[fintstone]

There is not much to one of these. If I recall, that model has a dual position trigger for high and low heat. If it gets hot (but not hot enough) in both positions, the switch is likely good. All that is left is a simple transformer and the connections (other than the tip). These always have tip issues. The tip connections must be extremely tight and the tip in good shape as there are low voltage/high current. If thinning at the tip or dirty, it will not draw enough current. If you don't have a spare tip, you can use a piece of clean solid 12 ga wire to test (like from a ground wire). Put it in and tighten well. 14 gauge or lower is too small. Use pliers to shape it somewhat like the original tip. It should melt solder just fine.

Don't use these guns on circuit cards if you can help it as they get too hot (when working properly).