix a laptop with LA-6901P board (schematic available in many sites). It was totally dead and found a problem with the battery charging circuitry. Bypassed it and now it powers on from the ac adapter, power led stays lit, fan spins a few seconds but shows no image. It does the same powering it from a already charged battery
I started checking voltage rails and found all correct except cpu_core, which was at about 0.480v, too low for me, and vgfx_core, which remained at 0v. Removing the ram makes no difference, and removing the cpu makes vcore rise up to about 4v and board powers off itself after some seconds. Is this 0.480v vcore value normal before fully booting? What can be the problem?
If someone wants to know, problem with battery charging circuitry was a shorted low-side mosfet at the charging buck regulator and an open resistor at the charging IC (ISL6251) 5v regulator input. IC was shorted internally and I had not replacement, so I removed the charging IC, fed 5v externally to pin 1 and tied to ground the ac adapter plugged in signal (ACPRN) in order to bypass it.
Thanks to anyone reading this and willing to help.
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