Depending on the model, the circuit board can't really do much except turn the solenoid valve on or off so a weak flame should be due to something else. There are two valves in series (for safety) so possible that one of the valves is not opening fully.
Have you physically unscrewed the orifice to check that it really is clear and the housing that it screws into isn't full of debris
Tony Lee - International Grey Nomad. Picasa Album
- Travel Map
RVs. USA - Airstream Cutter; in Australia - MC8 40' DIY Coach conversion & OKA 4x4 MH; in Germany - Hobby Class C; in S America - F350 with 2500 10.6 Bigfoot camper