How can I check the quality of my BC550 Transistors?

[matta]

Hey Guys,

I managed to buy a couple BC550?s this weekend from 2 more Green Pre?s and a
few other projects I will start working on. Unfortunately I can?t tell who
the manufacturer is, is just has CBC550 on the transistor, but that code
brings nothing up on All Data or in Google and the supplier doesn?t know the
manufacturer.. Go figure. All I know is that the max voltage is 50V and it has
a 100 Milli amp rating. Do you think these will be good enough to use? Is
there any test I can do to check the quality? Neeno mention checking the HFE?
How do you do this?

Thanks

Matt

 

[Bo Hansen]

Matta,

I think Philips make one of the best BC-550/560 transistors.
The transistor is markt with PH, and use BC-550-C if you whant highest HfE (good for front end transistor in preamps)

I`m sure even Motorola, National, SGS also make good BC-550, but don`t buy transistor that not have a brand name.

--Bo

 

[bcarso]

Might be Central Semiconductor. But I don't know anything about their quality.

For beta, put a megohm from base to collector, emitter to ground. Put an ammeter in series with the +5V d.c. supply or something close and measure the current. The base current will be about 4.4uA. Divide your measured collector current by that to get beta at that particular current. The number should be at least a few hundred.

 

[clintrubber]

To know what's happening, nothing beats the method Brad described.

(For not really needed added accuracy you could measure Vbe & the resistor-value).

For convenience, nothing beats plugging the device into one of those DMMs with a transistor-socket. A supermaket recently sold DMMs with socket/beta-function for I thought 3 Euro's :roll: So I got me a few, always handy to see various non-critical voltages, currents etc at the same time.

Regards,

Peter

 

[matta]

Hey Guys,

Thanks for all the feedback, for the easy, and harder tests, they will come in handy. I'm still new at this, so got to learn from the more experienced, and I thank you all for your willingness to teach.

Cheers

Matt

 

[CJ]

You could put it in an audio circuit and listen to it. I am finding out the hard way that this is probably a good idea for noise screening.
Don't ask me for a circuit for this, maybe somebody else has one.

 

[bcarso]

That's a good idea CJ. It would be nice to have two simple preamps of complementary designs, one with a socket for the NPN input device and the other for PNPs. The ear is a pretty good spectrum analyzer, especially when it comes to differentiating among different kinds of noise, like popcorn, white, pink...

Of course you want to make sure the device under test is passing a signal too.

Reminds me of the advice given to someone when he asked how a cheap powered speaker's sound could be improved. The answer came: "Turn it OFF!"