Please take a look at the 2 pictures below and help me figure out what the 2 circled transistors are. I pit a TO-220 and a TO-92 in the photo just for size comparasion.
I believe these 2 transistors were taken out from an old Panasonic car stereo.
The markings B122, LB122, MXLB122 bring up nothing similar in common datasheet sites.
Thanks in advance.
these 2 transistors were taken out from an old Panasonic car stereo.
Often car radio manufacturers used transistors that were specially made for them and so they do not appear in the catalogs.
Do these work or do you want to test them?
Or do you want to replace them with a working one?
The stereo has been dismantle because the removable front was stolen. Since buying the replacement for the head unit from was almost as expensive as a brand new unit, I seized the opportunity to justify an upgrade to the car!
So I took everything apart just for the parts, and I was wondering what kind of use I can do with these. I`ll see what results I get from each pin combination on a multimeter.
Well you need a little bit more than just a multimeter. You need to test the transistor in the different configurations it can have, to find the pinout and if it is an NPN or PNP.
This project does this automatically but there is nothing to stop you just wiring up each combination and taking the readings with a meter.
An ohmmeter will work just fine. A transistor can be thought of as 2 back to back or front to front diodes... the base is the diode common so measure lead to lead reversing the meter on each measurement. A diode test function on a DMM is even better the B - E junction will be about .6V (on my Fluke 179) positive lead to the base negative to the emitter junction will read .68V and from base to collector will read .68V as well on a new unused NPN 2N3904 transistor. A same new... PNP 2N3906 reads the same approximate voltages on "Diode" on my Fluke... negative to base and positive to collector, emitter. If you can't find the conductivity or continuity (about 450 ohms on my Fluke) then it is likely the part is a regulator. I googled it and found some russian stuff only... there it either was a MJE13003 or possibly in another post on that same site a 5V 'something'... Very possible it is a Mosfet for motor control on the CD deck, the tray and spindle motors are carefully speed controlled and that might well be the pass transistor. If the center lead is connected to the tab and you cannot find any continuity from any lead to any lead or just from the tab to either but not both it is more likely a Fet and the diode you measured was the "Body" diode or internal back emf diode... with a 5V supply and a 1K resistor it would be easy to determine what it is. as any current is limited to 5mA... Really pretty safe.