SMD code 78A
Marking codes are not standardised, and the same code is reused by unrelated makers for unrelated parts. Below is every part in our tables printed with it, and any printed with a code that is easy to misread as it, from the manufacturers' own marking tables and published code lists.
78A on a chip resistor
634 Ω
634 Ω resistor, 1%
EIA-96 precision code: 78 selects 6.34 from the E96 series and A multiplies by 100. These are 1% parts.
Check it with a meter
Lift one end and measure across it. A good one reads 634 Ω within 1%. Measuring it in circuit reads the parallel combination of everything around it, which is almost always lower, never higher: well above 634 Ω on the board is a fault. Open, or well above 634 Ω, means it has failed: burnt, cracked or corroded. That does not change what to fit: the marking still says 634 Ω. 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-23-5, USP-6C, SOD-123F), 78A is a part code instead. Those parts are listed below.
19 parts are printed 78A
Not sure which one you have?
Answer up to 4 quick questions and these 19 parts are ranked, with a meter test that settles it. It works on a dead part too.
APW7178ADFNDC-DC converter, AnpecDC-DC converterDFNNot recordedAnpec
- What it is
- DC-DC converter
- Maker
- Anpec
- Package
- DFN
- Pins
- Not recorded
- Details
- 1.5MHz, 1A Synchronous Buck Regulator
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Integrated circuit.
GSF2TVS78ASOD-123FTVS diode, 2 pins, Good-ArkTVS diodeSOD-123F2 pinsGood-Ark
- What it is
- TVS diode
- Maker
- Good-Ark
- Package
- SOD-123F
- Pins
- 2
- Details
- TVS diode, 200 W
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
SFL2J78A-CSOD-123FTVS diode, 2 pins, SeCoSTVS diodeSOD-123F2 pinsSeCoS
- What it is
- TVS diode
- Maker
- SeCoS
- Package
- SOD-123F
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
SM4F78ASOD-123FTVS diode, 2 pins, YFWTVS diodeSOD-123F2 pinsYFW
- What it is
- TVS diode
- Maker
- YFW
- Package
- SOD-123F
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
SMB15J78A-HFSMBTVS diode, 2 pins, ComchipTVS diodeSMB2 pinsComchip
- What it is
- TVS diode
- Maker
- Comchip
- Package
- SMB
- Pins
- 2
- Details
- 78 V 1500 W unidirectional TVS diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
SMF78ASOD-123FTVS diode, 2 pins, Good-ArkTVS diodeSOD-123F2 pinsGood-Ark
- What it is
- TVS diode
- Maker
- Good-Ark
- Package
- SOD-123F
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
1SMC78ASMCTVS diode, 2 pins, EIC SemiconductorTVS diodeSMC2 pinsEIC Semiconductor
- What it is
- TVS diode
- Maker
- EIC Semiconductor
- Package
- SMC
- Pins
- 2
- Details
- TVS: 78V, 11.4A, 1500W(1ms)
- Source
- Published code list
Is it dead? The meter test is below: TVS or ESD protection diode.
MMF78ASOD-123FTVS diode, 2 pins, Shanghai SemitechTVS diodeSOD-123F2 pinsShanghai Semitech
- What it is
- TVS diode
- Maker
- Shanghai Semitech
- Package
- SOD-123F
- Pins
- 2
- Details
- Transient voltage supressor: Vrwm=78V, Vbr=86.7..99.7V, Ipp=1.4A, 200W(1ms)
- Source
- Published code list
Is it dead? The meter test is below: TVS or ESD protection diode.
P4SMAFJ78ASMAFTVS diode, 2 pins, Dongguan You Feng Wei ElectronicsTVS diodeSMAF2 pinsDongguan You Feng Wei Electronics
- What it is
- TVS diode
- Maker
- Dongguan You Feng Wei Electronics
- Package
- SMAF
- Pins
- 2
- Details
- TVS diode, unidirectional
- Source
- Published code list
Is it dead? The meter test is below: TVS or ESD protection diode.
