Laser printer diagnostics: A laser printer outputs a completely black page. Which cause is most likely?

Introduction / Context:
In electrophotographic (laser) printing, several charging stages prepare and develop the image on the drum before transfer and fusing. Recognizing symptom-to-stage relationships speeds troubleshooting and parts replacement.

Given Data / Assumptions:

• Total page is uniformly black.
• Printer otherwise feeds and fuses normally.
• Focus on the most probable single-point failure.

Concept / Approach:
The primary charge (corona or charge roller) applies a uniform charge to the drum. The laser then selectively discharges areas to form the latent image. If the primary charging stage fails (no power to the primary corona/roller), the drum is not correctly precharged and tends to attract toner across the entire surface during development, producing a solid black page. By contrast, a failed imaging laser usually yields blank pages (no discharging, toner repelled), not black ones. Transfer issues affect how the image gets onto paper, not whether it is all black.

Step-by-Step Solution:

Verification / Alternative check:
Swap in a known-good charge assembly or perform engine test pages; service manuals list this symptom for primary charge failures.

Why Other Options Are Wrong:
Imaging laser malfunction tends to produce blank (white) pages. Low toner reduces density, not creates black pages. Transfer corona failure leaves image on drum or causes faint prints, not a solid black page.

Common Pitfalls:
Replacing toner unnecessarily or suspecting the formatter when the electrophotographic core is at fault.

Final Answer:
no power to the primary corona