Observation
A photo of the debug LED or POST code during startup.
New PC Won't POST
Use this flow when a brand-new build powers on but never reaches a usable POST or BIOS state. Keep the next check focused on debug signals, one-stick RAM testing, BIOS support, and minimum boot before swap testing.
Safety first: do not interrupt a BIOS update, and stop for burning smell, liquid damage, or visible socket or power damage.
What this flow is for
This flow is for first-boot systems that spin up but still never reach POST, BIOS, or a usable display, so you need to separate RAM, BIOS, CPU support, and minimum-boot issues cleanly.
First safe checks
- Read the board debug LED, POST code, or beep pattern first.
- Clear CMOS and test with one RAM stick in the recommended slot.
- Remove non-essential storage, USB devices, and add-in cards.
- Confirm the CPU is supported by the board's BIOS version.
- Move to a minimum-boot breadboard test if the board still will not POST.
Evidence requests
Ask for the smallest missing proof
Photo or screen
The exact CPU, motherboard, and RAM models.
Change log
A note showing whether one-stick minimum boot changes the behavior.
Likely causes
Most likely problem buckets
Memory setup issue
RAM seating, slot choice, or training is the most common first-build blocker.
BIOS compatibility issue
The CPU may need a newer BIOS before the board will POST cleanly.
Minimum-boot setup problem
CPU power, cooler pressure, or extra devices can keep the board from completing POST.
Component fault
If minimum boot still fails, RAM, board, or CPU swap testing becomes more likely.
Next safe steps
Take one step at a time
ACT-PC-008
Read the debug LED or POST code and strip the system to minimum boot.
ACT-PC-009
Clear CMOS and test one RAM stick in the board's recommended slot.
ACT-PC-004
Breadboard the system outside the case to rule out shorts and extra variables.
ACT-PC-016
Confirm CPU support and use only a vendor-approved BIOS update path if it is required.
Best follow-up ask
Which debug LED or POST code do you see, and are you testing with one RAM stick in minimum boot?
When to stop and hand off
Minimum boot, CMOS clear, and BIOS compatibility checks still do not produce POST.
Support links
Stay with the smallest boot problem that fits
If the system starts reaching display output, Windows recovery, or obvious crash behavior, move into the closest guide instead of staying on the no-POST path.
Open PC repair roadmap Describe an issue