P4SMAJ78ASMATVS diode, 2 pins, YeashinTVS diodeSMA2 pinsYeashin
- What it is
- TVS diode
- Maker
- Yeashin
- Package
- SMA
- Pins
- 2
- Details
- TVS: 78V, 2.2A, 400W (1ms)
- Source
- Published code list
Is it dead? The meter test is below: TVS or ESD protection diode.
P4SMFJ78ASOD-123FTVS diode, 2 pins, YeashinTVS diodeSOD-123F2 pinsYeashin
- What it is
- TVS diode
- Maker
- Yeashin
- Package
- SOD-123F
- Pins
- 2
- Details
- Transient voltage supressor: Vrwm=78V, Ipp=2.2A, 400W (1ms)
- Source
- Published code list
Is it dead? The meter test is below: TVS or ESD protection diode.
SMAJ78ASMATVS diode, 2 pins, SynSemiTVS diodeSMA2 pinsSynSemi
- What it is
- TVS diode
- Maker
- SynSemi
- Package
- SMA
- Pins
- 2
- Source
- Published code list
Is it dead? The meter test is below: TVS or ESD protection diode.
SMBG78ASMBGTVS diode, 2 pins, Microsemi Integrated Products DivisionTVS diodeSMBG2 pinsMicrosemi Integrated Products Division
- What it is
- TVS diode
- Maker
- Microsemi Integrated Products Division
- Package
- SMBG
- Pins
- 2
- Details
- 600 W TVS diode, unidirectional
- Source
- Published code list
Is it dead? The meter test is below: TVS or ESD protection diode.
2 more parts have no package on record
SM15KWE78ATVS diode, ProTek DevicesTVS diodeNot recordedNot recordedProTek Devices
- What it is
- TVS diode
- Maker
- ProTek Devices
- Package
- Not recorded
- Pins
- Not recorded
- Details
- 15 Kilowatt TVS Components
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
3PMT78ATVS diode, Microsemi Integrated Products DivisionTVS diodeNot recordedNot recordedMicrosemi Integrated Products Division
- What it is
- TVS diode
- Maker
- Microsemi Integrated Products Division
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Transient voltage supressor: Vvm=78V, Vbr=86.7V, Vcl=126V, 11.4A, 1500W (1ms)
- Source
- Published code list
Is it dead? The meter test is below: TVS or ESD protection diode.
Is it dead? One meter test per kind
Parts of the same kind are tested the same way, so each test is here once. Each part above points to its own.
Integrated circuit
Voltage with the board powered; ohms from each pin to ground with it off.
Working, it reads
Supply pin at its voltage and the output doing what the datasheet says. Readings between pins depend on the part.
Dead, it reads
- A pin near 0 Ω to ground or to the supply pin where an identical part does not read that: failed short.
- Supply present, output stuck: failed, or its load has.
- On the board:
- A pin shorted to ground on the board can be anything on that net. Lift the pin to be sure.
- Compare:
- The surest reference is the same IC on a working board, measured pin by pin.
- Watch for:
- Its protection diodes can read like junctions between pins, even like a transistor. That proves nothing either way.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
TVS or ESD protection diode
Diode range, from the protected line to ground, part lifted if you can.
Working, it reads
A one-way part reads about 0.6 to 0.8 V forward and open in reverse. A two-way part reads open both ways. Arrays with several lines read as the datasheet's diagram draws them.
Dead, it reads
- From the line to ground, the same reading both ways, near 0 V with a continuous beep: shorted.
- A reading both ways on a one-way part: leaky.
- A one-way part open both ways: failed open.
- On the board
- , a line reading shorted to ground can be this part or anything else on that line. Lift it: if the short goes with it, it has failed.
- Compare:
- The same part on the next line or connector pin is the healthy reading to compare with.
- Watch for:
- A two-way part reads open both ways when it is good, exactly like one that has failed open. The meter cannot tell them apart; an identical part on the next line can.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Printed with a code easy to misread as 78A
One character differs, and it is one that is easy to confuse under a lamp. Each code has a page of its own.
Did you find your part?
Open this in the search to correct a character or try another package.