Resistor Trimmer Packages:

'A', 'B', 'C', 'D/E', 'F-L', 'M', 'N', 'O', 'P', 'R', 'S', 'T', 'V-Z'

Trimmer: A variable resistor. A trimmer is designed for less then frequent changes [occasional]~ a trim pot on a PCB to finalize a circuit resistance. A Trimmer may be Single Turn or Multi-turn, or surface mount or through-hole.
There are a number of common package styles, of which a number are shown below [Through-hole]. Note that the actual package style makes little difference in the circuit operation. Refer here for Surface Mount Trimmer Resistors. The actual style would be selected based on the layout of the printed wiring board, as each component is identical, except for the physical dimensions.

Square Body Trimmer
One of the most common body styles used for resistor trimmers. The actuator will either be top mount or side mount. With the leads or terminals in-line with each other or off-set.

Top mount actuator. Top mount trimmer resistors are used when the trimmer may be mount near the edge of the Printed Circuit Board [PCB], or when the board density is to great to allow a side adjustment.

Vertical Mount Square Body Trimmer Resistor Case Drawing
Trimmer, Off-set Leads, RJ26 Style

Side mount actuator [Rectangular body]. Side mount trimmers are normally used near the edge of a Printed Wiring Board [PWB]. A side mount trimmer allows for adjustments from the side of the PWB.

Horizontal Mount Square Body Trimmer Resistor Case Drawing
Trimmer, In-line Leads, RJ24 Style

Side mount actuator [Square body]. This is basically the same style trimmer as above, but with a lower profile. Of course the price of the reduced height profile is increased board area.

Side actuator Through-Hole Trimmer Resistor

Square Body Trimmer Resistor Case Drawing
Trimmer, Off-set Leads, RJ26 Style

Round Body Trimmer
Trimmers with a round body are the same as ones with a square body, only the body shape changes.

Board-Mount Round Body Trimmer Resistor Case Drawing
Trimmer, Rounded Trim-Pot

Rectangular Body Trimmer
This particular body style uses a lead-screw to change the resistance. This trimmer style also has the largest body of the trimmers shown on this page.

Rectangular Trimmer
Rectangular Through-hole Trimmer Resistor
Trimmer, Rectangular Trim-Pot

The trimmer in a rectangular package may also be purchased with wire leads instead of terminals [RJ12 style]. The larger body allows for a larger power dissipation [rated power]. Normal a panel mount version uses wire leads; the trimmer is secured to a panel, and then attached to the printed circuit card via wire leads, some distance from the panel the device is attached to. There is no relative size difference between the version shown and one with wired leads, the only difference being the leads used by the device.

Of course there are other styles of trimmer resistors, the above examples show some of the more common. However an example of a thumbwheel potentiometer is shown to the right. Yet another example of a board mount trimmer.

Thumbwheel Trimmer Resistor
RJ24 Style Trimmer

A topic seldom thought about is the style of shaft used by adjustable resistors. The most common shaft style which is also shown above, is the round shaft with the flat slotted head, but there are a number of possible other styles.

PC motherboard

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