Overview
The LCR-T4 is a pocket component analyzer: clamp almost any two- or three-legged part into its ZIF socket, press the button, and the screen tells you what the part is, which pin is which, and its measured values. Resistors, capacitors (with ESR), inductors, diodes, NPN/PNP transistors, MOSFETs, JFETs, and small thyristors — identified automatically, no range dials, no guessing pinouts from datasheets.
For electronics repair and prototyping it earns its bench space fast: sorting mystery-drawer transistors, checking salvaged capacitors' health via ESR, verifying a resistor before it goes in circuit, and identifying unlabeled parts. It runs from a 9V battery and needs nothing else — there is nothing to wire, only parts to test.
At a Glance
Identifies
R, C, L, diodes, transistors
Capacitance
25 pF - 100,000 µF
Extras
ESR, hFE, Vf, pinout ID
Specifications
| Parameter |
Value |
| Resistance Range |
0.1 Ω to 50 MΩ |
| Capacitance Range |
25 pF to 100,000 µF (with ESR on electrolytics) |
| Inductance Range |
0.01 mH to 20 H |
| Transistors |
NPN/PNP: hFE, base-emitter voltage, pinout; Darlingtons detected |
| FETs |
N/P-channel MOSFETs (gate threshold, gate capacitance) and JFETs |
| Diodes |
Single and dual diodes, forward voltage, protection diodes in transistors |
| Also Detects |
Small thyristors/triacs, resistor pairs, capacitor+resistor combos |
| Socket |
3-terminal ZIF, zones 1-2-3 (any part orientation) |
| Operation |
Single button: test / menu; auto power-off |
| Power |
9V 6F22 battery (or DC input on some boards) |
How to Use
1. Insert the part — orientation doesn't matter
Lift the ZIF lever, place the component's legs into any of the three numbered zones (two-leg parts use any two zones), and lock the lever. The tester figures out what's connected where — that's its magic. For SMD parts, hold them against the pads beside the socket if your board has them.
2. Press the button and read
One press runs the full analysis. The screen draws the part symbol with pin numbers matching the socket zones, plus values: resistance; capacitance with ESR and Vloss; inductance with DC resistance; transistor type, pinout (B/C/E or G/D/S), hFE, and junction voltages; diode forward voltage.
3. Calibrate once, then occasionally
Short all three zones together with a wire or leg clipping, then run a test — the tester enters self-calibration (follow the prompt; it may ask you to remove the short and, on some firmware, insert a >100 nF capacitor). Calibrate when new, after battery swaps, and whenever tiny resistances read oddly.
Warning: Discharge capacitors before testing — a charged cap (especially a big electrolytic or anything that touched mains) can destroy the tester instantly. Short the cap through a resistor (100 Ω - 1 kΩ) for a few seconds first. Never test parts in a powered or in-circuit board.
Note: In-circuit readings aren't meaningful anyway — surrounding components parallel the part under test. Lift at least one leg for truthful numbers.
Tip: A weak 9V battery causes drifting, nonsensical readings long before the tester dies outright. When values wander, swap the battery before doubting your parts.
Frequently Asked Questions
It shows "No, unknown, or damaged part." What does that mean?
Either poor socket contact (re-seat, clean oxidized legs), a part outside supported ranges (e.g. caps under 25 pF), a genuinely dead component, or a part type it can't analyze (ICs, crystals, big triacs). Try a known-good part to rule out the tester.
What is ESR and why do I care?
Equivalent Series Resistance — the internal resistance of a capacitor. Aging electrolytics fail by ESR rising long before capacitance drops, which is why power supplies "mysteriously" die. Low single-digit ohms is healthy for most electrolytics; tens of ohms on a big cap means replace it.
Can it test capacitors smaller than 25 pF or Zener diodes?
Below 25 pF is under its floor — measure small caps with an LC meter. Zeners read as ordinary diodes unless their breakdown is below the tester's ~4.5V test voltage; higher-voltage Zeners need a dedicated Zener tester (the T7 class adds this).
Why does my MOSFET read differently between tests?
Gate charge lingers between tests and skews threshold readings. Briefly short all three MOSFET legs together with your fingers or a wire before re-testing, and it will settle. Static-sensitive parts appreciate a grounded wrist strap, too.
The screen is blank or garbled after inserting a battery. Is it dead?
Check battery polarity and voltage first (a fresh 6F22 reads ~9.5V). Many boards also have a contrast trimmer near the LCD — a slight turn restores a "blank" display. Bare-board versions deserve a case or standoffs to prevent bench shorts.
How accurate is it compared to a real LCR meter?
Think percent-level, not lab-grade: excellent for identification, sorting, and go/no-go health checks; not a substitute for a calibrated bridge when precision matters. For hobby repair, it's usually all the accuracy you need.
