Major U.S. distributors list the Bourns 3386F-1-101LF as an active, through-hole cermet single-turn trimmer (100 Ω, 0.5 W), a common choice for precision trimming in consumer and industrial electronics. This article unpacks the part for design engineers, buyers, and bench technicians: what to read from the datasheet, how to wire and footprint it, test and verify performance, and where to source authenticated inventory. The term datasheet appears below where key extraction guidance is provided.
Point: The 3386F-1-101LF is a single-turn cermet trimmer in a compact 3/8" square, top-adjust package intended for through-hole mounting. Evidence: Distributor catalogs and manufacturer part summaries identify it as a 100 Ω, ±10% tolerance, 0.5 W rated, top-adjust device commonly used for voltage trim, bias settings, and calibration tasks. Explanation: Cermet composition gives low contact noise and stable resistance over time compared with carbon film types; single-turn action provides fast adjustment and "infinite" resolution across the travel range, making the device well-suited for production calibration points, prototype tuning, and small-signal circuits where power dissipation is low and mechanical robustness is required.
| Parameter | Typical / Absolute Value |
|---|---|
| Resistance | 100 Ω ±10% |
| Power rating | 0.5 W (operating, derate as recommended) |
| Voltage rating | 300 V (maximum) |
| Temperature coefficient | ±100 ppm/°C |
| Dimensions | 9.52 × 9.52 mm (3/8" square) |
| Turns | 1 (single-turn) |
| Mounting | Through-hole; wave-solder compatible per manufacturer notes |
Point: Use the table as a one-row summary to place on procurement or BOM documents. Evidence: The values above represent common datasheet fields (resistance, power, voltage, TCR, dimensions). Explanation: For final design or procurement, always extract the exact numeric tolerances, derating guidance, and mounting notes from the official datasheet and distributor product pages to prevent mismatch between quote and production part.
Point: Differentiate absolute maximums from recommended operating limits when documenting the part. Evidence: Typical datasheets list absolute ratings (e.g., max voltage, max power) plus suggested operating ranges and derating curves. Explanation: Absolute ratings show conditions that must never be exceeded (e.g., 300 V max, 0.5 W peak power), while recommended operating conditions provide safe working points and derating rules (power versus ambient temperature). Present both sets on the design sheet: highlight absolute limits in red, and recommended conditions (such as 50–70% of rated power for continuous use) in the design notes to avoid premature failure under thermal stress or continuous loading.
Point: Key parameters directly affect circuit accuracy and stability. Evidence: Parameters like wiper-to-terminal resistance, end-to-end tolerance, temperature coefficient, mechanical life, and contact resistance/noise are specified in the datasheet. Explanation: Wiper resistance and contact noise influence low-level signal performance and can introduce offset or jitter in high-gain stages; TCR (±100 ppm/°C) determines drift with temperature; mechanical life (tens of thousands of cycles typical for single-turn trimmers) dictates serviceability in adjustable interfaces. Explicitly call out these values in the component selection worksheet so designers can simulate drift and tolerance worst-cases during tolerance analysis and Monte Carlo runs.
Point: Vendors’ data should be validated with simple bench tests and vendor documentation. Evidence: Distributor stock pages and manufacturer notes provide lot and traceability metadata that procurement should capture. Explanation: Recommended verification steps include measuring resistance sweep across travel to confirm full-range behavior and end-to-end tolerance, conducting power dissipation tests at representative currents while monitoring temperature rise, and performing thermal-drift tests across the expected operating range. Request lot traceability and date codes from suppliers and run sample testing on incoming lots (sample size per AQL guidance) before approving for production use.
| Pin | Function | Expected behavior |
|---|---|---|
| Terminal 1 | End terminal A | Continuity to terminal 3 through resistive element; varies with wiper position |
| Wiper | Adjustable contact | Variable tap; measured between wiper and each end terminal |
| Terminal 3 | End terminal B | Complementary end of resistive element |
Point: Standard 3-pin mapping supports use as variable resistor or potentiometer. Evidence: Top-adjust orientation determines which mechanical location corresponds to the wiper; manufacturer drawings indicate the wiper position for top-adjust variants. Explanation: For top-adjust devices, the center pin is typically the wiper when the adjustment screw is on top and the pins face toward the PCB. Confirm orientation against the footprint drawing when placing the part to ensure wiring diagrams (variable resistor vs. voltage divider) match the intended circuit behavior.
