Printer Won't Power On After Printhead Work (No Lights, No Beep, No Screen): What F1/F2 Fuses Mean and What to Check Next

Question: I watched your videos and used the manuals I ordered. I removed the mainboard and checked both fuses (F1 and F2). They seem fine-I get a clear beep on my multimeter. I reassembled everything and tried to power on, but it's exactly the same: no sound, no beep, no display, and no light on the power button. I reattached the printhead connectors and tried holding the power button for 10 seconds, but nothing changes. The printer was powering on before I started. It even powered on after I removed the case and reseated cables. The issue started after I moved on to the printhead step. I'm pretty sure there was no liquid inside because I never put ink in the machine, and I let the printhead dry before reinstalling it. What else could cause this?

Answer: 

Based on what you tested and what you're seeing now, here's the most likely explanation and the next logical checkpoints.

1) If F1 and F2 beep good, that eliminates the most common "open fuse" failure-but not the entire power system

You did the right test. If F1 and F2 show continuity (a strong beep), they are not blown open. That typically means:

• Power is not being blocked by those primary protection fuses, or

• The failure is occurring after the fuse stage (downstream), such as:

  • a failed power-management IC (PMIC)

  • a shorted/failed regulator

  • a damaged resistor or component on a power rail

  • a corrupted firmware/logic condition that prevents boot (less common for a totally dead panel, but still possible depending on model)

So your test is useful: it narrows the issue from "simple fuse" to "deeper power/logic."

2) The most important "simple" recheck: the Start/Power button cable and the LCD/control panel cable

When a printer shows no lights and no screen, a surprisingly common cause after reassembly is a missed or partially seated cable-especially:

• Start/Power button FFC cable

• LCD/control panel FFC cable

• Any small FFC that feeds the front panel board

Even if "most" cables look correct, one FFC can be:

• slightly crooked

• not fully inserted

• inserted upside down (depending on connector type)

• not locked down with the latch

Why this matters

If the front-panel board isn't getting standby power or signal, you can get exactly what you described:

• no LED

• no screen

• no button response

• no beep/no movement

So if you're going to double-check only two cables, make it those. Your printhead work may be coincidental-front panel/control cables are often disturbed during the same stages of disassembly.

3) It's often not the printhead: surges and "downstream" power failures are common

From what you described-working before, working once during early reassembly, then completely dead after additional work-this pattern often points to something like:

• a power surge event that finally took out a weakened component

• a power rail component that failed when the system was reconnected (inrush current can do this)

• a power-management chip failing (PMIC/regulator)

• a resistor or capacitor on a power rail failing open/short

Even if there was no ink, no liquid, and the printhead was dry, electrical components can still fail without obvious external signs. Many "dead" boards show no burn marks.

4) Another possibility: firmware/logic corruption or a "latched" unstable standby state

This is less common than a hardware power failure, but it does happen: after major work (especially around printhead/carriage systems), the printer's electrical logic and mechanical positions can be out of sync. In that situation, the control circuitry can sometimes latch into an unstable standby state.

A practical power-reset method that can help in some cases is this sequence:

A clean startup sequence (to reduce latch/standby weirdness)

1. Unplug the power cord from the printer.

2. Press and hold the Start/Power button for several seconds while it is unplugged.

   • This helps discharge residual voltage from capacitors and clears some "latched" states.

3. Release the button, then plug the power cord in.

4. Press the Start/Power button once as a deliberate power-on command.

A clean shutdown approach during this troubleshooting phase

If you do get it to power on during testing, avoid storing a strange partial shutdown state:

• Instead of powering down with the Start button, unplug the power cord to remove all standby voltage and force a true zero-power state.

The idea here is: after major work, starting from a true zero-power state prevents the logic from resuming an inconsistent "half state," and it reduces the chance the control circuitry is stuck in unstable standby.

5) When F1/F2 are good and cables are correct, a professional board evaluation is usually the next step

If:

• F1 and F2 are intact

• you have confirmed the FFC cables are fully inserted and correctly oriented (especially power button and control panel)

• and the printer still shows no lights, no sound, no display

...then the most realistic next step is a board-level diagnosis. At that point, the likely culprits are:

• a failed power-management IC / regulator

• a shorted component on a power rail

• a damaged resistor network

• (less likely) firmware corruption requiring specialized tools

These are not issues that can usually be solved through normal user-level troubleshooting.

Addressing printer issues can be a complicated affair due to the hands-on nature of the problems. So, we're not able to provide remote troubleshooting, suggestions, or support for printer repairs. We offer an in-person evaluation and repair service via our local diagnostic facility, Printer Repair Service (https://bchtechnologies.com/printer-repair-service). Given the high demand, we operate on a first-come, first-served basis, so it might take a few weeks before we can get your printer scheduled to drop off. Our services are structured to repair either a whole printer or specific parts, with clear instructions on how to proceed. However, we acknowledge that our rates aren't the most economical. Thus, we highly recommend that you resort to self-help via online research. You can start by checking out YouTube or visiting our YouTube channel's homepage, BCH Technologies on YouTube (https://youtube.com/@bchtechnologies). Look for specific videos using the search icon next to "About" on the right-hand side of the menu bar. I receive dozens of queries every day asking about videos for specific topics. Having created videos over the past nine years, it's challenging to remember every single one. Therefore, using YouTube's search function would be most efficient. Plus, YouTube might suggest relevant videos from other channels that could assist you.

Thanks again for your patience and for the detailed explanation of what you tested. You did the correct first step by checking F1 and F2. If the front-panel cables are confirmed good and the printer remains completely dead, it usually means the failure is deeper on the power rail or power-management side of the board and will need professional inspection.