transistor madness

[nopainkiller]

this is madness! Can someone fill me in on the madness??

Only time I had delt with transistors was with the little chip amps I was making, I used mpf102s. I thought this was simple enough. Then I decided to make some pedals. I bought some 2N5133s for the LPB-1 booster...and the pin-out was totally different! I couldn't find it online, but I ofund something that told me to use the hFE (wutever that stands for) setting on my multimeter to find the pin-out. I did this with the 2N5133 and got readings with the pins in two different configurations! And on both, the NPN and PNP sides. I figured the highest reading was the one to use, and it worked. I don't even know what I was reading though. Can someone tell me what I was testing for? It read 700-1000 for the MPF102s and like 400-600 for the 2N5133s, I tested them all, and used the highest rated ones. They sounded louder more gainier.

Now I just got a buncha J201s and 2N5088s and I also found a buncha 2N3904s and 2N3906s laying around. I tried testing them and had the same problem, switching it around and bending the leads to fit into my meter to find some sorta reading. Again getting things in just certain different pin congifurations and on the NPN/PNP sides. Not certain how to use it. Sorry I explain so much, It's just that I want to get across exactly what I don't understand I guess.

Also if anyone knows offhand, what would be good to sub for 2N5088? I just found some 1N4148 diodes lying around too ( I gather these diodes and transistors are pretty common?) and wanna make this simple project I found.

http://www.beavisaudio.com/bboard/pr...p_BazzFuss.pdf

Anything cool I can do with these 2N3904's and 2N3906's?? Guitar related?

[Enzo]

First line of defense is google. enter the part number - "2N5088" for example - and in the results there should be data sheets. Look at the data sheet.

Also, if you find a part in the online catalog at Mouser or Allied or Digikey or wherever, there is usually a link to a data sheet.


Most of these small transistors are in plastic packages (plastic bodies). The types have "TO" numbers . TO for Transistor Outline. The small ones are TO92 That is the ones that are flat on top, round with a flat face on one side - a row of three legs underneath. Like this:

TO92


Rear view:


USA TO92 types all have the legs ordered E-B-C = emitter-base-collector. That means all the 2Nxxxx types (2N5088, 2N3904, etc) and also the MPSxxxx types (MPSA06, MPS8098, etc)

Asian types are usually in the 2Sxxxx sequence. There will be a letter and then numbers after the 2S. A or B means PNP, while C or D means NPN. The numbers mean nothing, they are just issued in order as parts are invented. SO part numbers are like 2SA733, 2SA1015, 2SC1815, 2SC954. Asian transistors have the leg sequence different, it is almost always E-C-B.

That order is left to right looking at the flat face where the number is printed.

There are also what I call the European sequences - rightly or wrongly, it seems to me that's where they all came from. These are types with numbers like BCxxx or BDxxx. BC550, BC560 I see a lot. I for the life of me can never remember the leg sequence on those, and I look them up every time.

Here is an extra rule: since Asian types all start with 2S, they usually leave the 2S off the part as understood - it makes more room for the other numbers. So a 2SA1015 will only say "A1015" on the part itself. SO when looking up a 2S part in google, always add 2S. Google will find 2SA1015, but will not likely find A1015.

These notes so far all refer to TO92 bipolar transistors only. (For ease of typing, I am now going to abreviate transistor as "xstr.") There are other shapes. for example the power xstrs that look sorta like cowboy hats are TO3:


Tab tops are often TO220:


ANd so on.

Now then, having covered bipolar xstrs - that means the NPN and PNP types, the ones with emitters, bases and collectors - we also must consider JFETs. FETs are field effect transistors. They are very differnt from bipolars. Your MPF102 was a FET, while the 2N5133 was an old bipolar type. SInce FETs have source, drain, and gate legs, of course they are different.

Any of those J numbers are FETs - J112, J274, J201. As far as I can tell, there is zero scheme to the legs of FETs Any one of the legs could be the gate, and the other two be the source and drain. By the way, the source and drain are more or less interchangable - get the gate right and the other two will be OK. Oh all the Fairchild J112s will be the same, and all the Moto MPF102s will be the same. BUt while a J175 and a 2N5462 might be equivalent, the legs are in different order, so if you install one where the other was, you have to turn the part sideways or backwards.

