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PC Warranty Repair Singapore: Faulty CPU Caused PC Not to Boot Up
Quick answer: If your PC turns on but shows no display and the DRAM debug light is lit, RAM is not always the cause. On modern platforms, the CPU contains the memory controller, which means a faulty CPU can trigger the DRAM debug LED even when the RAM itself is working. A safe diagnostic order is: reseat RAM, test with known-good RAM, then test with a known-good CPU. In this case, the CPU was faulty, the repair was covered under Mansa's 3-year warranty, and the cost to the customer was $0 SGD.
Last updated: June 2026
Job Summary
Service
CPU diagnosis and replacement, BIOS update, stress test
Customer's Problem
PC powered on but showed no display, DRAM debug light lit on the motherboard
What We Did
Reseated RAM, tested with known-good RAM, confirmed fault with CPU swap, replaced CPU, updated BIOS, stress tested
Result
PC boots and runs stable. Repair covered under Mansa's 3-year warranty at no charge to the customer.
Watch the Repair
Can a Faulty CPU Cause the DRAM Debug Light to Turn On?
Yes. On modern AMD and Intel platforms, the CPU contains the memory controller. If the CPU has a fault, the system may fail to initialize memory during POST, which can trigger the DRAM debug light. So a DRAM light does not always mean the RAM itself is faulty.
This customer's PC powered on, but no display appeared and the DRAM debug light stayed on. They brought the PC in, and we worked through the possibilities in order: reseat the RAM, test with known-good RAM, then test the CPU. The DRAM light cleared the moment we swapped in our test CPU, confirming the customer's CPU had failed.
Root Cause
The customer's CPU had failed, preventing the system from initializing memory properly during boot. In this case, the fault appeared as a DRAM debug light because the system could not complete memory initialization. Reseating and replacing the RAM made no difference. Replacing the CPU with our test unit cleared the DRAM light and the PC booted normally, confirming the CPU as the fault.
What We Checked First
- RAM seating in both slots
- Tested with Mansa's known-good spare RAM
- Checked whether the DRAM debug light remained on after RAM testing
- Swapped CPU to Mansa's test unit
- Checked whether the PC could boot after the CPU swap
How We Fixed It
- Reseated the customer's RAM: We removed and reinstalled both RAM sticks. The DRAM debug light stayed on after reseating, ruling out a loose connection.
- Tested with known-good RAM: We replaced the customer's RAM with our verified working units and powered on. The DRAM light stayed on. This ruled out faulty RAM as the cause.
- Swapped in our test CPU: We removed the customer's CPU and installed our test CPU. On the next boot, the DRAM light was gone and the PC posted. This confirmed the customer's CPU was faulty.
- Replaced the CPU: The customer's PC was within Mansa's 3-year warranty. We replaced the faulty CPU with a new unit at no charge to the customer.
- Updated the BIOS: After the CPU replacement, we updated the motherboard BIOS before final stability testing.
- Stress tested: We ran a stress test to confirm the system was stable under load. The PC passed with no issues.
Photo Guide
Swipe or use arrows to see the repair process.
DRAM Debug Light On
The PC could turn on, but there was no display. The DRAM debug light stayed on, showing that the system could not properly detect memory during boot.
RAM Test: No Change
We reseated the customer’s RAM and tested with our spare working RAM. The DRAM light remained on, so the issue was not solved by changing memory.
CPU Swap Confirms the Fault
We tested the system with a working tester CPU. After the CPU swap, the DRAM light disappeared and the PC was able to boot properly.
BIOS Update and Stress Test
After replacing the faulty CPU with a new one, we updated the BIOS and ran a stress test to confirm the PC was stable again.
"A DRAM debug light does not always mean the RAM is faulty. In this case, the light stayed on even after testing with working RAM, but cleared once we swapped in a tester CPU. That confirmed the CPU was the real fault before we replaced it and ran the final stability test."
Mansa ComputersFinal Result
The PC boots and runs stable. No display issues, no debug lights. The stress test passed with no errors or shutdowns.
Because the PC was an existing Mansa customer build within the 3-year warranty period, the repair was covered at no cost. The faulty CPU was replaced, the BIOS was updated, and the problem was resolved.
Cost Breakdown
| Service / Parts | Cost (SGD) |
|---|---|
| Diagnosis and component testing | $0 |
| CPU replacement | $0 |
| BIOS update and stress test | $0 |
| Total (covered under Mansa 3-year warranty) | $0 |
This repair was covered under Mansa Computers' 3-year warranty for customer-built PCs. Repair costs for out-of-warranty jobs vary depending on the issue and parts needed. Press the WhatsApp button on the right to speak with us about your PC issue.
Frequently Asked Questions
Can a faulty CPU cause a PC not to boot up?
Yes. A faulty CPU is a common but often overlooked cause of no-boot issues. On modern AMD and Intel platforms, the CPU contains the memory controller, so a failing CPU can prevent POST entirely and trigger the DRAM debug light even when the RAM is fine. If reseating or replacing RAM does not clear the debug light, the CPU is the next component to test.
Why is the DRAM debug light on if my RAM is fine?
The DRAM debug light signals that the system failed to initialize memory during POST. The memory controller lives inside the CPU on modern platforms, so a faulty CPU, a damaged CPU socket, or a motherboard firmware issue can all trigger the DRAM light. Test with known-good RAM first, then test the CPU before replacing any parts.
Does Mansa Computers offer a warranty on PC builds?
Yes. Mansa Computers offers a 3-year warranty on custom PC builds. In this case, the customer paid $0 SGD because the repair was covered under warranty. Walk into our shop or WhatsApp us to check if your PC is covered.
PC Turning On But No Display?
Tell us what debug light is on and what you've already tried. We'll help you figure out the next step.
Press the WhatsApp button on the right to speak with us about your PC issue.
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