On Fri, Aug 6, 2010 at 2:07 PM, Maglinger, Paul <[email protected]> wrote: > A place I worked had an electronic adding machine. ... something > like 8 PC boards, and each board must have had 100 transistors.
At $WORK, we have a measurement system (test equipment) known as an HP 8510. It's around 25 years old, but still in service. Here's what one looks like: http://a.imageshack.us/img101/8307/hp8510c.jpg It consists of four separate major components (enclosed chassis). Each major component has from 10 to 20 sub-assemblies, each with their own PCB, plus a power supply section, front panel, and rear panel, and backplane. Each sub-assembly is labeled with name and ID (e.g., "A19 REGULATOR"), on both sub-assembly and backplane. The manual includes function diagrams which show how it all ties together, along with component-level circuit diagrams. Last week, it suddenly failed self test. The diagnostic on the screen advised us which circuit boards were the most likely source of trouble. When the tech from Agilent came, he opened up the likely culprit. The power supply section consisted of a transformer, capacitor bank, rectifier board, and regulator board, all separate. Test points are provided and labeled. He used a meter to identify the -5V line as below tolerance. He found a bad connector where the transformer leads attached to the rectifier board. The unit is out of support and parts are hard to get. So he broke out his soldering iron, removed the connectors from wire and board, and soldered the wire directly to the board. That fixed it. It was a weird feeling, seeing something electronic actually repaired. I imagine people must have felt the same watching horse-and-buggy shops close down with the introduction of the automobile. -- Ben
