transistor madness

[Enzo]

No they are right. NPN and PNP transistors work the same, but they work at opposite polarities. PNP transistors work on negative power supply. If you put your battery the other way, it won't work.

[nopainkiller]

Oh, well I hooked up the battery and the caps backwards then. Thanks. I thought it was just misdrwan on the schematic. I thought it might take negative current but came on here to ask instead of wiring it all again. I've only heard of it being possible to do that, I've never seen it or had to buil like that before. I can't afford more parts. Even if they are 25 cents at radioshack, I don't have gas. That's the only reason I'm doing this. Cuz I can't afford to buy my own pedals and amps! I've only been at this for a few months, and I do read. It's hard to learn everything from reading, I need experience.

[nopainkiller]

there's something I'm not getting here. I turned the caps around, and grounded the positive side of the battery, and changed the negative side to the supply. This time, the led turns off right when the power is cut. Before it would dim slowly after shut off. And there is a hum when it is on as oppsed to just nothing. But it's still just a hum. I've tried the resistor a buncha different ways. It's a asian transistor so I tried it the way Enzo said, it didn't work either. So I tested it again, and put it in the way it read on my meter. nothing. GAH! Are germanium transistors finicky or something??

If I try and find the 2SB77 datasheet, or any other for that matter, I just get a hundred results of sites that search datasheets, and pages where I have to click the "2SB77" link 4 times before I get to a page that says there is no datasheet on file! No datasheet! I also get a hundsred difefrent forum posts asking what the hell the pin-out for this thing is, and that they can't find the datasheet!

I don't mean to troll. It's just I can't just find the answer to my problem. I don't even know what the problem is! This is the last time I will bug you guys. If I get this rangemaster working, I will be done! I will retire my iron and take up something I have the apptitude for. But I want this freakin rangemaster!! GAH!

[Enzo]

There must be someone in your area with electronic knowledge, you know? See if you can find someone willing to help a little. When you don;t really know what you are looking at, it will be difficult to see what is wrong. Like trying to grade term papers written in Japanese.

There are amp shops out there I know, and there are also people like amateur radio operators who are often helpful. The local schools might have electronics clubs where you might find helpful people.

We don;t mind trying to help here, but there is a limit to what we can do from afar. I help local guys in my shop all the time.

Parts are reasonably resilient, but if reverse voltage is applied they can be destroyed. I don;t call that finicky, it is just one of those rules. Like connecting the jumper cables backwards to jump start a car - it likely will ruin the electrical system and/or explode a battery. When a circuit doesn;t work, we then have to take voltage and resistance readings to find out why. We also test parts to see if they still work.

I can tell you one thing, soldering parts in every direction you can think of is a good way to burn out parts with polarities - like transistors, diodes, and caps.

[nopainkiller]

the tranny still measures gain on my meter. And I tried one that was untouched with the same results.

I guess I will rebuild the thing form scratch like I did the bass fuzz. Glah! But this time there sin't a diode in backwards!

Would biasing be a problem?? Does the transistor have to turn on or something?? Because I'm not using the values specified with the transistor. They are pre sorted and selected and packadged with recommended resistor values, for biasing. Wutever that means. I was having a hard time understanding even which resistors they meant. Now I know which resistors I'm using, instead of 43k it's 68k instead of 2.7k it's 4.7k. It's just that I don't think I'm using the same schematic as they thought I would be. And I can't find the one they want me to use.

[nopainkiller]

with a PNP design, do I have to use the RING of the inpts and outputs and the tips as grounds???? Stupid question yes i know.

[Enzo]

If you built a circuit based on a 2N3904, You could change to a 2N3906 by merely swapping the battery terminals and turning all polarized caps and diodes the other way.

Input and output have nothing to do with transistor polarity

[nopainkiller]

yes, I've reralized this. And have been looking at some fuzz face schematics That use the 2N3906 and some NPN versions too. Found alot of other things I can use those 2N3904 and 2N3906s.
But I can't get this rangemaster to work.

[nopainkiller]

Success??

I rebuilt it using the schematic below. There are a few differences. But when rebuilding I noticed the pot was in backwards!!

But I don't think it's working right. In fact it's not. it's supposed to be a treble booster. But it just cuts. When I turn it on it's a cut! With a tiny hum behind it. GGGGGGARAARrr!!

I pulled out the germanium 2SB77 and put in a 2N3906 just cuz I knew I could. Got similar results. Actually it was a bit louder and clearer. But still a cut. Oh man! Wut is goin on! Just crappy wiring?? Could my soldering just be this bad???

[nopainkiller]

forgot the schem:

[nopainkiller]

Success??

I rebuilt it using the schematic below. There are a few differences. But when rebuilding I noticed the pot was in backwards!!

But I don't think it's working right. In fact it's not. it's supposed to be a treble booster. But it just cuts. When I turn it on it's a cut! With a tiny hum behind it. GGGGGGARAARrr!!

I pulled out the germanium 2SB77 and put in a 2N3906 just cuz I knew I could. Got similar results. Actually it was a bit louder and clearer. But still a cut. Oh man! Wut is goin on! Just crappy wiring?? Could my soldering just be this bad???

[nsubulysses]

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.

Thanks for helping to sort out the madness with this great post

[Dave H]

An oldie but a goody

[nickb]

Indeed, a truly classic Enzo-ism. It belongs in the hall of fame.

[Dave H]

An oldie but a goody

That applies to Enzo too.