7.3Ω 200W Adjustable Resistor – Vintage Industrial Power

This unit is a 7.3Ω 200W Adjustable Resistor of the Dividohm type (wirewound with exposed section). Unlike fixed resistors, this model features a longitudinal strip where the resistive alloy winding is exposed, allowing the metal slider (clamp) to be positioned at any point to obtain intermediate resistance values. It can operate as a voltage divider or a high-power rheostat.

Key Features of the 7.3Ω 200W Adjustable Resistor:

• High-Durability Construction: Wirewound on a high thermal conductivity ceramic core to prevent hot spots.

• Vitreous Enamel Coating: The rough gray finish is not just aesthetic; it protects the resistive wire against oxidation and moisture, ensuring long service life in industrial environments.

• Clamp Adjustment: Includes a stainless steel sliding contact that ensures a firm and stable electrical connection.

• Item Condition: Although it shows surface patina consistent with its vintage age, the filament has been tested to ensure continuity and accuracy within its original tolerance range.

Technical Specifications – 7.3Ω 200W Adjustable Resistor:

• Nominal Resistance: 7.3 Ω (Ohms)

• Maximum Power Rating: 200W (Watts)

• Resistor Type: Wirewound

• Adjustment Method: Adjustable Slider (Semi-Fixed)

• Body Material: Ceramic and Vitreous Enamel

• Approx. Dimensions: (Based on 200W standard): ~260 mm length í— 30 mm diameter

• Mounting: Ends designed for central bolt mounting or side clamp installation.

History & Manufacturer

Based on its morphology, the “7.3” marking, and the characteristic gray coating, this component corresponds to the classic product line of Ohmite Manufacturing Company (or competitors from the golden era such as Ward Leonard or Clarostat).

Applications & Target Audience – 7.3Ω 200W Adjustable Resistor

Who is this product ideal for?

• Engineers & Technicians: Ideal for load banks used in power supply testing.

• Ham Radio Restorers: Critical replacement component for vacuum tube transmitters.

• Education: Ideal for laboratory experiments on Ohm’s Law and heat dissipation.

• Industry: Suitable for DC motor speed control or inrush current limiting.

(FAQ)

Q: Can I use it to vary motor speed?
A: Yes, as long as the motor’s power consumption does not exceed 200W and the 0–7.3 ohm range is sufficient to achieve the required voltage drop.

Q: Why does the surface look rough and uneven?
A: This is characteristic of vintage vitreous enamel coating. Its purpose is thermal and protective, and it does not affect the electrical performance of the internal resistive element.

Q: Does it come with mounting hardware?
A: The listing includes the resistor and the adjustable clamp shown in the photos. Additional chassis mounting hardware is not included.