But JFETs have an interesting quality, they are ON until turned off at their gate. That makes it easy to ID the gate leg. Set your meter to ohms, and measure between the three legs. The pair that have maybe 200 ohms between them - they seem shorted - are the source and drain. The one not connected to the others is the gate. Then flip to diode test, and the gate will act like a diode connecte to the source-drain. So if you see S-D-G, that means source-drain-gate.

Transistors are remarkably flexible in substitutions. Your 2N5088 is a low-noise NPN bipolar xstr. 2N3904 is a general purpose NPN bipolar xstr. Their ratings are similar. You could interchange them. The lower noise RATING of the 2N5088 might or might not show up in a particular use. Certainly if it were turning a LED off and on noise wouldn;t matter. 2N3906 is the PNP version of the 2N3904 - its complement.

I stock a WIDE variety of xstrs. I often sub types. I think I keep 2N5088, but other low noise NPN TO92 types I keep are: MPSA18, MPSA09, 2N5089 (5088's brother), MPS8097, 2N5210, MPS6521, 2N4124. I am used to them all, and frankly I might chose to use a 2SC1815, remembering I need to turn the xstr sideways to make the legs work. Remember the 2N5088 is E-B-C and 2SC1815 is E-C-B. There aer certainly other low noise types to chose from.

And you may well find that general purpose ones have low enough noise that they work fine too. That opens up other possibilities like the MPS8098, 2N3904, 2N4401, MPS2222, and on and on.


hfe means gain. And bipolar xstrs can have some gain when run backwards. But the more gainy direction is the "right" way.

Does your meter have diode test function? If so. put the red probe on the base lead, and touch the black to the E or C lead. If it beeps and gives you a reading of half a volt more or less, then it is an NPN xstr. if it reads onep, try the black lead on the base. If thay way beeps and gives the reading, then it is PNP.

Your JFETs will identify the gate, and thats it, but since S and D don't matter most times, that is all you need.

The best thing to do is look up the part first, then you'll have something to expect. Verify with your readings the part seems OK or not.


This is no mystery, it is just something to learn. You didn;t know what notes the strings on a guitar were until someone showed you. If you knew nothing of tubes, would 12AX7 mean anything? EL84 and 12AX7 have the same pins on the bottom, are they interchangable? If you needed a 6L6, would a 6L7 be OK to use? If you read about "octal tubes" or even "loctal" tubes, would you understand that? Until you learned them, I bet they were mysteries too.

How many songs do you know? You weren't born with then, you learned them all. I bet you know thousands of note patterns.

The real mystery is women, all this stuff is just things to learn.

[nopainkiller]

Argh! Yes so much to learn! It seems like you're a freakin encyclopedia! I have to read that stuff again.

My meter doesn't beep. No sound it just has numbers. It does have a diode test setting.

[jrfrond]

The real mystery is women, all this stuff is just things to learn.

Uh-huh!!!

By comparison, all of the transistor stuff is a piece o'cake.

About transistors: good, experienced techs can and do come up with subs all the time, but it is tempered by the knowledge of what you can and cannot use. People like Enzo, myself, my staff techs and probably a bunch of other guys here, have assimilated the knowledge and use it as necessary. For general purpose, low-level audio preamplification purposes as described here, with stomp boxes etc., there are LOTS of transistors that can work, but when lots of gain is called for, low-noise, high-gain types are often employed. However, most well-stocked shops will carry several-hundred transistor types for accurate replacement in ALL applications. Don't let the numbers scare you though. You can do a lot with just a few types.

Just FYI- if I was building a simple gain amp for guitar, I'd probably stick with a JFET opamp and a single-ended supply. It's really so much easier to implement and you can "do things" with the opamp design.

[nopainkiller]

Hey, are you talking about my bridged lm386 amp? Would that be a class B amp or something? Or were you talking about the bass fuzz schematic I was trying out? From what I'm reading, the bass fuzz is just a class A amp isn't it?? Is that what you mean by single ended supply??

[nopainkiller]

I tried the bass fuzz schematic with the 2N3094 instead of the 2N5088 twice. I thought I got the pin-out wrong. But nope. Still get just a hum with no signal when I turn it on. The bypass works, so I know it's not like a ground thing or something. Dammit

[nopainkiller]

tried the 3906 too, this time there's no noise. Just nothing. I didn't have any sockets left, soi I built it without and It sucks resoldering the stupid transistor in. I've done it 5 times now. Stupid transistor madness. I'l just order the right kinds, I guess and some sockets, and wait a couple weeks. BAH!

