Pulled two of these SOT-89, "BE" transistors out of a P.S. driver card. It was in a totem config. with an NPN transistor marked "DF". Both "BE" transistors tested bad.
So first off I am trying to find a replacement for the "BE" transistor. Next I am somewhat confused because when I try to find info on it. all of the transistors I find with the marking "BE" are said to be NPN. I don't believe this is true because when testing the drive signal at the base of the power supply fets I had a sloping falling edge on the drive signal, indicating a bad PNP drive transistor not pulling the signal down properly correct?
Also, when I try to cross the "DF" transistors I keep finding them listed as PNP. But they test good as NPN. And the rising edge of the drive signal is nice and straight vertical.
So I am a bit puzzled.
So first off I am trying to find a replacement for the "BE" transistor. Next I am somewhat confused because when I try to find info on it. all of the transistors I find with the marking "BE" are said to be NPN. I don't believe this is true because when testing the drive signal at the base of the power supply fets I had a sloping falling edge on the drive signal, indicating a bad PNP drive transistor not pulling the signal down properly correct?
Also, when I try to cross the "DF" transistors I keep finding them listed as PNP. But they test good as NPN. And the rising edge of the drive signal is nice and straight vertical.
So I am a bit puzzled.
Any info on a good place to try to look these things up to decode them? SMD codebook didn't seem to be any help.
It seems to depend where you are looking,
one thing to note when searching and finding the code, make sure to check that the package corresponds to the actual component,
let's say if the package for BE was a SOT23 it would have been a BAS70 schottkydiode instead..
DF - BFN21 300V/50mA PNP
BE - BCX55 60V/1A NPN
source for the codes above:
http://www.electroschematics.com/wp-content/uploads/2013/04/SMD-code-book.pdf
But if you look at the Rohm datasheet for the 2SB1260 it has marking "BE"
http://rohmfs.rohm.com/en/products/databook/datasheet/discrete/transistor/bipolar/2sb1260.pdf
Unfortunately the SMD codes are not unique hence it is easy to make mistakes...
one thing to note when searching and finding the code, make sure to check that the package corresponds to the actual component,
let's say if the package for BE was a SOT23 it would have been a BAS70 schottkydiode instead..
DF - BFN21 300V/50mA PNP
BE - BCX55 60V/1A NPN
source for the codes above:
http://www.electroschematics.com/wp-content/uploads/2013/04/SMD-code-book.pdf
But if you look at the Rohm datasheet for the 2SB1260 it has marking "BE"
http://rohmfs.rohm.com/en/products/databook/datasheet/discrete/transistor/bipolar/2sb1260.pdf
Unfortunately the SMD codes are not unique hence it is easy to make mistakes...
Last edited:
See those are what I was finding saying the BE was NPN and the DF was PNP. That's not correct though.
For smaller components, sometimes the package sizes are so close that you need dial/digital calipers to get the right one.
When finding similar (same package) transistors used in a drive circuit, they're often complementary. The datasheets often give the complementary part number. If the complement has the correct marking, it's a good chance that you have the right parts.
When finding similar (same package) transistors used in a drive circuit, they're often complementary. The datasheets often give the complementary part number. If the complement has the correct marking, it's a good chance that you have the right parts.
Marking smd
DF is listed on the site above and the datasheet gives its complement. Many times no one can find the original part and it takes someone experimenting with replacement parts to find a suitable replacement.
DF is listed on the site above and the datasheet gives its complement. Many times no one can find the original part and it takes someone experimenting with replacement parts to find a suitable replacement.
So I have the same part but which is correct? For an Amp for a car. Is it 2SB1260 which is 80 volts or the BCX55 which is 60 volts? Amplifier drives so much power you can't guess or blow the amp again. Thanks.
- Status
- Not open for further replies.