No boot after soldering RAM? Probably a cold joint.

If your device won’t boot at all, or you get beep codes that scream memory error, the most likely culprit is a bad solder joint — either a cold joint (not enough heat) or a bridge between adjacent pins.

One channel detected but not both is a dead giveaway that one of the RAM chips didn’t make proper contact. The BIOS sees the first chip because it’s connected, but the second chip might as well be on the desk.

Other signs to watch for:

• Visible gaps under the chip (reflow with more flux)
• Solder balls bridging adjacent pads (desolder braid + flux)
• Lifted pads — if you see a missing pad, you’re looking at a trace repair
• Intermittent crashes that become more frequent as the chip heats up (expanding joints lose connection)

If you get a beep code that the manufacturer lists as “memory error” (for most laptops it’s a repeating short beep), assume the soldering failed. Don’t keep rebooting — you can damage the motherboard with repeated shorts.

Next time, use more flux than you think you need.