1. Introduction
The Brother HD-390A+ is a high-precision analog multimeter designed for electricians, home maintenance, and general electrical testing. It offers a wide range of measurement capabilities including DC voltage, AC voltage, DC current, resistance, battery testing, transistor hFE, diode, decibel, and continuity checks. This manual provides essential information for safe and effective use of your multimeter.
2. Safety Information
- Always ensure the multimeter is set to the correct function and range before connecting to a circuit.
- Do not attempt to measure voltages or currents exceeding the specified maximum ratings of the device.
- Exercise extreme caution when working with live circuits. Always assume circuits are live until proven otherwise.
- Inspect test leads for any damage (e.g., cracked insulation, exposed metal) before each use. Replace damaged leads immediately.
- Replace batteries and fuses only with the specified types and ratings to maintain safety and performance.
- Do not operate the multimeter if it appears damaged or is not functioning properly.
3. Setup
3.1 Battery Installation
The HD-390A+ multimeter requires two AAA 1.5V batteries and one 9V battery for operation. Batteries are not included with the device.
- Locate the battery compartment on the back of the multimeter.
- Open the battery cover by pulling down and opening as indicated on the cover.
- Insert the two AAA 1.5V batteries and one 9V battery, ensuring correct polarity (+/-) as marked inside the compartment.
- Close the battery cover securely.
Visual reference for battery compartment:
Back view of the Brother HD-390A+ multimeter, highlighting the battery cover.
3.2 Connecting Test Leads
- Insert the black test lead into the 'COM' (Common) jack.
- For most measurements (voltage, resistance, low current), insert the red test lead into the 'VmAΩ+' jack.
- For high DC current measurements (up to 10A), insert the red test lead into the '+10A' jack.
Visual reference for test lead connection:
Front view of the multimeter with test leads connected to the appropriate jacks.
3.3 Zero Ohm Adjustment
Before measuring resistance, it is crucial to perform a Zero Ohm Adjustment to ensure accuracy.
- Set the rotary switch to any resistance (Ω) range.
- Short the red and black test leads together.
- Turn the 'Ω ADJ' knob (yellow knob) until the pointer reads exactly zero on the resistance scale. This compensates for internal battery voltage variations.
4. Operating Instructions
4.1 Overview of Controls
The multimeter features a central rotary switch to select the measurement function and range, an 'Ω ADJ' knob for resistance calibration, and input jacks for test leads.
Front view of the Brother HD-390A+ multimeter, illustrating the main controls and display.
4.2 Reading the Analog Scale
The analog display features multiple scales for different measurement types. Always refer to the scale corresponding to the selected function and range on the rotary switch.
4.3 Measurement Procedures
- Measuring DC Voltage (DCV):
- Set the rotary switch to the desired DCV range (0.1V, 2.5V, 10V, 50V, 250V, 1000V). Start with the highest range if the voltage is unknown.
- Connect the red test lead to the positive side of the circuit and the black test lead to the negative side.
- Read the value from the DCV scale.
- Measuring AC Voltage (ACV):
- Set the rotary switch to the desired ACV range (10V, 50V, 250V, 1000V). Start with the highest range if the voltage is unknown.
- Connect the test leads across the AC voltage source.
- Read the value from the ACV scale.
- Measuring DC Current (DCmA):
- IMPORTANT: Ensure the circuit is de-energized before connecting the multimeter in series.
- Set the rotary switch to the desired DCmA range (50uA, 2.5mA, 25mA, 250mA). For 10A, use the '+10A' jack and the 10A range.
- Break the circuit and connect the multimeter in series with the load.
- Re-energize the circuit and read the value from the DCmA scale.
- Measuring Resistance (Ω):
- IMPORTANT: Ensure the circuit is de-energized and the component is isolated before measuring resistance.
- Set the rotary switch to the desired Ω range (X1, X10, X100, X1K, X10K, X100K).
- Short the test leads and perform a Zero Ohm Adjustment using the 'Ω ADJ' knob (see Section 3.3).
- Connect the test leads across the component.
- Read the value from the Ω scale and multiply by the range multiplier.
- Battery Check (BATT):
- Set the rotary switch to the 1.5V or 9V BATT range.
- Connect the red test lead to the positive terminal of the battery and the black test lead to the negative terminal.
- Read the battery condition (GOOD, ?, BAD) from the BATT scale.
- Transistor hFE Check:
- Set the rotary switch to the hFE range.
- Insert the transistor leads into the appropriate NPN or PNP sockets.
- Read the hFE value.
- Diode Check:
- Set the rotary switch to the Diode Check range (via Test Leads).
- Connect the test leads across the diode.
- Observe the reading to determine forward voltage drop or open circuit.
- Decibel (dB) Measurement:
- Set the rotary switch to an ACV range.
- Read the dB value from the dB scale.
- Continuity Check:
- Set the rotary switch to the Rx1 range.
- If the resistance is less than approximately 200 Ohms, a beeper will sound.
4.4 Video Demonstration
Watch this video for a practical demonstration of the Brother HD-390A+ multimeter's basic functions, including resistance and voltage measurements.
Video demonstrating the operation of the Brother HD-390A+ Analog Multimeter.
