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mrf458 [2013/10/16 09:41] n1eu |
mrf458 [2013/10/16 09:44] n1eu |
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| ===Soldering=== | ===Soldering=== | ||
| + | while every tech has his or her own style, here's how I do it. | ||
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| + | you're 35 watt iron should be fine. You don't want to lift the copper from the board! | ||
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| + | while the soldering iron is warming, draw, photograph or take some kind of notes so you know what goes where. Most likely you'll need to unsolder feedback capacitors and resistors, so make damn sure you know where they go. | ||
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| + | you'll need some, make that lots, of solder wick. Get the good stuff and not from china. You want it at least 1/4 in wide. | ||
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| + | suck up as much as you can and then try and get even more off the pcb. | ||
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| + | then when a sharp knife (I use an xacto) slip under the tabs and with heat applied to loosen any left over solder, gently lift the tabs up from the pcb | ||
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| + | the collectors have the tip of their tabs cut at an angle. Make sure you document how the transistor (S) go in. They can easily be flipped 180 deg and you'll never know it. | ||
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| + | I don't recall what they used for the pa, but get some thermal goo and apply a thin layer onto the heatsink and device. Thin is better than a big glop. | ||
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| + | I go for the base first. I can then use a VOM to do a resistance check on the remaining leads. Bet you'll find a base to collector short. | ||
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| + | And while I'm in there, I'll lift the base leads of the drivers and look at them as well. | ||
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| + | I've had great success using my weller WTCP iron with a 35 watt element and a large chisel tip. | ||
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| + | and you need lots of solder wick. | ||
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| + | the two emitter leads are the hardest as they are mounted to the largest amount of copper on the pcb | ||
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| + | mike, wb8vge | ||
| + | ------------------------- | ||
| 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. | 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. | ||
