Fig. 1: Use a muffin tin to hold hardware.
Fig. 2: The DA is ready to reassemble; the muffin tin holds all the nuts and bolts. At one time or another, you’ve reassembled equipment and were either short pieces of hardware or had hardware left over.
Mark Voris is a frequent Workbench contributor and the engineering manager for the Spirit Catholic Radio Stations, based in Omaha, Neb. Mark writes that he finally found time to do some bench work, and had two Asymetrix 581 distribution amplifiers that were in need of repair.
He finds that keeping mounting screws organized while doing this work can be trying. His solution was a labeled muffin tin. Using the tape labels ensures the right hardware is replaced properly — and the muffin tin is no worse for the wear.
Mark adds that this is the first time he’s attempted to work on surface-mount devices. He didn’t have the right soldering iron or optics, but replaced capacitors and regulators nonetheless, and the amps work fine. In other words, no factory installed smoke was detected!
Do-it-yourself enthusiast Charles “Buc” Fitch, P.E., writes in with an MCM corollary. While you’re buying those MCM audio amp bricks we mentioned, Buc points out another interesting item that the company has on sale. See it at www.mcmelectronics.com by typing part number “58-17903” in the search field.
Fig. 3: This MCM “guts pack” makes for a great stocking stuffer. Described as an electronic survival guts pack, this little bag contains about 60 basic components, of which the most useful is a small proto-board. This is a valuable item to mock up small circuits before committing them to final construction. Buc’s thinking of those little interfaces on remote controls and mini-relays activated by other functions.
At a sale price of $3.99, the value of the components in the bag easily exceed this cost, so it’s a good buy no matter what your current needs are. Consider this a great stocking stuffer for your techno-geek buddies.
Speaking of gifts, one of Buc’s favorites for friends is an inexpensive, yet flexible, small digital meter for your car or truck glove compartment. How often have you encountered a simple tech challenge (“Why is my mother-in-law’s refrigerator not working properly?”), but you are annoyed because you could have fixed it easily, if you’d just had your meter with you? A useful gift, often available for under $10.
You could also add the MCM survival kit to the glove compartment, along with that meter.
Fig. 4: The switching problem was traced to a defective U25.Fig. 5: The inside of the LX-1. U25 is circled in red. Bible Broadcasting staff engineer Steve Tuzeneu checked out a Burk LX-1 audio switcher he was installing and noticed that the switcher would “mix” all of the inputs selected and not select a single audio channel.
He checked to make sure the “ready” light was on and the mix feature was off, as it is supposed to be. After some trouble-shooting, Steve replaced U25, a chip with the number CD4011UBE. This is a quad dual input NAND Gate IC. The inside of the LX-1 chassis is shown in Fig. 5, with U25 circled in red. Replacing the chip restored operation, permitting the LX-1 to select only one channel at a time, as intended.
An oscilloscope, or even the inexpensive DVM that Buc recommended, can be used to troubleshoot logic like this.
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Author John Bisset has spent 46 years in the broadcasting industry and is still learning. He handles West Coast sales for the Telos Alliance. He is SBE certified and a past recipient of the SBE’s Educator of the Year Award.