Bench Test / WeldKing / MAG255

Test intent

Separate crater-fill, discharge-path, spool-gun, and control-branch complaints from true internal board faults.
Confirm stable plain-steel MIG baseline before retesting spool-gun or aluminum branches.
Prove pins 1 and 9, post-trigger stop behavior, and wire-tip safety before deeper teardown.

Tools and setup

Digital multimeter
Clean steel coupon
Known-good work clamp
Plain-steel MIG gun with fresh consumables
Spool gun only if the complaint is aluminum-only or one-gun-only

Pre-power checks

Check	Expected condition	Result
Gun, liner, and tip baseline	chart-correct plain-steel base-gun setup with clean feed path	pass / fail
Crater-fill branch as found	documented before any diagnostic change	pass / fail
Polarity and output lead placement	correct for active process	pass / fail
Spool-gun branch if attached	isolated and not affecting base-gun proving	pass / fail

Electrical and control checkpoints

Checkpoint	Expected value or behavior	Record actual
Spool-gun pins `1` and `9`	welding voltage present only when spool-gun branch is selected
Post-trigger stop behavior	wire stops cleanly, not creeping after release
Wire-tip behavior with no trigger command	no unexpected spark or discharge event
Base-gun versus spool-gun branch	base gun proves first, then spool gun only if required

Functional proof

Test	Pass condition	Result
Normal startup	no abnormal breaker trip or immediate fault state	pass / fail
Trigger feed baseline	feed starts only on command and stops cleanly	pass / fail
Plain-steel MIG weld	stable short weld with normal arc quality	pass / fail
Re-trigger behavior	no abnormal run-on or delayed stop beyond normal expectation	pass / fail
Spool-gun check if required	only fails if complaint genuinely follows that branch	pass / fail

If it fails

Wire creeps after stop: stay in crater-fill branch first.
Sparks appear at the wire tip without trigger command: stay in discharge-path resistor branch.
Base gun healthy but spool gun bad: stay in pins 1 and 9, spool-gun, and drive-roll branch.
Intermittent feed surge remains after external proving: stay in documented PCB or control branch.

Direct official parts pages

Use these only after the complaint has already been proven to follow an external gun, spool-gun, or drive-roll branch.
MAG255 parts category: official MAG255 parts path
SpoolKing24D spool gun 07NS1000: official product page
U-groove aluminum drive roll 07000302: official product page

Post-repair release

Signoff item	Result
Base MIG baseline restored	pass / fail
Stop behavior and wire-tip safety restored	pass / fail
Chart-correct base-gun weld restored	pass / fail
Spool-gun branch behaves normally if required	pass / fail
No abnormal run-on, discharge, or breaker trip after power cycle	pass / fail

Technician: __________ Date: __________ Serial or shop tag: __________