Aunt Judy: Beware relatives' repairs
Engineers tend to get a lot of requests to fix electronic devices for friends and relatives. These tips will help you keep your sanity without letting down Aunt Judy.
By Howard Johnson, PhD -- EDN, November 8, 2007
Old Aunt Judy approaches you at a wedding reception and, with a halting voice, says, “You know about computers, right? Well, I've got this old eight-track-tape player [or black-and-white television, turntable, or whatever], and it isn't working too well any more. Can you take a look?”
Ridiculous? Yes, but try explaining to her the difference between the high-speed-digital miracles you create at work and the old, transistorized audio anachronism she wants you to fix. You can't. And you don't really want to. Aunt Judy expressed confidence in your abilities, and this is not the time to let her down. Fortunately, I am here to give you some tips. I have a lot of experience in this area. (I have a lot of relatives.)
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Rule 1: Unless you have nerves of steel, do the work at home, alone, and away from the supplicant. Take your time.
Rule 2: I know it is difficult, especially with “snap-together”-style plastic cases, but try not to break the case during disassembly. Keep some superglue handy. It must be fresh. I keep mine in the refrigerator. For most plastics, I like the kind of cyanoacrylate glue—typically sold under trademarks such as Superglue and Krazy Glue—that comes with a glue activator.
Rule 3: Don't lose any parts. Sweep the floor before you start work. I work on a table top made of white-board material. I write a note by each little pile of screws that says where they go, and I tape the screws to the table top. Plastic bags and baby-food jars work just as well.
Rule 4: Take pictures with a digital camera. You will later thank yourself if putting the product back together becomes confusing.
Rule 5: Test one small section of the product at a time. This step usually requires a signal source to stimulate each section and a detector to observe its output. When working on audio products, for example, I use a small voice recorder as the signal source and a sensitive pair of headphones, with a preamplifier if necessary, as a detector. If you have an ac-coupled headphone, you can use it to “listen” to hum on the dc-power rails.
Rule 6: Cheat. If the product was once popular, you can probably find the schematics for it online. This rule has a subrule: Never promise a fix date. You need time to find those schematics, advice, or whatever.
Rule 7: Buy a replacement on eBay. Do not give Aunt Judy the replacement, because she will know that it isn't hers. The new one will have scratches in different places. Just use the replacement as a benchmark, comparing the broken set against the original in every particular. The replacement also gives you a source of spare parts. When you are done, throw it away. You are not building an economically efficient repair business here, just saving some face—and, possibly, impressing your cute cousin.
Rule 8: In older transistorized products, the problem likely involves conductive dirt, corroded connectors, or a power-supply malfunction—that is, unless someone has dropped or spilled milk into the product. So, blow out the dust with a can of compressed air, scrub the board with a cleaner from CRC Electronics, polish all the connections, and check the power supplies. Those steps will fix 90% of your problems. For the other 10%, you can go on the Web to buy replacement drive belts and needles for any turntable. And plenty of people still sell old CRTs, and, yes, you can still buy eight-track tapes.
Rule 9: To solve a power-supply problem, first substitute a good external supply. If the PCB (printed-circuit board) does not indicate the correct dc-supply voltage, then set your external voltage at approximately 60 to 80% of the rating printed on the bypass capacitors in the circuit. By the way, old capacitors become highly unreliable as they age. Some people just replace them all as a precautionary step.
Rule 10: Never accept Aunt Judy's money. Doing so will lock you into a lifetime of repair work with your whole family. Instead, trade her for something she's really good at—like baking cherry pies.
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I've enjoyed this article very much. After fixing different electronic products from friends and relatives for the last 30+ years, I can really relate to the Howie's rules. It was much more difficult to find needed information in the pre-Internet era, however, most products were relatively easily repairable. With integration level of new gadgets reaching new heights, it is increasingly more difficult to fix broken stuff. I think not too many people can find a replacement for a special ASIC or remove and resolder a fine-pitch 180+ pin part on the board. Oh well, this is called progress, you can't fight it.
Anushavan Atanasian - 2007-17-12 15:37:00 PST -
Howard,
This is excellent and timely advice for those on this particular road to perdition. I would add one bit of cautionary advice however, and that is to work on a static free surface. Much of the older equipment had no input protection. Discrete transistors especially were quite vulnerable. A cookie sheet (bare metal - not non-stick)grounded would work fine.
Dave Koza
Dave Koza - 2007-20-11 09:53:00 PST -
Fun article. Took me back to my first electronics class in college (1970). The professor started off as follows. You are now starting your career in electronics. At Sunday lunch aunt "Judy" will ask you to fix her radio (tape player etc.). Take the radio and when you put it on the bench apply full AC across the battery terminals and destroy it completely. Within hours your entire extended family will know how useless you are and you can complete your college education without having to do annoying favors for friends and family.
Paul Michelow - 2007-19-11 22:22:00 PST -
If you find a working duplicate on eBay, swap out the housing and call it a day!
David Hostetler - 2007-16-11 11:57:00 PST -
Great article! I especially like the suggestion of using dry-erase board for the top of the workspace. Beware, even fixing the first gadget for Aunt Judy (even if no money changes hands) will probably consign you to another call when the next gadget breaks.
There is another great and inexpensive solution to managing all the screws and other small parts: Plastic ice cube trays. Pick a system (clockwise, top-to-bottom, etc.), a separate cube for each type of part, and the parts will always be sorted in the order they were removed. Plus, they won''t get out of order if they get elbowed aside for a bit more table room (a common problem I had with baby food jars!)
Tim Gipson - 2007-15-11 14:25:00 PST
