|
Do not forget to check for bad solder joints.
I find when something works fine for years and then starts acting up, it can usually be a bad solder joint.
Following is a list if items I have sorted bad solder joints on recently:
House gas fired power vent hot water heater controller, really did not want to spend $200 for a new controller on an 8 year old water heater that I plan to replace in the next few years anyway.
Fax machine, worked fine until I moved. Cold solder joints acted up after unit was moved.
Many audio components, DBX units, audio amps, processors.
5 year old factory Ford CD/Cassette unit with intermittent dimming, missing display (fixed this Sunday night!) Searched info on the net, pulled unit, re-soldered and re-installed in less than 1 hour, problem solved!
Circuit boards for pinball machines
All kinds of kid’s battery powered toys made in China. Talk about poor soldering work, these items are the Prize Winners!
And many other items I cannot think of at this moment.
Have you moved your gear lately? This is usually a good indication that you might have a bad solder joint somewhere.
When you open the unit, look around relays and power resistors on the circuit board for heat discoloration. Also look closely at the bulkhead connectors on the circuit boards. I usually find the bulkhead connectors are prime suspects for poor solder joints if I do not find any heat discoloration.
I usually find cold solder joints are for 2 main reasons:
1. Boards are now mostly surface mount, but larger components and connectors are still through hole design. The larger components need more heat to get a good solder joint as they tend to act as a heat sinks with too much mass for the wave soldering or IR machines. I almost always retouch all through hole items on mixed surface mount/through hole boards.
2. Inspect around all larger power resistors carefully. Many times they get very hot and transfer the heat to the solder joints, circuit board and surrounding components. The heating and cooling cause’s board expansion and contraction which can cause surface mount items in the near area to break solder joints. You will usually find power resistors in the power supply section, battery charging sections and sometime around relays.
I would also look for fuses as well.
Get a good light and magnifying glass, but when it doubt retouch everything if it is not too time consuming!
Good luck!
JamesO
|