Fixing Unbootable 15-Series HP Notebooks with Caps Lock Steady Blink

Yesterday I participated in the repair of an HP 15-R110dx notebook computer that refused to boot or do anything at all. When powered on, its Caps Lock key light blinked once every three or four seconds; the pattern wasn't described in any HP documentation that I could find.

It turns out that the CMOS state was corrupt or unusable in some way, so the CMOS battery needed a disconnect/reconnect cycle. Actually performing the repair was exceptionally difficult because the RAM and CMOS battery are under a host of important and inconvenient-to-remove parts, and not accessible from the bottom.

The general procedure to fix this problem is:

1. Remove the main battery and disconnect the power cable
2. Remove RAM and CMOS battery
3. Press the power button (discharges any extra energy)
4. Reinsert RAM and CMOS battery
5. Connect power cable and/or main battery
6. Reboot when prompted about CMOS corruption

Step 2 is written here as five simple words, but it is a challenge, as is reassembly. Disassembly goes like this:

1. Remove all screws from bottom panel
2. Remove the DVD drive
3. Remove the screws hidden under the DVD drive slot
4. Remove the screws hidden under the back two rubber feet
5. Pry the keyboard out and disconnect its cable
6. Pry the larger surrounding plastic piece off
• Be careful to remove the keyboard separately or you risk tearing the power button cable. (Guess who did that. Twice.)
7. Unscrew the metal plate and remove it
8. Unscrew the motherboard and tip it up toward the screen
• Screws for the motherboard are marked with white arrows.
9. Remove the RAM and CMOS battery on the underside of the motherboard.
• Yes, the RAM is on the underside of the motherboard, under all that other stuff. That is just appalling.

If you damaged the power cable in substep 6, you'll need to short across it when applying power for step 3. Fortunately, it's possible to solder it back together.

RubberWilbur's video guide to RAM replacement for these models was very helpful for the disassembly operation. For putting it back together, assembly is the reverse of disassembly.

Once everything is back together and powered, BIOS should come up with a message about CMOS corruption and a directive to press Enter. Press Enter (or just reboot) - CMOS will be reset and all will be good.