43F82R

The Ohmite 43F82R is a wirewound power resistor from the Ohmicone® 40 series, delivering 82 ohms resistance at ±1% tolerance with 3W continuous power dissipation capability. This axial through-hole component measures 0.220" diameter by 0.594" length (5.60mm x 15.10mm), providing a compact footprint for power management circuits requiring precision resistance values in moderate power applications.

Wirewound construction provides inherent advantages in thermal stability and power handling compared to film-based alternatives. The 43F82R exhibits a temperature coefficient of ±20ppm/°C, maintaining resistance accuracy across operating temperature ranges commonly encountered in industrial control systems, automotive electronics, and power supply regulation circuits. The tight 1% tolerance reduces the need for circuit calibration or component selection during production, streamlining manufacturing processes for voltage divider networks, current sensing applications, and load simulation testing.

The 3W power rating supports operation in circuits where continuous current flow generates significant heat dissipation. Axial lead configuration facilitates traditional PCB mounting or point-to-point wiring in chassis-mounted assemblies. The two-termination design integrates directly into circuits requiring fixed resistance elements for motor control, LED driver current limiting, or pulse width modulation filtering stages.

Wirewound resistors excel in applications demanding low noise characteristics and stable performance under sustained load conditions. The 43F82R's construction minimizes voltage coefficient effects, making it suitable for measurement circuits, analog signal conditioning, and reference voltage generation where resistance linearity impacts system accuracy. The bulk packaging format addresses volume production requirements in contract manufacturing and repair depot operations.

This component serves power distribution systems, industrial automation equipment, and test instrumentation where the 82 ohm value provides impedance matching or current limiting functions. The Ohmicone® 40 series maintains active production status, supporting long-term availability for established designs. Equivalent alternatives include ALSR0382R00FE12 ALSR0382R00FE12 Vishay Dale RES 82 OHM 3W 1% AXIAL 68595 , 43F82RE 43F82RE Ohmite RES 82 OHM 1% 3W AXIAL 35653 , and RS02B82R00FS70 RS02B82R00FS70 Vishay Dale RES 82 OHM 3W 1% WW AXIAL 74619 for second-source qualification or supply chain redundancy planning.

When a specific wirewound resistor becomes unavailable due to supply chain constraints, end-of-life announcements, or lead time issues, engineers and procurement teams need to identify functionally equivalent alternatives that maintain circuit performance without requiring board redesign. The Ohmite 43F82R, an 82-ohm 1% tolerance 3W axial wirewound resistor from the Ohmicone 40 series, commonly appears in power supply feedback networks, current sensing applications, and precision load circuits where thermal stability and low temperature coefficient matter.

Direct replacements for this component include the Vishay Dale ALSR0382R00FE12 ALSR0382R00FE12 Vishay Dale RES 82 OHM 3W 1% AXIAL 68595 , Ohmite's own 43F82RE 43F82RE Ohmite RES 82 OHM 1% 3W AXIAL 35653 variant, and KOA Speer's RS02B82R00FS70 RS02B82R00FS70 Vishay Dale RES 82 OHM 3W 1% WW AXIAL 74619 . These alternatives share the core electrical specifications—82-ohm resistance, ±1% tolerance, 3W power rating—while introducing variations in physical dimensions, terminal configurations, or thermal characteristics that affect drop-in compatibility.

43F82R (1)

Understanding the Original Component Profile

The 43F82R employs wirewound construction wound on a ceramic core, providing inherent advantages in pulse handling and thermal mass compared to metal film or thick film technologies. Its ±20ppm/°C temperature coefficient ensures resistance drift remains within 0.16 ohms across a 100°C temperature swing, maintaining feedback accuracy in regulated power supplies or measurement circuits.

