OK, I admit it. I’ve made mistakes that have led to blown power supplies and blown inputs and outputs on some of the equipment that I’ve worked on. You don’t have to make those same mistakes, though, if you follow these simple tips. Don’t blow it!
Check the voltage AND polarity of a replacement power adapter. Many instruments these days are using external power adapters, or “wall warts,” to provide power. Using a replacement adapter sounds easy enough, but not so fast. Not only do you have to ensure that the replacement adapter has the appropriate output voltage, but also that the output connector is wired properly. For some adapters, the center pin is positive and the outer conductor negative. For others, it’s the exact opposite, and I needn’t tell you that connecting plus to minus and minus to plus can cause major problems. So, before you use a replacement adapter, check the polarity of the center conductor to make sure the polarity is correct.
Check input voltage settings. If your instrument is AC-powered, make sure that the input voltage setting is correct before turning it on. Connecting 220 VAC to a power supply configured for 115 VAC could cause internal damage, smoke, or even worse, a small electrical fire.
Let it dry. If you clean PC boards or electrical contacts with isopropyl alcohol, make sure to let it dry completely before turning the equipment back on. Isopropyl alcohol contains water, and that water can cause short circuits that will damage the equipment. To let the equipment dry completely, go to lunch, work on something else for an hour or so, or even better yet, let it dry overnight.
Check your connections. It’s very easy to make the wrong connections when setting up a system with several different instruments. For example, say you have a rack of equipment, with instruments stacked on top of each other. You go to check the output of your signal generator and plan to hook it up to your spectrum analyzer. Whoops, you accidentally hook up one signal generator to another signal generator. This can blow the output of one of the signal generators. You can avoid this by turning off the signal generator outputs until you have had a chance to double check all your connections.
Check input ratings. Network analyzers are designed to handle the outputs of their tracking generators. In some applications, though, you may want to use an external signal source. If you do this, make sure to not exceed the input RF rating of the network analyzer. It’s very easy to blow the input port of a network analyzer by applying too much power to the port. Similarly, you can blow the input of an oscilloscope by applying too much power to it. Don’t blow it! Check the input specs first.
Properly load your equipment. It’s very easy to blow the output of an RF amplifier by not properly loading the output. Inputs should be properly terminated, too. Believe it or not, this happens all too often. It has happened to me. Even if the manual states the amp has protective circuitry to prevent this from happening, don’t take the chance. Always connect a dummy load with the correct impedance to an amp before turning it on. For extra safety, put a load on the input as well.
Minimize static electricity. ESD is the silent killer. It gets everybody. To prevent ESD from blowing your equipment, make sure you are properly grounded. When working with electronic equipment, you should wear grounding straps on both of your shoes and use a properly grounded wrist strap, too. Other steps that you can take include equipping your lab with flooring, benches, chairs, and carts designed to dissipate ESD. Also, check the humidity in your work area; be extra careful with low humidity as it increases the chance of static electricity.
Now that I’ve come clean, I’d like to hear about your experiences. Please share them here. Let’s help each other not “blow it!”!
At Axiom Test Equipment, our job is to ensure that you get the most out of your test equipment. If you have any questions about test equipment repair or preventive maintenance, please feel free to contact us via email at firstname.lastname@example.org or phone 760.806.6600.