Just following directions....
Back when I was a young military man, I worked on flight simulators. I have lots of stories about expensive screw-ups.

For example, I once sat down on a $40,000 circuit board -- not my fault, they shouldn't have set it on the chair. I also accidentally erased Europe from our radar database by sneezing while adjusting a hard drive.

However, the most expensive was when a co-worker set all the power supplies on one of the simulators to 'nominal' values. Part of maintenance was checking all the power supplies -- you would check to see if the 15 volt power supply was actually at 15 volts, plus or minus some amount like 0.25. Such that if the power supply was anywhere between 15.25 volts and 14.75 volts, it's all good.

This lad misunderstood, and proceeded to adjust all the power supplies to read perfectly in the middle. The 15 volt power supply read exactly 15 volts, the 28 volt power supply read exactly 28 volts, etc. He did this to several dozen power supplies. Now, for parts of the simulator this was no big deal, they were all digital and worked fine anywhere in the proper range. Other parts, however, were highly sensitive to their input voltage.

For example the hard drives. This was in the day of removable hard drive platters, and now none of them worked. There were many, many more problems, we were fixing calibrations for months, even after things were generally running again. The hydraulic motion system never really was the same -- it was always a little rough after that event, even in 'calm air'.

The flight simulators were down completely for 2 weeks, which caused 2 aircraft squadrons to delay deployment because of pilot qualifications requiring actual flight time. Figure 4000 hours of high-performance military aircraft flight time, with according wear and tear, 2-4 weeks delay in deploying two aircraft carrier battle groups, and the ensuing ripple effect on the plans of the rest of the Navy.

Remember those helicopters that broke down during the hostage rescue in Iran, back in April of 1980? From the USS Nimitz? The Nimitz was at the end of it's deployment -- it's replacement was delayed for some reason...

Sorry for the length, I'll adjust to nominal value next time.
(danalan Pretty good, for an amateur., Sat 27 Oct 2007, 21:40, 1 reply)

But surely
if a supply is rated at 15±0.25V, setting it to 'exactly' 15V is within tolerance, so everything should work perfectly if it's been designed to work at that voltage.

Or have I misunderstood something?
( K2k6 has a proper job these days, Mon 29 Oct 2007, 8:41, closed)