On 5/11/2017 4:25 AM, Bob kb8tq wrote:
Ultimately it all came to no good. The energy conservation rules simply took over. Shutting down everything during off hours became the way a lot of outfits did things. Don’t turn off all
A couple of comments on this, probably no surprise to many time nuts. All or most HP instruments with 10811's keep the oven energized even if the instrument is turned "off". Many classic HP instruments used power transformers for power supplies. The secondaries were regulated by a combination of switches and linear regulators. The power module was mounted on the rear panel, along with the transformer, to help get rid of the heat without heating up the box too much. The dilemma was that you had to choose between four bad alternatives: 1. Put the power switch on the rear panel. This is inconvenient for the user, especially if the unit is racked. 2. Put the power switch on the front panel. This entails running wiring with all the safety approvals up to the front panel and back to the rear panel. I don't know of this ever being done at HP. 3. Have a button on the front panel that actuates a long plastic shaft the goes to the real switch at the back. Works, but quite a hassle. 4. What was usually done: leave the power transformer primary connected all the time and switch the secondaries. The HP transformer shop would often scrimp on the amount of iron in the transformer, which would increase the core loss. Their idea of good engineering practice was to allow the loss to heat the transformer up 10's of degrees. Note that core loss is independent of how much power you are drawing from the secondaries, if any. So in the overall scheme of things, the 10811 is small potatoes. Once it is warmed up, it doesn't draw much power. Rick N6RK _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.