[Enzo]

Did you consider it might not be the transistor's fault? Maybe something else is wrong?

2N3904 and 2N5088 are functional equivalents. If it doesn;t work with one, it won't work with the other.

You say bypass works, but what if you have the input and output wires reversed on the switch? Just an example.

[nopainkiller]

No I checked for that. No bare wires are touching either. I also checked for cold joints, there's only three solder points on the little peice of board I used. A ground from it to the output jack, which has a wire to the input's ground, which goes to the 2.1mm dc jack ground. So it's not grounding, since the bypass works. I haven't tried soldering in the transistor EVERY whcih way. I guess I'll keep trying, Hope the sockets come tomorrow but its alot of trouble for something that should be so simple. Could it be bad transistors?? Maybe the 1 meg resistor I put on the input to ground? Everything should be fine! The schematic can't be bad can it?

[Enzo]

How can three solder joints mount 5 parts?

Your 2N5088 or 2N3904 are wired the same. They are E-B-C. Look at your circuit. Besides the diagram, there is also a pictorial of the wiring. It clearly marks the legs of the transistor as e-b-c.

SO verify: does the left leg - the emitter - go to ground?
does the center leg (base) connect to the input cap + end and the lined end of the diode? (I think they drew the cap backwards.)
does the right leg, the collector, connect to the 10k resistor, the other end of hte diode, and the + end of the output cap?

In electronics, if something doesn;t work, A. it isn;t always a bad transistor, and B. it is not a matter of solder everything in facing a different way to see if it might work.

COnnect your meter to ground, now probe the three legs of the transistor. Is there a + voltage at B and C? Is there zero volts at E?

With the thing connected to a battery, of course.

COnnect it to an amp, and connect the battery, leave the input empty. In fact disconnect the input so the cap is floating. hold a small screwdriver blade or unbend a paper clip - something metal. Now touch both ends of the output cap with it, one at a time. DO you get the hum from the amp from each end?

How about when you touch the C leg of the transistor ?

And touch the base leg in the center, any hum?

[nopainkiller]

well, after getting the sockets I just rebuilt the thing. It's in such a small enclosure, there's no room for a battery. It's just a dc plug. The box is 3X2 from radioshack. It's so small. It works now. When rebuiding it I noticed the diode was in backwards. Other than that, I dunno what it coulda been.

Its cool that I can make something without having the proper transistor around. Thanks for helpin me with this stupid little fuzz. I just got some hitachi 2SB77 germanium transistors to make a rangemaster treble booster. They came with a note saying they were tested with certain resistors for the right bias or something. The schem I have doesnt have the same values, so I'm just gunna build it and see what happens I guess.

[Enzo]

If that diode is in backwards, then the base of the transistor will have a hard time turning on.

Glad it works for you now.

[nopainkiller]

2SB77

I just built the rangemaster from this schematic. I used the hitachi 2SB77 germanium transistor instead of the one listed. It doesn't work, and I was wondering if I messed up again, or if these two resistors are interchangable. The transitors arrived with a note sayind they were biased for certain resistor values or somethig, and reffered to a schematic on smallbearelec.com for the rangemaster. I can't find it, only the bear blaster or something, and on Geofex an austin treble blaster that is different. Ami I just makin too much of this? I shouldn't build stuff at 5 in the morning I guess. It's alwayss broken!

[nopainkiller]

Is it just me or are the caps and the battery drawn backwards in this schematic??

[R.G.]

Is it just me or are the caps and the battery drawn backwards in this schematic??

No, they are absolutely correct - for that particular circuit.

What follows is not intended to slight you or your enthusiasm. It can take a lot of reading and study to learn all the things you've touched on in your posts here. There are definite ways that electronics works and does not work. I personify the physical universe as Mother Nature and Her Rules.

Mother Nature enforces her Rules without pity or flexibility. If you don't understand them, you'll be very, very frustrated. If you learn her Rules, you can get them to work for you. But Mother doesn't care whether you have any opinion about the Rules or not. They just are.

It's best to get in the mind set that you're going to have to go attack learning the Rules, while keeping in mind that there may always be more Rules to learn no matter how much you've learned already. Getting frustrated, or insisting that you did it right and the Rules are wrong won't help. Mother doesn't care what you think. She just keeps the Rules.

Dig in, and work your way up the slope. We, all of us here, are only at varying places on the slope. We might be a little ahead of you, but none of use are at the top. There may not BE a top, only more slope.