Re: Metcal RF soldering base unit playing up.
The RF connector is Type-F
Once, when giving a talk, I covered what the different RF connector names meant and someone asked what 'F' stood for. "Very bad" I replied.
The metcal has an RF output stage whose power is controlled by a detector which is part of a directional coupler on the RF output. The winding on the heating part of the tip is wound so that it looks close to 75 Ohms when the metal core is below working tempaerature (the Curie point) at theat temperature, the impedance changes rapidly and the load ceases to be a match for the impedance of the directional coupler and coax (75 ohms) and so power is reflected from the tip back to the base unit. The base unit detector senses this and throttles back the power supply voltage reaching the power output stage.
If a tip fails in a way which changes its cool impedance (EG a shorted turn) then the impedance looks bad, relfected power holds the level of RF from the base down and the thing never gets to temperature. The mismatch is such that the tip cannot take the full designed power from the base, and also the base senses this and reduces the available power as well.
David
Oh, and the mains switch on top switches only the secondary of the mains transformer, so it's as well to shut off the power from the socket when not in use.
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