The **GMA-7-R** is a specific model of a fast-acting, glass tube fuse commonly used in electronic circuits to protect sensitive components from overcurrent conditions. It is part of the GMA series produced by manufacturers like **Eaton (Bussmann Series)**. --- ### 1. Technical Specifications The "GMA-7-R" nomenclature identifies the specific electronic characteristics of the part: | Parameter | Specification | |:---|:---| | **Part Number** | GMA-7-R | | **Current Rating** | 7 Amperes (7A) | | **Voltage Rating** | 125V AC (Standard) / 250V AC | | **Response Characteristic** | Fast-Acting (Fast Blow) | | **Body Material** | Glass Tube | | **Physical Dimensions** | 5mm x 20mm (standard small cartridge) | | **Termination Style** | Ferrule (Clip-in) | | **RoHS Compliant** | Yes (indicated by the "-R" suffix) | --- ### 2. Key Component Features * **Fast-Acting Response:** Unlike "Slow-Blow" (Time-Delay) fuses, the GMA-7-R is designed to open almost instantly when the current exceeds its 7A rating. This is critical for protecting semiconductor-based circuits that can be destroyed by even brief surges. * **The "-R" Suffix:** In electronic part numbering, the "-R" denotes **RoHS Compliance**. This means the part is manufactured without hazardous substances like lead, mercury, or cadmium, making it compliant with international environmental standards. * **Glass Construction:** The transparent glass body allows for easy visual inspection. If the fuse is "blown," you can usually see a broken wire or a dark smudge inside the tube. * **Interrupting Rating:** This fuse typically has an interrupting rating of 200A at 125VAC, meaning it can safely break a short circuit current of up to 200 Amps without the glass tube shattering. --- ### 3. Common Applications The GMA-7-R is a "subminiature" fuse used in a variety of consumer and industrial electronics: 1. **Consumer Electronics:** Power supplies for desktop computers, monitors, and audio equipment. 2. **Instrumentation:** Multimeters, oscilloscopes, and laboratory power units. 3. **Appliances:** Control boards for microwave ovens or small kitchen appliances. 4. **Chargers:** Battery charging stations for power tools. ### 4. Comparison: GMA vs. GMC/GMD When replacing this part, it is vital to distinguish between the series types: | Series | Type | Application | |:---|:---|:---| | **GMA** | **Fast-Acting** | Protecting sensitive ICs and transistors. | | **GMC** | Medium Time-Delay | General purpose protection. | | **GMD** | Time-Delay (Slow-Blow) | Used where high "inrush" currents (like motors) occur. | --- **Warning:** Always replace a GMA-7-R with a fuse of the exact same current (7A) and voltage (125V/250V) rating. Replacing a fast-acting fuse with a slow-blow fuse could result in permanent damage to your device.