Nuts and Volts - September 2014

At 1A, expect to charge and run your phone without a problem since most cell phones — even on transmit — are below 1W output. Refer to: https://en.wikipedia.org/wiki/Mobile _phone_radiation_and_health and http://hypertextbook.com/facts/ 2006/ EbruBek.shtml.

Phil Karras KE3FL via email

[#8141 - August 2014]

Audio Mixer Question

I have a rather old audio mixer that has 1/4" inputs for microphones. The inputs are labeled "HiZ." I have microphones I'd like to use, but they have a three-pin "XLR" style connector. Do I need some kind of matching transformer, or can I just use a 1/4" male plug wired to some of the contacts on the XLR jack?

#1 For starter, you CANNOT use a 1/4" male plug wired to an XLR jack. The 1/4" line is unbalanced, meaning there is one signal line and a ground. The XLR line has two signal lines with opposite and equal signals plus the ground. Use a RadioShack model 274-016 (or equivalent) A3F XLR jack to 1/4" plug adapter. This adapter contains a balance-to-unbalance (balun) transformer to match the two lines properly. The balanced line and High Impedance (HiZ) are both used to reduce interference on low level signal lines like microphones.

Tim Brown PhD EE, PE Honea Path, SC

#2 Yes. You need an adapter to mate that "unbalanced" (Hi-Z) microphone input to a "balanced" (Low-Z) microphone. Here are three ideas: RadioShack sells item #274-016 (you'll need cables to connect the two ends). Here's the link: www.radio shack.com/product/index.jsp?prod uctId=2062443. Chances are your local Shack has it in stock.

Parts Express ( www.partsexpress .com) sells a similar adapter: www. parts-express.com/pyle-ppmjl15-1-4- male-to-xlr-female-mic-cable-15-ft--

248-4614.

If you're handy with a soldering iron, here's a DIY idea: www.media-college.com/audio/connection/xlr-jack-mono.html (all necessary parts are available at RadioShack).

All three methods will do what you need — just pick the option that's easiest for you to implement.

Ken Simmons Auburn, WA

[#8142 - August 2014]

Help Identifying an Old Robot

I picked up an old robot chassis at an estate sale for $25. I have taken some pictures in the hope someone might be able to identify the make/ model for me.

I am SO jealous! That is the RB5X robot made by RB Robotics in 1982. You can read more about this awesome robot on my website at www.robotsandcomputers.com/ robots/ rb5x.htm or at this other great site at www.theoldrobots.com/ rb5x.html. I hope you enjoy your very impressive find! I'm still looking for one of my own.

Derek Tombrello via email

[#8143 - August 2014]

iPod Battery Reconditioning

My son has gifted me with his cast-off iPod Classic 30 gb player. Unfortunately, the battery life is only about 15-20 minutes of playing before it goes dead. Does anyone know of a way to recondition the battery?

#1 Forget the old battery and buy a new Lenmar replacement battery for the iPod Classic 5 G ( 30 Gb) This battery replaces 616-0230 and EC008-2. Amazon carries them for around $15. The Portable Rechargeable Battery Association (PRBA) highly recommends against using reconditioned lithium-ion batteries, and I would assume this also applies to lithium-polymer batteries due to their propensity for catching fire. I found one website that advocated a repeated freeze and charge process, but for $15 I would buy a new known battery versus trying to resurrect a possibly defective unit.

Tim Brown PhD EE, PE Honea Path, SC

#2 The first iPods were famous for the irreplaceable battery, and they are extremely hard to open. IFixit considers the iPod Classic battery replacement "very difficult," and you can find some YouTube videos on opening and replacing the battery if you dare to do it yourself.

If you wish to continue using your son's iPod Classic as a portable music player but don't want to risk damaging it, consider attaching a portable external battery. If your iPod Classic uses a USB cable to charge, then buy an external USB battery which can supply five volts and at least 0.85 amps (850 milliamps). Some are as large as the iPod, so just tape it back-to-back, and use the shortest USB cable between them. They are rechargeable from any other USB port, and will be useable with smartphones if you desire to retire that iPod.