2SD2385 + 2SB1556 Transistors

Will wonders never cease ? This place actually has a datasheet ! (they failed me so much I no longer bother, but at the end it said "PDF" so I got it)

http://www.datasheetcatalog.org/datasheet/toshiba/3250.pdf

If you really cannot get them you can make Darlingtons, but I don't recommend it. However when you look at the internal diagram you see the the EB junction on a meter is not going to read like a Darlington because of the 100 ihm resistor across the EB junction of the output. You would only see the drop of the driver EB junction. Depending on your meter it might read 0.100 higher, but will not read 1.2 volts as you might expect.

You are not ordering a million of these things, if the right part is a bit more expensive it is worth it. Like someone said B & D, but then I don't know where you are. If not in the US, dealing internationally can be a PITA.

J

 

[Phil Allison]

"fruittool"

To me, the pictures look genuine,

** But you are an utter idiot.




..... Phil

 

[Phil Allison]

<jurb6006@gmail.com>

http://www.datasheetcatalog.org/datasheet/toshiba/3250.pdf


** Shame the schem in the above omits the reverse diode across the C and E
terminals.

Easiest way to pick a power darlington with an ohm meter.


..... Phil

 

Actually it might not have one, there is no law.

With two resistors, a DVM and a 12 volt supply you can measure the hfe quite easily.

That 100 ohm resistor is much more important, otherwise the Icex of the first transistor at the very least will always be applied to the base of the second transistor. The Ice leakage numbers for the whole device would look like germanium.

J

 

[Phil Allison]

<jurb6006@gmail.com>

Actually it might not have one, there is no law.

** Every darlington power transistor made has a reverse diode from C to E -
it is part if the structure of the chip.

All power mosfets have a similar diode.

With two resistors, a DVM and a 12 volt supply you can measure the hfe
quite easily.

** But you gotta be real quick or the device will cook.

That 100 ohm resistor is much more important, otherwise the Icex of the
first transistor at the very least will always be applied to the base of
the second transistor. The Ice leakage numbers for the whole device would
look like germanium.

** Hogwash.

The 100ohm resistor is there to improve the switch off speed of the power
transistor plus increase the breakdown voltage a little.

Leakage current in the driver transistor is only a few microamps, at most, a
current level the output device can barely amplify at all.


..... Phil

 

[Sofa Slug]

On 10/26/2012 7:21 AM, chuck wrote:

On Thu, 25 Oct 2012 20:06:24 +0000, fruittool
fruittool.acf52c8@diybanter.com> wrote:


I've just been done on ebay. Both output transistors on a Kenwood A-97
amplifier had blown. Ordered the pair from ebay, installed them,
working, great. Turned it off to put it back together and noticed the
heatsink was really hot on the repaired side. I found that the base
voltage on both transistors was low. Swapped both transistors from the
good side to the repaired side and its now fine. Put the new ones in the
good side the and now the good side has got hot and all the voltages
have dropped the same as they did when they were on the repaired side.

Does anyone know where i can get a genuine pair of these transistors at
a reasonable price?


http://www.bdent.com/ only carries genuine semiconductor
manufacturer's lines. Chuck

http://www.pacparts.com/part.cfm