Model reference
Panasonic YC-300TSP TIG Welder Repair Reference
Model reference for Panasonic YC-300TSP TIG service routing, focused on high-frequency start, low OCV, SCR phase-loss checks and current-feedback symptoms.
Database summary
The YC-300TSP is a Panasonic TIG platform whose high-frequency start and SCR-controlled output faults can be separated by service tests around the HF circuit, main-control P-board, contactor path and thyristor gate-cathode resistance.
This page is a model hub. Use the dedicated diagnostic workflow for no-HF, weak HF, low open-circuit voltage, SCR phase-loss checks and pulse-current indication faults.
Key service areas
| Area | Reference evidence | Interpretation |
|---|---|---|
| HF start circuit | CR2 contact, HFTr transformer, C5 high-voltage capacitor and SG spark gap. | No HF may be P-board command failure or actual HF-circuit failure. |
| 35 to 42 bypass distinction | Short 35 and 42 on the main control P-board under controlled conditions. | If HF appears, suspect the main P-board; if not, inspect the HF circuit itself. |
| Open-circuit voltage | DC OCV reference about 57V; secondary phase voltage about 42V AC. | Low OCV routes toward input phase, contactor, SCR module, SCR protection board or P-board. |
| SCR phase-loss check | 8-18, 10-20, 9-19, 12-22, 11-21 and 13-23 should read about 30–40Ω. | Higher resistance or open circuit points to that SCR/protection branch. |
| Current indication mismatch | Shunt overheating and oxidation can distort feedback. | Panel current evidence must be checked against output and shunt condition. |
Typical fault notes
- HF sometimes present can be caused by low or unstable input voltage; treat 380V ±10% as the starting supply check.
- HF inside the machine but not at the torch points to long torch leads, loose output terminals, insulation damage or HF leakage to the chassis.
- Pulse-current indication without expected bead pattern can come from poor output cable contact, not necessarily pulse-control failure.
- Immediate breaker trip after power-on should route toward SCR module damage.