A power module cartridge for a welder includes a chassis tray that is dimensioned to fit inside an external case of the welder. The chassis tray includes a fan receptacle, a capacitor receptacle, a rectifier mounting slot and a transformer receptacle. A fan fits into the fan receptacle; a capacitor fits into the capacitor receptacle; a rectifier plate fits into the rectifier mounting slot; and a transformer fits into the transformer receptacle. The chassis tray can also include a clip for receiving a printed circuit board (“PCB”). The PCB can be electrically connected to the aforementioned components. A second chassis tray can fit on the top of each of the components such that the components are sandwiched between the first and second chassis trays. A method of manufacturing a welder is also disclosed.