Point: Proper pad and drill sizing, plus clearance and mechanical anchoring, prevent stress and soldering defects. Evidence: Manufacturer mechanical drawings list pad dimensions and recommended drill sizes for through-hole pins. Explanation: Use recommended drill sizes with a plated through-hole annular ring per your PCB house standards, provide an adequate keepout to avoid copper pours near the body, and include mechanical anchor points for boards subject to vibration. Common mistakes include undersized pads that complicate wave soldering and placing nearby surface traces under the plastic body where reflow/wave-induced heating may cause thermomechanical stress.
Point: Three common wiring patterns cover the majority of use-cases: variable resistor, voltage divider, and feedback element. Evidence: Circuit designers typically use a single-turn trimmer as a series variable resistor to set current, as a potentiometer in a divider for reference trimming, or as a fine-tune element in op-amp feedback. Explanation: For initial calibration, set the wiper near mid-range for divider trims to allow ± adjustments, while for bias-setting use a position that keeps dissipation well below the 0.5 W rating. Document the initial mechanical position on the assembly drawing to speed calibration during test and production.
Point: A brief, repeatable pre-assembly checklist reduces field failures. Evidence: Standard QC practice combines visual and electrical checks from distributor and manufacturer acceptance criteria. Explanation: Recommended steps are visual inspection for physical defects or contamination, continuity checks to verify correct pin-to-pin mapping, resistance verification at minimum and maximum travel positions, and an insulation/voltage-withstand check if the application exposes the part to high potentials. Record batch and date codes to link any anomalies to supplier lots.
Point: Safe and stable adjustment preserves trim integrity and repeatability. Evidence: Manufacturer torque limits and recommended adjustment tools (insulated, nonmagnetic) guide safe procedures. Explanation: Use insulated plastic or ceramic adjustment tools to avoid introducing shorts; respect manufacturer torque and travel limits to avoid mechanical damage; adopt a consistent adjustment sequence—coarse set with power off, then final trim under operating conditions to account for thermal and load effects. If long-term stability is required, lock the adjustment with approved adhesives or mechanical retainers and document the final setting.
Point: Recognize common failure signatures and escalation steps. Evidence: Field reports and lab diagnostics typically show wiper noise, intermittent contact, and overheating as frequent issues. Explanation: If noisy output or intermittent resistance is observed, perform a mechanical exercise of the wiper to detect wear, then validate contact resistance under low-voltage conditions. Overheating suggests power dissipation miscalculation—measure current and compute power; if close to or exceeding 0.5 W, select a higher-power part or redistribute dissipation. Replace parts that show unstable contact resistance or mechanical wear beyond specified life cycles.
Point: Follow manufacturer guidance for through-hole soldering and cleaning to avoid damage. Evidence: Datasheet remarks and distributor notes indicate wave-solder compatibility for many through-hole trimmers, with caveats on maximum immersion time and temperature. Explanation: Use recommended wave profiles, limit immersion time to the manufacturer’s maximum, avoid high-temperature reflow exposure for through-hole-only parts, and select cleaning solvents compatible with internal materials. When in doubt, consult the sealed-to-wash statement on the datasheet and perform a trial assembly to validate solder fillet quality and absence of flux entrapment under the body.
