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Parts List Entry for Potentiometer with Switch

Apr 3rd 2015, 18:53

WN8P

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
You have seen this for eons. The on/off-volume control for your radio. The power switch is attached to a potentiometer and both operated by the same shaft. On the schematic diagram these components are usually drawn separately, in the part of the schematic where the subcomponent is used, and they may even have separate reference designators, an R# and an S#. In the parts list (PL) there may two entries, one for the potentiometer (R#) and one for the switch (S#). Or you might see one item entry with both reference designators in the REF DES column. On the ASSY DWG (parts layout) you probably would see both ref des next to the component.

Here is the better way: The Class Designation Letter "A" stands for a separable ASSY, a printed circuit board assembly (PCBA) is an example. Whereas the Class Designation Letter "U" stands for an inseparable ASSY; that is why ICs use this class letter unless there is a more specific one, such as AR for amplifier (op amp) or VR for voltage regulator. This combo part would use the class letter U--anything potted, riveted, imbedded, or hermetically sealed uses the class letter U, including a PCB but not a vacuum tube as it has its own V class letter.

In the PL this part would be listed with its ref des U# (one item, one reference designator, one part number) and this is what would be on the ASSY DWG (parts layout). On the schematic diagram you would find U#R1 and U#S1 for the particular subpart.

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