The axial lead format with 0.220-inch diameter and 0.594-inch body length dictates PCB footprint requirements. Standard through-hole mounting with 0.6-inch lead spacing accommodates most legacy board layouts, though the body diameter constrains component density in tightly packed assemblies. The 3W continuous power rating at 25°C ambient derate linearly to zero at the maximum operating temperature, typically 275°C for ceramic-core wirewound types, though Ohmite does not specify this parameter in standard documentation.

Wirewound construction introduces inductive reactance, typically 0.5 to 2 microhenries for this form factor, which becomes significant above 100 kHz. Applications switching at these frequencies—such as SMPS snubbers or high-speed current sensing—require verification that parasitic inductance does not introduce phase shift or resonance with circuit capacitance.

Vishay Dale ALSR0382R00FE12 Cross-Reference Analysis

The ALSR03 series from Vishay Dale targets industrial and automotive applications requiring AEC-Q200 qualification. This component maintains identical electrical specifications: 82 ohms ±1%, 3W power dissipation, and ±20ppm/°C tempco. The wirewound element uses similar ceramic substrate technology, ensuring comparable pulse withstand and thermal cycling performance.

Physical dimensions differ slightly—the ALSR03 measures 0.236 inches in diameter versus 0.220 inches for the 43F82R, an increase of 0.016 inches. This 7% diameter expansion requires verification of adjacent component clearances, particularly in dense layouts where vertical spacing approaches minimum design rules. Body length remains within 0.020 inches of the original, maintaining lead bend geometry for automated insertion equipment.

The ALSR03 specifies a maximum operating temperature of 275°C and provides a detailed derating curve: full 3W dissipation up to 25°C, linear derating to 0W at 275°C. This translates to 12mW/°C derating factor, allowing 2.1W dissipation at 100°C ambient. In contrast, the 43F82R datasheet provides typical derating without explicit maximum temperature, though ceramic wirewound construction suggests similar limits.

Terminal plating on the ALSR03 uses tin-lead solder coating, facilitating wave soldering and manual rework. The 43F82R employs tin plating, compatible with both leaded and lead-free processes. For RoHS-compliant assemblies, this difference requires process qualification to ensure reliable solder joint formation under lead-free reflow profiles, where peak temperatures reach 260°C versus 240°C for tin-lead.

Ohmite 43F82RE Internal Variant Comparison

The 43F82RE 43F82RE Ohmite RES 82 OHM 1% 3W AXIAL 35653 represents Ohmite's updated version within the same Ohmicone 40 family, differing primarily in terminal finish and packaging options. Electrical parameters remain unchanged: 82 ohms, ±1% tolerance, 3W rating, ±20ppm/°C tempco. Physical dimensions match exactly, ensuring mechanical interchangeability without board modification.

The "E" suffix typically denotes an extended temperature range or enhanced environmental rating in Ohmite's nomenclature, though specific documentation for the 43F82RE 43F82RE Ohmite RES 82 OHM 1% 3W AXIAL 35653 does not clarify additional qualifications beyond the standard 43F82R. Procurement teams should verify with Ohmite whether this variant includes improved moisture resistance, extended shelf life, or alternate lead forming compatible with automated assembly.

This option provides the most straightforward replacement path when the original 43F82R faces availability constraints. Manufacturing consistency within the same product family minimizes parametric variation across production lots, reducing qualification testing requirements. Applications sensitive to batch-to-batch resistance tolerance, such as precision voltage dividers or calibration circuits, benefit from single-source consistency.

KOA Speer RS02B82R00FS70 Alternative Evaluation

KOA Speer's RS02B series addresses similar industrial power applications with 82-ohm resistance, ±1% tolerance, and 2W continuous power rating at 70°C ambient. The reduced power rating—2W versus 3W—represents the primary functional difference requiring circuit-level analysis before substitution.

In applications where actual power dissipation remains below 1.5W, this derating does not constrain operation. For example, a current sensing resistor carrying 150mA continuous dissipates 1.85 watts, operating at 62% of the 43F82R's capacity but 93% of the RS02B's rating. Thermal rise calculations using the component's thermal resistance (typically 40-50°C/W for axial wirewound resistors) determine whether the RS02B maintains acceptable operating temperature under maximum load conditions.

