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I'm looking at a vintage wire recorder that won't even turn on. Examining it, the power leads (both of them) go through separate mercury switches and on to the main transformer, etc.

The switch vials are positioned so that the mercury will act as a "tilt switch" in case the thing (which is an entire piece of furniture) is falling over forwards.

Why have this, what function do they provide other than this peculiar tilt switch? Is it not better to take them out and dispose of them safely?

It turned out that the switches were thoroughly cold soldered and those connections had gotten very loose. I took the opportunity to re-route the incoming leads to the destination of the outgoing leads, thus preparing to remove the mercury components ... if that's all right to do.

collage of device

schematic

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  • \$\begingroup\$ This player may have been crated for more than 1 type of cabinet. I could see a record player that folds out like a Murphy Bed. Such a player would certainly not want to be spinning while in the vertical position. \$\endgroup\$
    – st2000
    Feb 24 at 19:23
  • \$\begingroup\$ @st2000, I see what you mean, but assuming that is not the case (and that I dont hold an EE degree) might those switches have an additional reason for being there? I know they're not "conditioning the input power", but ... perhaps something else along those lines? \$\endgroup\$
    – noughtnaut
    Feb 24 at 19:37
  • \$\begingroup\$ The most common reason for using a mercury switch is to protect the contacts from oxidation. \$\endgroup\$
    – Grace
    Feb 24 at 20:05
  • \$\begingroup\$ I have not head of any use (conditioning input power) for mercury switches. And now I see other have answered w/my same comment. And they are getting up voted. Which means many people are agreeing. I think you've found your answer. \$\endgroup\$
    – st2000
    Feb 24 at 23:25

2 Answers 2

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They're exactly as they appear, tilt switches so that the unit will only power up when in the correct orientation. If you don't need that functionality you can bypass them.

As for the problem of them containing mercury, there's no real need to remove them. They've been in there a long time without any problem, taking them out and trying to 'dispose of them safely' could increase the risk of breaking them. You generally only need to remove them if you are discarding the device. If you do want to remove them be careful and have a container to put them in with some protective padding ready, transfer them straight into that, seal it up and then you can dispose of it with someone that specializes in hazardous substance disposal.

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Why have this? I have seen tilt-down record players, where a cabinet panel tilts down revealing a record player mounted on the back

so this feature is probably intended to facilitate the use of this mechanism in that application. enter image description here

image from pintrest. https://www.pinterest.nz/pin/62487513556911863/

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