I have an ASUS ROG gaming laptop purchased around 2021 with its original 240 W power adapter. The adapter is rated for 100–240 V AC input at 50–60 Hz and provides 20 V DC at 12 A. Recently, it only seems able to supply enough power after it has been running for a while. If it has been idle for roughly 15 minutes, charging becomes unstable and may eventually stop. I can sometimes get it working by drawing power gradually, then slowly increasing the load until the laptop can run at full power. It behaves almost like something needs to warm up first. What component or failure mode could cause this? My initial guess is thermal expansion or a temperature-sensitive connection, but I'd like to understand the likely cause.
3 Answers
Make sure the problem is really inside the brick by checking the DC plug, cable, and laptop charging socket for looseness, damage, or excessive heat. A broken conductor near the plug can also produce intermittent charging, although the warm-up pattern points more toward the adapter’s internal electronics. Use a replacement with the same voltage, the correct connector and polarity, and at least the original 240 W rating. A random USB-C GaN charger may not provide enough power for a gaming laptop unless the laptop specifically supports the required USB-C charging standard and wattage.
That behavior strongly suggests a failing power adapter rather than something the laptop is supposed to do. Possible causes include aging electrolytic capacitors whose electrical characteristics improve as they warm up, a cracked solder joint, or a deteriorating component that is sensitive to temperature. The gradual-load trick may simply be keeping the adapter inside a range where its protection circuitry does not shut down. A 240 W adapter is working with high currents, so continued use could lead to more severe failure or overheating. Replacing it with a compatible, properly rated adapter is the safest approach.
Thermal expansion is possible, especially with a cracked solder joint or a component connection that changes resistance as it warms. However, the most common explanation for an older switching power supply that starts badly and improves after warming is degraded capacitors. They can have increased equivalent series resistance when cold, causing excessive ripple or unstable regulation. The adapter’s control circuit may then enter and leave protection mode until the parts warm up. Don’t open the brick unless you know how to safely discharge high-voltage capacitors; even unplugged adapters can retain a dangerous charge.
That makes sense. I was mainly trying to understand what might be failing, but I agree that replacing the adapter is probably the sensible option.