2017-06-01 How To Disable 5V Regulator?

I’ve been getting PC boards that have all the chips operating at 5 volts, but the input voltage has to be between 7 and 12 volts.  The board has a 5 volt regulator on the board, and often it is a surface mount chip.  But I have dozens of 5 VDC, 1/2 amp AC adapters, which would work just fine for powering these boards.  I can connect a 5 volt adapter to the input, but usually the 5 volt regulator chip has to drop 2 volts, leaving only 3 volts for the circuits.  I would have to connect the 5 volts to the output pin of the regulator chip, but I’m not sure if the regulator will allow this.  I would like to keep the chip, since I might use it later, and the chip might be difficult to obtain, and is not easy to remove or reinstall.

I should disconnect the regulator somehow.  I’ve considered several solutions, but I’m not sure which is the better, or even if they might work.  I’m looking for information, as it seems to me that I’m not the only one who has had this situation to deal with.

I thought one solution is to cut the trace at the output of the regulator chip.  Sometimes there are reasons that can’t be done.

Leave the regulator chip connected and hope it doesn’t eat up power.

Put a rectifier diode in series with the output.  This reduces the output voltage by up to a volt.  So to compensate, a diode would have to be put in series with the ground lead of the regulator.

Other thoughts.  One thought is to ask the board designers to add a point on the trace which is made to be cut open, and has a location on which to solder the 5 volt wire.  This only deals with future PC boards, and the designers may refuse to do it.

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