20121026

Fix-it Night 10/18/12 - Tips and Pics

Last Thursday, we had our first ever "Fix it Night" at the shop. Basically, we encouraged everyone to bring their non-working electronics over and we'd all try to fix them. It was a success. This time, we did the following:
  • Replaced the joystick connector on an Atari 2600 console
  • Found and replaced a bad electrolytic capacitor in a 12V-to-110V power inverter. A suitable replacement was harvested from an old ATX power supply, and the unit came right up.  Yet another victim of the capacitor plague was spared from the landfill.
  • Replaced an 0603 surface-mount fuse in a Sony DS portable game console
  • Figured out why a 60" DLP television wasn't powering up and helped Queeg order parts for it.
Troubleshooting electronics really isn't that hard.  Knowing some basic electronics theory and hands-on skills can provide a lifetime of free TVs and DVD players, less stuff wasted, and a sense of satisfaction when you troubleshoot and fix something.

The important skills to work on are:

 1. Safety (Being able to identify the high-voltage sections and avoid them, knowing how to discharge the capacitors, working with one hand in pocket when devices are under power, etc. ) Sam's LASER FAQ has a great section on safety.

2. Disassembly (Finding the hidden screws, using a guitar pick to spread open plastic cases, heat guns to soften glue, etc). Many sites offer free"teardown guides" for specific products. These are especially helpful for phones, laptops, and other tightly-packaged electronics.

3. Board and Component ID - Figuring out what's inside and what is likely broken is mandatory before trying to fix it. Power supply issues are common and often easy to fix as they use big, simple components. If the device is "stone cold dead," it could be a simple component like a fuse, capacitor, diode, or similar. Tiny little logic boards filled with proprietary chips are not so good for DIY repair.
Lots of good info on component ID is here.


4.  Use of multimeters and other test equipment.  Identifying test points and checking voltages is a good place to start.  Many devices (flat panel televisions, for instance) use a generic power supply board that has all of the voltage inputs and outputs labeled. Troubleshooting caps with an ESR meter is another great skill to have here as well.  We picked up the Anatek Blue kit from Amazon and have had good results.

5. Power system troubleshooting - this includes fuses, connectors, diodes, capacitors, transistors, and other high-power components. If a fuse is bad, there's probably a reason, so it's best to identify any other obvious problems before just replacing and powering up.

6. Soldering and rework - Very old PCBs can be fragile and require careful use of the iron to avoid lifting the Copper traces. Small SMT  parts are often easier to work on with a pair of hot tweezers, hot air pencil, and a magnifier. All soldering should be done with a decent temperature-controlled iron. We like Metcal and Edsyn, but many affordable (US$50 range) alternatives exist. Pro-tip: Adding some lead-based solder to a lead-free joint will make it wet and desolder much easier.

7. Finding manuals, on-line forum posts and other resources. Often times, a quick web search with terms like "Toshiba DLP televesion white streaks" will net a wealth of useful information. Certain models tend to have the same things go wrong over and over.

Components can often be exactly identified by part number. Distributors like Digikey, Mouser, and Newark/Element 14 have extensive data sheet archives and links to helpful info.

Here are some pictures:

Desoldering the old Atari 2600 DB9 connector. Date on the PCB was 1980.

Arclight and some other folks hanging out by the Metcal 

Alan Rice talking troubleshooting theory with the group.






1 comment:

  1. Thanks for the post. Had a great time fixing stuff and learning from Arclight and Alan. Fixing the power inverter also lead me to figure out that the fuse in my car also went bad. Thanks guys see you at the next one hopefully soon!

    ReplyDelete