Hi I am hoping someone could help me with an old 1992 GM vehicle PC board. I have sketched out the circuit as best I can and attached photo of the original transistor. I cannot find any info on this transistor online. Looking for advice on a readily-available replacement item in the TO-92 type package. The relay that it switches has a coil resistance of 73ohms, so should need approx 0.2amps to operate it at 12vdc.
Any advice much appreciated.

 

2N2222

 

Awesome thankyou very much.

 

PN2222A is in TO-92.

 

Ah thank you. That will be easier to fit on the pcb.

 

2N2222

or BC337 if you want a European part

 

OK yes I see I can buy that one here locally.
Out of curiosity, does anyone have any old spec info on the original transistor.? I think it is a 3248 or N202.
Wondered if it had some high current capability or unusual characteristics...?
Thank you.

 

Wondered if it had some high current capability or unusual characteristics...?

Is it a darlington? To drive a relay at 200mA from 1mA base current is asking a lot for a single transistor.
Try a MPSA14
https://www.onsemi.com/pdf/datasheet/mpsa13-d.pdf

 

I'm not sure since I could not find any reference to it on the 'net. I have to admit that the original part has worked since 1992, but then I see on a forum for the vehicle, that this particular failure is not uncommon... I was thinking a modern substitute may be more durable or even wondered if I could fit a device with a bit more capacity to avoid another failure.

 

I'm not sure since I could not find any reference to it on the 'net.

My first thought was that it could be a 2N3248, but that device is in TO-18.

I was thinking a modern substitute may be more durable or even wondered if I could fit a device with a bit more capacity to avoid another failure.

As long as the substitute will handle at least 200mA, reliability shouldn't be an issue because the transistor is being used as a switch - either on or off.

If you go with BC337, be aware that the pinout is reversed from PN2222A and the device in question.

 

OK good thanks. I will go with the 2222A.

 

I will go with the 2222A

Note that there are 3 2222A variants. 2N2222A, PN2222A, and P2N2222A. The first is in TO-18. The other 2 are in TO-92 but have different (reversed) pinouts.

A 2N2222A in TO-92 is technically mislabeled.

 

Great thanks. I will see what my local store has available today. They claim that they have P2N2222A. I can rotate the transistor when I solder it on, to allow for reversed pinout if necessary I guess.

 

OK good thanks. I will go with the 2222A.

It won't have enough gain.
To get Vsat<0.4 at Ic=150mA needs Ib =15mA, and you have Ib=1mA

 

OK this is where my very limited knowledge runs out. Maybe that original device did have some special characteristics.? Would that explain why it is difficult to find references to it? It shows in that photograph that I posted at the start of this thread..

 

There are two of those transistors next to each other. Maybe it's configured as a darlington.
If the TS can confirm the connections.

 

No it’s just the one transistor. There are actually three identical circuits on the pcb which run three relays.

 

Are the other two transistors defective as well. Do any of those relay circuits work?

 

No they are working fine still. I used those circuits to figure out how it works and to conclude that this one transistor is faulty.

 

No they are working fine still. I used those circuits to figure out how it works and to conclude that this one transistor is faulty.

Are you certain the base resistor is 5k?