15 April 2010

IC-775 DSP overheated voltage regulators

Recently I had the opportunity to service a good friend's  IC-775DSP (an excellent quality rig, by the way). After completing my work, I noticed that two SMD voltage regulators in the middle of the PLL unit (at the underside of the rig) were getting very hot, to the point of discoloring the PCB around them. The venerable and extremely accurate index finger test confirmed the situation, and I had to let out a muffled cry, as my bold "probe" suffered the dire effects of the alarmingly elevated temperature of the ICs. I measured their output voltage and saw that it had dropped a bit from the nominal value - a common symptom with chronically overheated three-terminal regulators. So, I proceeded to install an improvised heat sink (see the photo, click on it to enlarge).

The heat sink is made from solid copper wire with a diameter of 1.5 - 2 mm. The wire is bent to a shallow "Π" shape (that's the greek letter "pi") with the proper dimensions and soldered to the tabs of the regulators and the adjacent shield cans, which thus become part of the heat sinking arrangement (don't worry, there aren't any heat - sensitive circuits in them). The poor regulators work at a far lower temperature now, which is good for their health and longevity - as the IC-775 DSP even in our digital era is definitely a keeper, with a high spec receiver that's a pleasure to listen to and a lot of conveniences for the operator - including a very effective DSP system.