CompuServe Messages

Umm, well, there is this story about a hifi amplifier that, once the original complaint was fixed, hummed like a banshee in the shop and couldn't be tracked down; it just seemed to "pop into existance" in one of the preamp stages. Frustrated and beaten, the tech called a friend's shop across town, then drove over with the unit to see if HE could fix it. Upon arriving, it was clean as a whistle; drive back to home base, hum like a banshee, back across town, quiet again. The tech finally found it by leaning over the amp to get a good look in a nook he hadn't examined before and noticing that the hum level went way down. Turns out that there wasn't enough black die in the epoxy casing of one of the preamp transistors, and as we all know, silicon junctions are sensitive to light. The reason it only acted up at the home shop? His shop had fluorescent lights, his friend had incandescents. Why hadn't the customer complained about it? BECAUSE HE NEVER OPERATED IT WITH THE COVERS OFF! Life is strange. Service and maintenance careers are stranger. Rick