Dot-matrix printer maintenance: Which component should never be lubricated during routine service?

Introduction / Context:
Impact (dot-matrix) printers require periodic lubrication of certain mechanical parts to maintain smooth motion. However, the printhead contains precision pins and guides that must remain clean and dry. Lubricants can gum up the mechanism and cause failures. This question distinguishes serviceable parts from those that must not be oiled.

Given Data / Assumptions:

• The printer uses a pin-based impact head striking an inked ribbon.
• Some moving parts like carriage rails may need approved lubricants.
• The printhead assembly relies on precise, clean tolerances for pin movement.

Concept / Approach:
The printhead's pins move at high frequency through narrow jeweled or metal guides. Lubricants attract dust and ribbon debris, causing sticking, misfires, or bent pins. Manufacturers warn against lubricating the printhead; instead, it should be kept clean and replaced when worn. Carriage rails and selected bearings, by contrast, may be lubricated with approved light oils or greases per the service manual.

Step-by-Step Solution:

Verification / Alternative check:
Service guides and field bulletins specify “Do not lubricate printhead.” Units with oiled heads often show poor print quality and head failures.

Why Other Options Are Wrong:
Some printers do permit limited lubrication of carriage rails and specific bearings; the exact regimen varies by model, but the printhead is universally non-lube.

Common Pitfalls:
Using household oils that migrate, over-lubricating rails, or contaminating the ribbon path, all of which cause smears and jams.

Final Answer:
Printhead