How to fix a Thinkpad E590/E490 that doesn't charge until the laptop turns on using battery: Difference between revisions

How to fix a Thinkpad E590/E490 that doesn't charge until the laptop turns on using battery
Device	Thinkpad E590, Thinkpad E490
Affects part(s)
Needs equipment
Difficulty	◉◉◉◌ Hard
Type	Soldering, Teardown, Part replacement

Latest revision as of 04:04, 28 January 2024

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Problem description

If your laptop charges correctly while it's on, but when reconnecting the charger while the laptop is off it refuses to charge, then this guide might apply to you.

In this case the PD controller chip (U4201: RTS5455) is probably okay, but isn't powered correctly when the laptop is off.

Symptoms

After the laptop is turned on (on battery power), it can charge successfully
Connecting the charger while the laptop is off doesn't charge it
Checking with a USB-C analyzer shows that only 5V is supplied by the charger

Solution

Diagnostic Steps

With the laptop turned off, and disconnected from the charger, check D4311 with your multimeter's diode mode. If you can't see a <1V diode drop in any of the directions, replace the diode.
- Make sure to also check downstream devices, for example the capacitor C4306. The diode may have died for a reason.
Check the output of regulator U4305 should be around 5V, if it's not:
- Check if the EN pin is high.
  - If the EN pin is low investigate Q4304 and the PD_VBUS_C_CTRL1_EC signal
- The ADJ pin, should be around 0.6V normally when there is 5V output. Since we're in the situation where there isn't 5V output, we expect there to not be 0.6V on the ADJ pin. If there is, then the regulator is operating correctly, and there's an issue with the feedback resistor divider.
- Check that the output is not shorted to ground
- Replace the U4305 regulator.

@@ Line 7: / Line 7: @@
 ==Problem description==
-Provide a concise description of the issue here. Be  as specific as possible to help readers quickly determine whether or not this is the exact problem they are facing.
+If your laptop charges correctly while it's on, but when reconnecting the charger while the laptop is off it refuses to charge, then this guide might apply to you.
-[[File:Placeholder image.jpg|thumb|Example image (Figure 1) -- No image yet. Help expand this page by uploading it!]]
+In this case the PD controller chip (U4201: RTS5455) is probably okay, but isn't powered correctly when the laptop is off.
 ==Symptoms==
-Detail all measurable or observable symptoms in this section.
+*After the laptop is turned on (on battery power), it can charge successfully
+*Connecting the charger while the laptop is off doesn't charge it
-*Symptom 1 (Figure 1)
+*Checking with a USB-C analyzer shows that only 5V is supplied by the charger
-*Symptom 2
 ==Solution==
-If the issue has a single, specific solution, provide it in this section and delete the sub-headers below. Otherwise, if there are multiple potential causes for the problem, outline the process of identifying the root cause and offer corresponding solutions below.
 ===Diagnostic Steps===
+* With the laptop turned off, and disconnected from the charger, check D4311 with your multimeter's diode mode. If you can't see a <1V diode drop in any of the directions, replace the diode.
-===Repair Steps===
+** Make sure to also check downstream devices, for example the capacitor C4306. The diode may have died for a reason.
+* Check the output of regulator U4305 should be around 5V, if it's not:
+** Check if the EN pin is high.
+*** If the EN pin is low investigate Q4304 and the PD_VBUS_C_CTRL1_EC signal
+** The ADJ pin, should be around 0.6V normally when there is 5V output. Since we're in the situation where there isn't 5V output, we expect there to not be 0.6V on the ADJ pin. If there is, then the regulator is operating correctly, and there's an issue with the feedback resistor divider.
+** Check that the output is not shorted to ground
+** Replace the U4305 regulator.