Printer Won't Power On Even with Correct Voltage: Possible Causes and Fixes

Question:
My printer won't turn on even though I tested the power supply and it's putting out 41 volts. I already sent the motherboard in for repair, and it tested fine. What else could be causing the problem?

Answer:

When a printer does not power on despite the power supply outputting the correct voltage, there are several potential culprits to consider:

1. Power Button and Control Panel Failure

   • The issue may be as simple as a faulty power switch or the control panel board not sending the "power-on" signal to the logic board. In some models, the power button connects via a separate cable or daughterboard, which can fail independently.

2. Loose or Damaged Power Connections

   • Even if your power supply is outputting 41 volts, a loose connector, oxidized contact, or broken cable between the PSU and the mainboard can interrupt the current. Inspect all wiring harnesses and connectors carefully for heat discoloration, pin misalignment, or breaks.

3. Secondary Power Rails on the Mainboard

   • Although your motherboard tested OK when it was sent in, keep in mind that the PSU's 41 volts typically gets converted down to multiple secondary voltages (like 24V, 12V, and 5V) that power different circuits. If one of these regulator circuits fails under load, the printer may not boot up despite the main voltage reading normal.

4. Short Circuit in Peripheral Components

   • Components like the carriage motor, stepper motor, or heater circuits can sometimes short out and prevent the printer from powering on. A shorted motor coil or a failing heater fuse may trip the PSU's protection, making it appear as if the board is dead when in fact it's being held down by a peripheral fault.

5. Capacitor or Fuse Damage

   • Check the internal fuses on both the power supply and motherboard. These are often overlooked but can silently blow during a surge. Similarly, electrolytic capacitors may still allow a voltage reading but fail under load, causing intermittent or no startup.

6. Other Rare Causes

   • In rare cases, the problem could be due to corrupted firmware preventing initialization, or an EEPROM failure that prevents the board from completing its startup sequence. While not common, it's something to consider if all electrical components test fine.

At this stage, the best approach is to perform a step-by-step isolation test-disconnect all non-essential components (motors, carriage, panel, etc.) from the motherboard and power up the board alone. If the board powers up, reconnect components one at a time until the failure reappears. This helps identify which part is causing the issue.

Addressing printer power failures can be complicated due to the hands-on nature of the troubleshooting required. For this reason, we're not able to provide remote support or detailed repair instructions. However, we do offer in-person diagnostics and repair services at our local diagnostic facility (https://bchtechnologies.com/printer-repair-service). Please note that this service runs on a first-come, first-served basis, so depending on demand, it might take a few weeks to get your printer checked in. We can work on the entire printer or individual modules with clear next steps provided. That said, our services are not the cheapest option. Many customers find self-help through online tutorials or video guides to be the most economical starting point. I highly recommend using the search function on our YouTube channel homepage (https://youtube.com/@bchtechnologies), as we've covered many related repair scenarios over the years.

Thank you again for bringing us your question. Your engagement helps us continue supporting the printer repair community, and we truly value the trust you've placed in BCH Technologies.