Physical dimensions differ substantially: the RS02B measures 0.177 inches in diameter and 0.433 inches in length, approximately 20% smaller in diameter and 27% shorter than the 43F82R. This size reduction affects thermal mass—less ceramic material results in faster thermal response but higher peak temperatures during transient loading. Applications with pulsed power profiles, such as inrush limiting or switching transient damping, require pulse energy calculations to verify the RS02B's thermal time constant accommodates peak power without exceeding maximum temperature.

The RS02B specifies ±50ppm/°C temperature coefficient, 2.5 times higher than the 43F82R's ±20ppm/°C. Over a 100°C operating range, this translates to 0.41-ohm resistance drift versus 0.16 ohms for the original component. Precision circuits maintaining better than 1% accuracy across temperature, such as RTD signal conditioning or instrumentation amplifier gain setting, may exceed error budgets with this substitution.

Comparative Performance Summary

The following comparison consolidates electrical, thermal, and physical differences across all alternatives:

Electrical Characteristics:

• All candidates maintain 82-ohm nominal resistance with ±1% initial tolerance. The 43F82RE 43F82RE Ohmite RES 82 OHM 1% 3W AXIAL 35653 and ALSR03 preserve the ±20ppm/°C temperature coefficient, while the RS02B's ±50ppm/°C specification introduces additional temperature-dependent error. Power ratings span 2W to 3W, with the RS02B requiring derating analysis for applications exceeding 1.5W continuous dissipation.

Thermal Performance:

• The ALSR03 provides explicit 275°C maximum operating temperature with defined derating curves. The 43F82RE 43F82RE Ohmite RES 82 OHM 1% 3W AXIAL 35653 inherits the original 43F82R's thermal specifications. The RS02B's smaller thermal mass results in faster temperature response, beneficial for surge protection applications but potentially limiting in continuous high-power circuits where thermal stability determines long-term reliability.

Physical Compatibility:

• The 43F82RE 43F82RE Ohmite RES 82 OHM 1% 3W AXIAL 35653 offers exact dimensional match, enabling drop-in replacement without board redesign. The ALSR03's 7% diameter increase requires clearance verification but maintains similar body length. The RS02B's 20% size reduction provides additional clearance but may affect heat dissipation in designs relying on radiant cooling from the resistor body.

Regulatory and Process Compatibility:

• The original 43F82R carries RoHS non-compliant status, limiting use in EU markets or consumer electronics. The ALSR03 and RS02B both meet RoHS requirements, though terminal plating differences affect soldering process qualification. The 43F82RE 43F82RE Ohmite RES 82 OHM 1% 3W AXIAL 35653 's compliance status requires verification based on current manufacturing lot specifications.

Validation Methodology for Thermal and Electrical Performance

Using the Vishay Dale ALSR0382R00FE12 ALSR0382R00FE12 Vishay Dale RES 82 OHM 3W 1% AXIAL 68595 as the reference replacement, practical verification follows a structured approach addressing thermal derating, electrical accuracy, and mounting compatibility.

Thermal Derating Verification:

• Install the ALSR03 in the target circuit and measure body temperature using a type-K thermocouple affixed to the resistor center with thermally conductive adhesive. Apply maximum rated current and monitor temperature stabilization, typically achieved within 10-15 minutes for 3W wirewound resistors in free air. Compare measured temperature against the manufacturer's derating curve: at 3W dissipation, body temperature should not exceed 280°C (275°C maximum plus 5°C measurement tolerance). For convection-cooled installations, verify ambient temperature measurement location—readings should be taken 1cm upstream of the resistor to avoid influence from self-heating.

