Power conversionBench electronicsTest and identify
Schottky diode
Also called SS34, MBR, output rectifier.
A low-drop diode used as the output rectifier in older supplies and as a polarity guard. Useful when marked. The drop is lower than a 1N4007, which is the point, and the leakage is higher.
If you are new to this category
These parts change wall power into the lower voltage a device uses. A sealed supply with a label is the safer kind. An open board from a lamp can still be connected to the wall on the side that looks like low voltage. Isolated means the output is not electrically connected to the wall. If you are not sure, treat the output as live.
Read the label out loud: volts, amps, and the polarity symbol. Then measure. A number you remember from a similar brick is not a measurement.
Left: a brick. The label is your spec, and the plastic is the safety barrier. Right: a board taken out of a lamp or a charger. Unless you have checked that the output is isolated from the prongs, do not let it touch a project you will handle while it is plugged in.
| What to look for | Usual figure |
|---|---|
| Drop | About 0.2–0.5 V at modest current |
| Common marks | SS14, SS34, 1N5819, MBR series. Read yours. |
Volts are electrical pressure, amps are how much current is flowing, and ohms are how hard the part resists that flow. A higher voltage than the part was built for is how salvage parts die on the bench. If a cell in the table says “read the stamp”, that stamp is the whole specification.
What people actually use it for
- Polarity protection
- A buck catch diode, if the voltage and current ratings actually cover it
Leave this one when
Unmarked SOD package. Not worth the board damage.
Buying a new one is the better idea when
A labeled Schottky. The part costs less than the time.
How to tell if this one still works
Diode test. Lower drop than a standard silicon diode, open reverse.
Tools you will want: Meter.
Words on this page
Short meanings, so the rest of the entry is readable if you are not already doing this every weekend.
- polarity
- Which side is plus and which is minus. Reversed polarity ruins a lot of electronics. The symbol on a power brick is the map.
- rectifier
- A set of diodes that turns alternating current (the wall, which reverses) into one-direction current. The output is still bumpy until a capacitor smooths it.
- series
- Connected in a chain. Cells in series add their voltages. LEDs in series all go dark if one of them opens.
Where people actually find it
0 notes, most useful first. “Leave it” means the part is in that machine and you should not take it: it is dangerous, worn out, or only useful if you already know that exact repair.
| From | Call | How many | How often | Where it sits |
|---|