Miller Bobcat 250 NT User Manual (English)

Questions and Answers:

A
Allison HoldenJul 26, 2025
Why is the weld output erratic on my Miller Inverter?
- D
  Dillon SanchezJul 26, 2025
  If your Miller Inverter's weld output is erratic, try the following: * Check the control settings. * Ensure connections to the electrode and workpiece are tight and clean. * Use dry, properly stored electrodes for Stick and TIG welding. * Remove excessive coils from weld cables. * Clean and tighten connections both inside and outside the welding generator. * Check and adjust the engine speed if necessary. If the issue persists, have a Factory Authorized Service Agent inspect the brushes, slip rings, and integrated rectifiers SR2 and SR3.
C
colemankatherineAug 3, 2025
How to fix low weld output on my Miller Bobcat 250 NT Inverter?
- B
  Bryan RobinsonAug 3, 2025
  If your Miller Inverter has low or no weld output but the generator power output is okay at the AC receptacles, consider the following: * Check the control settings. * Check the weld connections. * Inspect fuse F1 and replace it if it's open. If the problem continues, have a Factory Authorized Service Agent check the brushes, slip rings, and integrated rectifiers SR2 and SR3.
J
justinmurphyAug 10, 2025
What to do if my Miller Inverter has no weld or generator power output?
- M
  Michael BlakeAug 11, 2025
  If your Miller Inverter has no weld output or generator power output at the AC receptacles, try these steps: * Ensure all equipment is disconnected from the receptacles when starting the unit. * Check fuses F1 and F2, replacing them if they are open. * Check the connection of plug PLG6. If the issue persists, have a Factory Authorized Service Agent inspect the brushes, slip rings, and integrated rectifiers SR2 and SR3.
D
Debra TurnerAug 18, 2025
How to decrease high weld output on my Miller Inverter?
- J
  Joshua WrightAug 18, 2025
  If your Miller Inverter is producing high weld output, you should: * Check the control settings. * Check the engine speed, and adjust it if necessary.

Miller Bobcat 250 NT Specifications

General

Input Voltage	120/240 V
Fuel Type	Gasoline
Duty Cycle	100%
Frequency	60 Hz
Noise Level	68 dBA at 7 m
Input Phase	1-Phase

Summary

Safety Precautions - Read Before Using

Arc Welding Hazards

Details potential hazards associated with arc welding processes.

Engine Hazards

Outlines potential dangers and precautions related to the engine.

Specifications

Weld, Power, and Engine Specifications

Details the welding output, power ratings, and engine specifications of the unit.

Duty Cycle

Installation

Installing Welding Generator

Covers proper placement, airflow, and grounding procedures for generator installation.

Engine Prestart Checks (Onan-Powered Units)

Engine Prestart Checks (Kohler-Powered Units)

Connecting the Battery

Connecting to Weld Output Terminals

Operating the Welding Generator

Front Panel Controls

Identifies and explains the function of each control on the welding generator's front panel.

Typical Stick Welding Connections and Control Settings

Guides on connecting and setting controls for Stick (SMAW) welding processes.

Typical MIG Welding Connections and Settings

Provides typical connections and control settings for MIG (GMAW) welding, solid wire applications.

Self-Shielded Flux Core Wire Applications

MIG Connections and Settings with Weld Control and Spoolgun

Operating Auxiliary Equipment

Standard Receptacles

Maintenance (Onan-Powered Units)

Routine Maintenance (Onan-Powered Units)

Outlines routine maintenance tasks and recommended service intervals for Onan engines.

Servicing Air Cleaner (Onan-Powered Units)

Changing Engine Oil, Oil Filter, and Fuel Filter (Onan-Powered Units)

Step-by-step guide for changing the engine oil, oil filter, and fuel filter.

Adjusting Engine Speed (Onan-Powered Units)

Maintenance (Kohler-Powered Units)

Routine Maintenance (Kohler-Powered Units)

Outlines routine maintenance tasks and recommended service intervals for Kohler engines.

Servicing Air Cleaner (Kohler-Powered Units)

Changing Engine Oil, Oil Filter, and Fuel Filter (Kohler-Powered Units)

Step-by-step guide for changing the engine oil, oil filter, and fuel filter for Kohler engines.

Adjusting Engine Speed (Kohler-Powered Units)

Troubleshooting

Welding Troubleshooting

Guides for diagnosing and resolving issues related to weld output and quality.

Generator Power Troubleshooting

Guides for diagnosing and resolving problems with generator power output.

Engine Troubleshooting

Provides solutions for common engine starting, running, and power issues.

Generator Power Guidelines

Grounding Generator to Truck or Trailer Frame

Grounding to Building Systems

Equipment Power Requirements

Motor Starting Power Requirements

Generator Power Supply Capacity

Connections for Standby Power Supply

Stick Welding (SMAW) Guidelines

Stick Welding Procedure

Step-by-step guide for performing stick welding, including setup and technique.

Electrode and Amperage Selection Chart

Table for selecting appropriate electrodes and amperage settings for various welding conditions.

Striking an Arc - Scratch Start Technique

Striking an Arc - Tapping Technique

MIG Welding (GMAW) Guidelines

MIG Connections: Voltage-Sensing Wire Feeder

Diagrams typical connections for MIG welding using a voltage-sensing wire feeder.

MIG Connections: Constant Speed Wire Feeder

Diagrams typical connections for MIG welding using a constant speed wire feeder.

MIG Process Control Settings

Provides guidelines for setting wire size, amperage, wire speed, and voltage for MIG welding.

Holding and Positioning Welding Gun

Conditions Affecting Weld Bead Shape

Poor Weld Bead Characteristics

Good Weld Bead Characteristics

Troubleshooting - Excessive Spatter

Identifies causes and corrective actions for excessive spatter in MIG welding.

Troubleshooting - Porosity

Identifies causes and corrective actions for porosity defects in MIG welds.

Troubleshooting - Excessive Penetration

Identifies causes and corrective actions for excessive penetration in MIG welds.

Troubleshooting - Lack of Penetration

Identifies causes and corrective actions for lack of penetration in MIG welds.

Troubleshooting - Incomplete Fusion

Identifies causes and corrective actions for incomplete fusion in MIG welds.

Troubleshooting - Burn-Through

Identifies causes and corrective actions for burn-through in MIG welds.

Troubleshooting - Waviness Of Bead

Identifies causes and corrective actions for wavy bead appearance in MIG welds.

Troubleshooting - Distortion

Identifies causes and corrective actions for distortion in MIG welded materials.

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Table of Contents