caso de reparación
SG3525 sin PWM salida
Utiliza esta página cuando an SG3525-based soldadora placa de control has potencia but the PWM salidas are missing, locked, o too weak to drive the next etapa.
What must be true before replacing the chip
An SG3525 can be healthy y still produce no useful drive if its shutdown, realimentación, oscilador, arranque suave o salida path is being held in an abnormal state. Do not judge only by chip VCC.
Measurement sequence
| Node | Valor esperado comprobación | Significado de la falla |
|---|---|---|
| VCC y ground | Stable chip supply at the correct pins | Missing o pulsing VCC points to auxiliary supply o local regulator falla |
| Referencia salida | Referencia voltage present y not collapsed | Shorted external load o damaged IC |
| RT/CT oscilador | Timing ramp o oscilador activity | Open timing resistencia/capacitor o failed oscilador section |
| shutdown / arranque suave | Not clamped in shutdown state | Protection circuit, optocoupler o transistor is blocking PWM |
| salida pins | Alternating PWM drive present | If entradas are normal but salidas are dead, suspect IC o salida load |
diagnóstico flow
Confirm auxiliary rails
↓
Confirm SG3525 VCC y reference
↓
Comprobación oscilador pins
↓
Comprobación shutdown / arranque suave clamp
↓
Comprobación salida pins y driver load
↓
Only then replace SG3525 if needed
Common causes
- Missing auxiliary supply o bad local regulator.
- Shorted timing capacitor o cracked timing resistencia.
- Protection transistor holding shutdown active.
- Optocoupler realimentación path clamping the control loop.
- Shorted driver transistor loading the SG3525 salida.
- Cold solder joints around the IC socket o driver transformador path.