2N2222 Transistor orientation?

[Che_Guitarra]

I've been fiddling around with a Vox V847 wah pedal - all I have left to do is install the 2N2222 transistors that were suggested for the job.  They're metal can style parts and i've i've not used them before, and i'm not sure how to orient them on my PCB.  Can anyone advise me?

 

[joaquins]

Well, you need to know how are the pins on the board, if you have any more data of it would help. In other case you could trace it, it's a pretty simple design so no problem with that.

Here are some useful links, a partial datasheet http://circuit-diagram.hqew.net/2N2222-datasheet_8491.html
and a img from wikipedia http://upload.wikimedia.org/wikipedia/commons/5/5e/2N2222A_and_schema.jpg
Both seems to be the same thing. I'd test it with a multimeter for hfs and when it shows the max will have the pins printed on the DMM, this old stuff sometimes were manufactured with a different pinout than the standard part.

JS

 

[Che_Guitarra]

Here's a schematic of the circuit.

My guess is that the pointer on the transistor cap indicates the emitter leg and should line up with the pointer on the transistor symbol in the schematic?  Unfortunately no way to test for HFS... I do have a DMM just for measuring transistor values, but after three days of looking for the bloody thing i've got no idea where I put it  :-[

 

[joaquins]

which DMM? brand and model, to help. there should be a place with 'e', 'b' and 'c' letters, various of them, and PNP and NPN designation, typically 8 hole socket.

I do know the schematics of that, I don't know your specific board.I'd trace them with the adjacent components to know which pin is which in the board...

JS

 

[Che_Guitarra]

I've got a few DMMs - one of which has the HFS function.  Unfortunately I can't find it to tell you what brand/model it is... it's just an el-cheapo unit.

No need to help me with board layout - I understand what is going where in relation to the schematic.  What I want to know is the orientation/pinout of this particular transistor - the emitter leg, from the base leg, from the collector leg.  I'm unfamiliar with metal cap style transistors - i've only ever used the moulded plastic style.

 

[ruairioflaherty]

What I want to know is the orientation/pinout of this particular transistor - the emitter leg, from the base leg, from the collector leg.  I'm unfamiliar with metal cap style transistors - i've only ever used the moulded plastic style.

The pinout can vary by manufacturer, you'll need to find the datasheet for your specific transistors.

 

[joaquins]

Well, here are a couple of DMM examples

For this one the transistor goes in the round blue socket, NPN for your 2n2222, which pin on which hole is the thing to determine, just 4 ways to place it an any of those would damage the transistor.
For this other in the rectangular black socket. You may start trying as the picture of wiki I posted, if it reads something over 100 it's fine and that's the way.

Ah, hfs was a typo, hFE is the right way to write it.

JS

 

[PRR]

Diode checker.

You see the arrow on the transistor symbol, for emitter-base diode. The collector-base is another diode. Collector-emitter does not act as a diode. So poking your diode checker at the transistor, all six ways, you will find two diodes. You know the tab points at the Emitter. So the collector should be clear.

Or find the data-sheet. For that '2222, or for any metal TO-92 can (they all de same).

If you still need a clue: base is in center.

Now for that PCB....

A properly docced kit should tell you. (Especially since plastic-blob transistors are NOT all the same pin-out.) However, you can sort it. Q1 has a 100r to E, a 1K5 to B, and a 22K to C. Q2 has similarly distict resistors on each leg. You even have those numbers printed-on. (Albeit hidden under the bodies.) (And if they could print resistor values, why not E B and C?)

 

[moamps]

The tab on the metal transistor's (BJT) chassis shows always the emitter.
So, find where are emitter resistors R4 and R10 connected on the board to the transistors pins, and you will find the transistor's orientation. 
And there is an error in labeling on the board, the Q1 and 2 are reversed, IMO.