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1.2 kΩ resistor. 1 printed with a similar-looking code.
122 on a chip resistor
1.2 kΩ resistor, 5%
12 followed by 2 zeros. Three digits is normally the 5% series. The same marking also reads as 1.2 nF on a capacitor or 1.2 mH on an inductor, and nothing in the code says which; the body of the part does.
Lift one end and measure across it. A good one reads 1.2 kΩ within 5%. Measuring it in circuit reads the parallel combination of everything around it, which is almost always lower, never higher: well above 1.2 kΩ on the board is a fault. Open, or well above 1.2 kΩ, means it has failed: burnt, cracked or corroded. That does not change what to fit: the marking still says 1.2 kΩ. A burnt resistor usually means the part it feeds drew too much, so find that before fitting a new one.
On a transistor or diode body (SOT-23), 122 is a part code instead. Those parts are listed below.
This part is printed with a character that is easy to misread as what you typed. The odd one out is marked on each.
Printed L22 on the part. Easy to misread as 122. Check that character with a loupe before you order anything.
Diode range, part lifted or one leg off the pad. Red probe on the anode.
Working, it reads
About 0.5 to 0.8 V anode to cathode, and open the other way. Small switching diodes read about 0.6 to 0.7 V; large rectifiers can read a little lower.
Dead, it reads
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
For a marking with its end worn or burnt off. Each one shows its full printed code.
Zener diode, all Panjit.
Printed 1Z2V5B. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.
Working, it reads
About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.
Dead, it reads
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Printed 1Z20B. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.
Working, it reads
About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.
Dead, it reads
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Printed 1Z22B. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.
Working, it reads
About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.
Dead, it reads
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Printed 1Z24B. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.
Working, it reads
About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.
Dead, it reads
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Printed 1Z25B. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.
Working, it reads
About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.
Dead, it reads
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Printed 1Z27B. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.
Working, it reads
About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.
Dead, it reads
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Printed 1Z28B. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.
Working, it reads
About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.
Dead, it reads
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.