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I am building a power supply using LM78×× voltage regulators. The circuit works as expected with no load but when I connect the circuit to external connectors, LM7812 on circuit starts getting very hot.

My inference: The metal in the connector is acting as ground and forming a short thereby making current maximum and LM7812 hot.

•Is my inference correct ?

•If yes , how can this be solved ?Image of connector used

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    \$\begingroup\$ It also could be that once you put a significant load on the circuit, a large amount of power is dissipated in the regulator. What is the input voltage, output voltage, and load current? \$\endgroup\$
    – crj11
    Mar 1, 2019 at 14:15
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    \$\begingroup\$ A hunk of metal would not "act as ground" - it could create a connection if it touches two conductors, but it is not anything itself. It's not really clear what you are asking here as you include no details of the circuit, assembly, input, or output. \$\endgroup\$
    – Chris Stratton
    Mar 1, 2019 at 14:27
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    \$\begingroup\$ Do you have the hole in the sheetmetal sized correctly such that the inner projection on one of those insulators passes through it when the metal is clamped between the two insulators? \$\endgroup\$
    – Phil G
    Mar 1, 2019 at 14:29
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    \$\begingroup\$ You need to add a schematic so we can see how everything is connected. If possible, a photo of your setup alongside it would be a good idea. Without a schematic, all we can do is guess \$\endgroup\$
    – MCG
    Mar 1, 2019 at 14:29
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    \$\begingroup\$ If the connector would make a short to ground, you wouldn't have any results with no load. But The circuit works as expected with no load, so it's likely not short circuiting. @crj11 's comment is most likely the case. \$\endgroup\$
    – Huisman
    Mar 1, 2019 at 14:34

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The 78xx is a linear regulator, which means among other things, that its power dissipation is directly proportional to the load current. A heatsink is required to keep its temperature within an acceptable range.

How much current does your load draw?

Also, @Phil G raised an important point: if you're mounting your banana jack to a metal panel, the panel must go between the two plastic insulators, with a clearance hole that's large enough to acommodate the positioning shoulder(s) on them.

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  • \$\begingroup\$ Got it! I drilled holes only for the metal contact of connector ignoring insulation between it and the metal body. I am going to fix that. Thank you all. \$\endgroup\$
    – Rutuparn_Pawar
    Mar 2, 2019 at 5:55

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