5. Maintenance
5.1 Battery Replacement
When the pointer does not zero correctly during resistance measurement, or the battery check indicates low power, it's time to replace the batteries. Follow the steps outlined in Section 3.1, 'Battery Installation'.
5.2 Fuse Replacement
If the multimeter fails to measure current or shows an open circuit on a known good circuit, the fuse may be blown. The device is protected by Fuses 0.5A/250V and 10A/250V (for the 10A range). Fuse replacement should ideally be performed by qualified personnel. Always replace with fuses of the exact same type and rating.
5.3 Cleaning
Wipe the multimeter casing with a dry, soft cloth. Do not use abrasive cleaners, solvents, or immerse the device in water.
5.4 Storage
Store the multimeter in a cool, dry place, away from direct sunlight, extreme temperatures, and high humidity. Remove batteries if storing for extended periods to prevent leakage and damage.
6. Troubleshooting
- No Reading/No Pointer Movement:
- Check if the multimeter is turned ON (rotary switch not in OFF position).
- Ensure test leads are correctly inserted and not damaged.
- Verify battery charge; replace if necessary.
- Check for blown fuses, especially for current measurements.
- Ensure the rotary switch is set to the correct function and range.
- Incorrect Reading:
- Verify the correct range is selected for the measurement.
- Perform Zero Ohm Adjustment for resistance measurements.
- Ensure good, clean contact between test leads and the circuit/component.
- Check for external electrical interference.
- Buzzer Not Sounding (Continuity):
- Ensure the rotary switch is set to the Rx1 range.
- Confirm that the resistance of the circuit being tested is below approximately 200 Ohms.
7. Specifications
The following tables detail the technical specifications of the Brother HD-390A+ Analog Multimeter:
General Specifications
- Dimensions: 160mm * 105mm * 40mm
- Standard Environmental Conditions: 23°C ± 5°C, humidity <75% RH
- Working Environment Range: 0°C ~ 40°C, humidity <90% RH
- Power Supply: R03P, AAA, 1.5V x2pcs (for Ω, Buzzer, hFE, Diode testing); 6F22 NEDA1604 9V x 1pc (just for Ω(Rx10k) testing).
- Protection: Full protection.
Measurement Specifications
| Test Functions | Range | Accuracy | Remarks |
|---|---|---|---|
| DC V | 0-0.1-2.5-10-50-250 V -1000V | ±3% FSD. ±4% FSD. For 1000V | Input Impedance: 20KΩ/V Overload Protection: Max. 1000V AC/DC BUT 0.1V/2.5V/10V 250V Max. |
| AC V | 0-10-50-250V -1000V | ±4% FSD. ±5% FSD. For 1000V Band width: 40 ~ 10K Hz | Input Impedance: 9KΩ/V Overload Protection: Max. 1000V AC/DC But 10V/50V only 250V Max. |
| DC mA | 0-0.05-2.5-25-250 mA, 10A | ±3% FSD. ±4% FSD. For 10A | Drop Voltage: 250 mV Overload protected by Fuses 0.5A/250V & 10A/250V at 10A range Max. testing time |
| Test Functions | Range | Accuracy | Remarks |
|---|---|---|---|
| Ω | X 1: 0.2 ~ 2KΩ Midscale at 20Ω X 10: 2 ~ 20KΩ Midscale at 200Ω X 100: 20 ~ 200KΩ Midscale at 2000Ω X1K: 200 ~ 2MΩ Midscale at 20KΩ X10K: 2K ~ 20MΩ Midscale at 200KΩ X100K: 20K ~ 200MΩ Midscale at 2000KΩ | ±3% of ARC of Scale Length | Protected by the extra Thermal Resettable Fuse <250V AC/DC. Powered by AAA 1.5V x2pcs & block 9V battery x1pc. |
| Capacitance (uF) | 0.025-0.25-25uF(C2 50uA), 2000uF(C1) | ±3% FSD. Approximate Value | Use the Accessory Kit Use the R x 1K range |
| BATT Check | 0 ~ 1.5V: GOOD ? - BAD 0 ~ 9V: GOOD ? - BAD | ±5% of ARC of Scale Length | Load Current: 270mA for 1.5V 25mA for 9V Overload protected by Fuse & Oxide Varactor <250V (5s). |
| Transistor, LED hFE Check | hFE: 0-1000 via special hFe socket Check | Approximate Value | At Ω X 10 Range |
| Diode Check | via Test Leads | Approximate Value | At Ω X 10 Range |
| Decibel | -22 dB ~ + 62 dB (0dB=1mW at 600Ω) | Approximate Value | At ACV ranges |
| Continuity Check | •))) At Rx1 range | Beeper sounding <200 Ohm approx. | Protected by the Resettable Fuse & Oxide Varactor <250V (5s). |
8. User Tips
- Always start with a higher range when measuring an unknown value to prevent overloading the meter and ensure safety.
- For resistance measurements, ensure the component is isolated from the circuit to get an accurate reading.
- Keep the test leads organized and free from tangles to avoid damage and ensure quick setup.
- Consider purchasing a spare set of fuses and batteries to minimize downtime during critical tasks.
9. Warranty and Support
For warranty information, technical support, or service inquiries, please contact the original seller or manufacturer directly. Please retain your purchase receipt as proof of purchase for any warranty claims.
