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Is it OK to connect the minus from a DC Power supply, 15v 4A (switched) to a metal chassi as ground? No electronics will be connected to the chassi.

The jacks that I have found seems to be made of metal, which in my eyes looks like the ”minus” will end up in the chassis.

  1. Is that ok?
  2. Does the minus act as ground through the power supply?
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  • \$\begingroup\$ What do you mean with "power jack"? Input or output? If it's an AC-to-DC power supply then it's quite common to connect the input ground (earth) directly to the chassis. \$\endgroup\$ – Rohat Kılıç Jul 24 '18 at 19:42
  • \$\begingroup\$ Input, female. The jack in the radio that welcomes the ac-to-dc power adapter plug. \$\endgroup\$ – Robert Pettersson Jul 24 '18 at 19:46
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    \$\begingroup\$ Technically it's impossible to answer this from the information provided. You're hinting at a grounded chassis "negative ground" setup, which is indeed very common. But other situations exist - ones where the supply is isolated from the chassis, and also ones (certain older automobiles, ongoing telecom installations) where ground is positive. \$\endgroup\$ – Chris Stratton Jul 24 '18 at 19:52
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    \$\begingroup\$ Ok sorry for that. I have this old radio from the 60s. It is a wooden box with the backplate in metal. I will not use any of the electronics inside, just keep it for the weight, and put a Raspberry Pi together with a JustBoom amp hat and connect it to the speakers. These are all isolated from the back metal plate and the rest of the old components. To power the pi, I will use an AC to DC power supply, 15v 4A. And I will drill a hole in the back and attach a dc Female jack. 5.5, 2.1mm. \$\endgroup\$ – Robert Pettersson Jul 24 '18 at 20:02
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    \$\begingroup\$ I will not use any of the electronics inside .... why are you asking about powering a radio then? .... i think that you need to rewrite your question and ask about powering an RPi ..... actually, your question makes no sense at all \$\endgroup\$ – jsotola Jul 25 '18 at 0:52
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If you have a socket similar to the shown below, you can see two tabs and metal ring. One of the tab is connected to the center pin (usually +), the other is connected to a small sleeve/tab inside (usually -). The plug albo makes a contact with the body of the socket (also usually -). The standard way is to connect the tabs to + and - on the PCB and let the body ring make contact with the chassis.

enter image description here

https://media.rs-online.com/t_large/F0487842-01.jpg

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Given that the backplate is not going to be connected to any of the active circuitry there will be no problem caused by connecting it to the supply negative.

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