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mrf458 [2013/03/18 18:58] n1eu |
mrf458 [2013/10/16 09:41] n1eu |
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| The MRF 454 has a higher gain at 30 mhz: 90 watts for 5 watts of drive while the MRF-458 is spec'd at 70 watts for 5 watts of drive. | The MRF 454 has a higher gain at 30 mhz: 90 watts for 5 watts of drive while the MRF-458 is spec'd at 70 watts for 5 watts of drive. | ||
| The 1994 data book lists the MRF-454 as a direct replacement for the MRF-458. | The 1994 data book lists the MRF-454 as a direct replacement for the MRF-458. | ||
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| + | ===Soldering=== | ||
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| + | A bigger (higher power) iron means more heat capacity and faster heating, so less time to destroy things. A 35 watt is fine. I would not try a 15 watt. Even if it is temperature controlled, the big wide tabs and PCB copper will sink the heat from the iron and drop the temperature below the set value of the iron. But you do not want a higher temperature, which will burn things up, like the PCB material, or separate the copper from the fiberglass. What you want is a chisel tip (sometimes called screwdriver tip) as wide as the collector tab on the transistor, on a temperature controlled soldering iron. It does not need to be an adjustable temperature iron, but it should be a temperature controlled iron. The difference is that with a temperature controlled iron, you select a tip (I'm thinking of Weller WTCP and similar irons) that gives you a fixed temperature. With an adjustable one you have a knob (or up/down buttons) and a readout that lets you set it. In either case you want about 700 to 750 Fahrenheit. If you use too low a temperature you mess around too long and damage things. If you use too high a temperature you burn stuff up. | ||
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| + | You want to get in, melt the solder, and wick it away quickly, and get out before you cause a lot of damage. | ||
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| + | I suggest you find some scrap piece of equipment that has large pieces of copper (similarly sized as the power transistor tabs) soldered to the PCB and practice a bit unsoldering and resoldering on the expendable piece of scrap, before you get into your PA. | ||
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| + | DE N6KB | ||