Point: Humidity, thermal cycling, and mechanical shock influence long-term reliability. Evidence: Temperature coefficient and mechanical life ratings in the datasheet quantify sensitivity. Explanation: Store and handle devices in moisture-controlled environments if the datasheet flags moisture sensitivity; design for thermal cycling by allowing free-board clearance and avoiding rigid potting that transmits stress to solder joints. For harsh environments consider conformal coating or potting where permissible, testing coated samples for expected mechanical life and drift before committing to a full-scale protective strategy.
Point: Define pass/fail criteria and sampling plans tied to datasheet specs. Evidence: Production QA practices rely on sample inspection against resistance tolerance, mechanical integrity, and functional tests. Explanation: Suggested incoming inspection checks include visual identification, resistance at nominal wiper positions, and torque/adjustment validation for a 1% sample per lot; use an AQL-based sampling plan for larger lots. Establish pass/fail criteria referencing datasheet tolerances (e.g., resistance ±10%, contact resistance thresholds) and record results alongside supplier lot codes for traceability.
Point: Prefer established authorized distributors to minimize supply and authenticity risk. Evidence: Major U.S. distributors stock the part and provide stock status, pricing, and metadata useful to procurement. Explanation: Typical sources include national electronics distributors; when ordering, confirm the manufacturer part number and suffixes (for example, LF indicates lead-free processing), request date codes and lot traceability, check MOQ and lead times, and monitor price trends for spikes that may indicate supply constraints. Keep a verified supplier list and compare quoted metadata against manufacturer packaging and marking expectations during incoming inspection.
Point: Gray-market sources can introduce counterfeit or mis-marked parts. Evidence: Procurement best practices flag unverified dropshippers, odd labeling, or unexpectedly low pricing as red flags. Explanation: To mitigate risk, require certificates of conformance, request photographs of reel/packaging and date codes, and, for critical applications, insist on direct shipment from authorized distributors or the manufacturer. Inspect packaging and markings against known-good samples and perform sample electrical testing when switching suppliers or using unfamiliar channels.
Point: Evaluate form-fit-function equivalents rather than only direct replacements. Evidence: Similar single-turn cermet trimmers exist with comparable resistance and power ratings, but mechanical dimensions or adjustment orientation can differ. Explanation: When substituting, compare resistance value, tolerance, power rating, TCR, mechanical dimensions (pad spacing and body height), and adjust orientation. Consider slightly higher power or tighter TCR if reliability margins are needed. Use cross-reference searches by resistance, power, and package style to find alternatives and validate footprint compatibility before committing to a BOM change.
Concise recap: the 3386F-1-101LF is a 100 Ω, 0.5 W cermet single-turn top-adjust trimmer in a 3/8" square through-hole package; designers must extract the datasheet’s absolute ratings, recommended operating limits, and mechanical drawings for accurate footprint and thermal derating. Follow the practical verification steps—resistance sweep, power dissipation checks, and batch traceability—to validate vendor claims, and source from authorized distributors while checking lot codes and LF/lead-free suffixes. Download the official datasheet from Bourns and validate parts from authorized U.S. distributors before production.
The 3386F-1-101LF is a 100 Ω, ±10% single-turn cermet trimmer in a top-adjust, through-hole 3/8" square package. Its datasheet contains electrical ratings, mechanical drawings, and environmental limits; procurement and design teams should obtain the official datasheet from the manufacturer to extract exact tolerances, derating guidance, and footprint dimensions before layout or purchase.
Wiring as a voltage divider uses the two end terminals as the resistor endpoints and the wiper as the adjustable tap. Start calibration near mid-travel to allow symmetric adjustment range, verify the wiper center pin mapping against the mechanical orientation on the PCB, and perform final trimming in-circuit under operating conditions to account for thermal and loading effects.
For batch verification, perform visual inspection, confirm resistance at minimum, mid and maximum travel, run a resistance sweep to detect discontinuities, and conduct a power dissipation test under representative current while monitoring temperature rise. Record date codes and supplier lot IDs, and compare results to datasheet tolerances; reject lots showing out-of-spec drift or intermittent contact.