I noticed that 3435A and 3466A DVMs, plus the 5316A counter, and presumably other models, are set up such that AC power is *always* applied to the transformer - the power switch only controls DC power. Therefore, my 3466A has been "on" (sort of) for several years without my knowledge.
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Why?
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I believe the reasons are:
- Some counters and such have crystal ovens that are intended to stay on.
- In the 3466A and 3435A, the reason is because of the battery option, so that the battery will charge with the switch Off. Note that in these units, an entire DC regulator circuit is alive at all times.
- My 5316A counter does not have an oven, but there is an Option for a 'better' time base with an oven, so I assume that's the reason.
- Another, perhaps less likely, reason could be to avoid the need to run 120VAC wiring from the back to the front of the cabinet, past sensitive analog circuits.
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Anyway, you *may* not want to leave some of these units plugged in when not in use, given the old components and such.?
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Pete
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saipan59 (Pete)