Resistance Drift Measurement:

• After initial thermal stabilization at maximum power, reduce current to zero and log resistance recovery using a four-wire ohmmeter at 30-second intervals. The resistance should return to within ±0.1% of the cold resistance value within 5 minutes, indicating proper thermal design and absence of solder joint degradation. Temperature-dependent resistance measurements require a temperature-controlled chamber: measure resistance at 25°C, 75°C, 125°C, and 175°C, plotting the temperature coefficient. The measured slope should remain within ±25ppm/°C to account for measurement uncertainty and component tolerance.

Parasitic Inductance Assessment:

• For switching applications above 50 kHz, characterize the resistor's impedance versus frequency using a vector network analyzer with test fixtures providing short, consistent ground return paths. Sweep from 10 kHz to 1 MHz and extract series inductance from the impedance phase angle. Wirewound resistors in this form factor typically exhibit 0.8 to 1.5 microhenries. Compare the ALSR03's inductance against the original 43F82R; differences exceeding 20% may affect snubber networks or current sense bandwidth. High-speed current sensing applications requiring sub-microsecond response time should verify that inductive reactance remains below 10% of the DC resistance at the maximum operating frequency.

Mechanical Fit Verification:

• Assemble production PCBs with the ALSR03 using normal manufacturing processes—automated insertion followed by wave soldering or selective soldering. Inspect for lead interference with adjacent components, particularly connectors or tall capacitors within 5mm of the resistor body. Use calipers to verify the installed body diameter clears surrounding components by at least 1mm, ensuring adequate voltage clearance and thermal isolation. Perform thermal cycle testing per IPC-9701: -40°C to +125°C, 500 cycles, with resistance measured before and after cycling. Resistance drift exceeding ±0.5% indicates solder joint stress or thermal expansion mismatch requiring lead forming adjustment.

Selection Framework Based on Application Requirements

High-precision analog circuits maintaining better than 0.5% accuracy across temperature favor the Ohmite 43F82RE 43F82RE Ohmite RES 82 OHM 1% 3W AXIAL 35653 or Vishay ALSR0382R00FE12 ALSR0382R00FE12 Vishay Dale RES 82 OHM 3W 1% AXIAL 68595 , both preserving the ±20ppm/°C specification. These applications include precision voltage references, instrumentation amplifier gain networks, and calibrated measurement shunts where temperature-induced error directly affects system accuracy.

Power circuits dissipating near the 3W maximum rating, such as inrush current limiters or precharge resistors in high-voltage DC systems, require full power capability. The 43F82RE 43F82RE Ohmite RES 82 OHM 1% 3W AXIAL 35653 and ALSR03 both support 3W continuous operation, while the RS02B's 2W rating necessitates either circuit redesign to reduce power dissipation or selection of a higher power variant from the RS03B series.

RoHS-compliant manufacturing environments exclude the original 43F82R and require verification of the 43F82RE 43F82RE Ohmite RES 82 OHM 1% 3W AXIAL 35653 's current compliance status. The ALSR03 carries clear RoHS marking and provides AEC-Q200 qualification for automotive applications. The RS02B similarly meets RoHS requirements while offering cost advantages in commercial-grade applications without automotive qualification requirements.

Space-constrained designs benefit from the RS02B's reduced footprint, provided power dissipation remains within the 2W rating and the elevated temperature coefficient does not compromise circuit accuracy. Conversely, designs with generous component spacing and thermal management benefit from larger body sizes that distribute heat more effectively and reduce surface temperature.

For immediate replacement with minimal requalification testing, the Ohmite 43F82RE 43F82RE Ohmite RES 82 OHM 1% 3W AXIAL 35653 provides the most direct path, maintaining complete electrical and mechanical compatibility. When the 43F82RE 43F82RE Ohmite RES 82 OHM 1% 3W AXIAL 35653 faces similar availability constraints or procurement seeks dual-source options, the Vishay ALSR03 offers comparable performance with broader distribution and automotive-grade qualification.