Abstract: A preheater for a wave soldering machine has high volume convection heating permitting components on circuit boards to be heated to more uniform temperatures throughout the assembly and more rapidly without damage to the components, the assemblies or both. The machine comprises a conveyor for circuit assembly boards, a housing through which the conveyor passes having an entrance and an exit, and a plurality of heating zones in the housing extending along the conveyor. Dividers are provided between heating zones and apertured heating panels are disposed in each of the zones with a space behind each of the panels and a recirculating gap around each of the panels. A fan is positioned in the space behind each of the panels for recirculating gas, either air or inert gas through the panels and the recirculating gap.