Did I make a bad purchase with these 2n2222A's?

[GuitarMatt]

So I have nearly all the parts and most of the know-how to finally create my first build. I'm sitting on a bunch of silicon transistors with gains in the mid 200's. I need some with gains closer to 100 to make some decent stompboxes, so I ordered some 2n2222A's from a reputable eBay seller, claiming that these transistors " can switch up to 40V at peak currents of 1A (not continuously, just peak!), with a DC gain of about 100. "

Now my understanding is that the hfe should be around 100, but I got them today, and tested them with both a built-in multimeter tester and the GeoFX transistor tester, and they all have gains around 250 with little variation. None are below 200.

So what am I missing? Is hfe of 250 considered to be "around 100"? Is DC gain not the same as the hfe referred to on these boards? How can I reliably buy transistors with gains that are actually around 100?

[Kipper4]

What does the data sheet for your jellybeans range of hfe?
If they're within that tolerance then I could be human error or a misleading description on behalf of the seller.
If it's the latter then ask for a refund if you cannot make them work within the circuit.
It's a bit hard to tell without a diagram if they can be made to work.
Good luck and welcome.

[slashandburn]

What are you planning to build with them? They might be fine.

I only have a few 2N2222s left but iirc they're in the 150 - 250 hfe range.

If you need closer to 100 hfe perhaps a different transistor would be better suited, that said if you've been sold these having been told they're were rated close to 100 I'd contact the seller., "close to 100" is fairly ambiguous language, I'd be reluctant to jump to conclusions that you've been mis-sold.

I dont think they're off spec for 2222's but if the seller said they were close to 100 that an error on their part, deliberate on not.

[GuitarMatt]

Thanks Kipper, I have just requested the datasheet from the seller, they should get it to me within 24hours.

In the meantime, is it worthwhile to look up the datasheets for other 2N2222A transistors, or will the characteristics vary too wildly by manufacturer?

When I type in all the printed info on my transistors (which, for the record is 2N 2222A H 331) the first thing that comes up is a datasheet with the following info:



Either this is accurate to what I have and I need to initiate a return, or this datasheet is inaccurate to what I have, or I'm just still hopelessly misinformed. 

[slashandburn]

  Is DC gain not the same as the hfe referred to on these boards? How can I reliably buy transistors with gains that are actually around 100?

I've assumed DC gain and hfe to be the same, but I barely know what I'm doing.

The specs you posted (in my eyes anyway) show that a 2N2222  will be rated anywhere between 100 and 300 hfe.

[GuitarMatt]

Thanks slashandburn, I'm hoping to build silicon versions of old fuzz-face and tonebender type circuits. I could use transistors with gains even lower than 100 to be honest, but I figured ones around 100 would be reasonably versatile.

I've just seen a few posts on this forum about guys using 2n2222's with gains around 140 or so, so I didn't think I'd be off the mark too bad with this purchase, but as of now I still don't have any transistors with gains lower than 200.

Assuming I'll need to make another purchase, does anyone have any suggestions on silicon transistors that are generally useful for fuzz-face type builds with gains that are within 70 to 130?

[slashandburn]

You'll get plenty more (and better) advice from more knowledgeable people as time wears on but off the top off my head the only npn silicon transistors I've come across in that range were 2n1711, they were all around 80 to 100 hfe. I think I ended up using them as Q2 in Meathead builds.

I say build whatever your going to build with sockets and swap in lower gain transistors as and when you get them if you're not happy with how the current batch sound.

In the grand scheme things, 250 hfe is still on the low side as far as silicon transistors go.

[Kipper4]

Should have guessed a silicon fuzz face.
Not sure it apples like in the germanium pnp fuzzface.
I'm no fuzzpert.

[mozz]

If you use the recommended germanium gains in a silicon build it won't sound good, or at least it won't come close to a germ build. I think you want to be 150-200 and even higher.

Are these in the metal cases? I got a bit less than 1000 in a factory box STI and they are measuring 98-130. I have PN2222a and MPS2222a and they are higher. I have seen PN part numbers have a different spec sheet than a 2N sheet.

[slashandburn]

I'm even less of an expert than kipper. From what I gather the 2n2222 is a good choice for a Si Fuzz face.

Socket the transistors. Build it. Try it. Swap them out later if you're not satisfied.

[patrick398]

For silicone FF try BC138 or BC108, I think 70s era FF used those

[PRR]

The text-table you cite is the 1960s RETMA(?) registration. Any "2N2222A" SHOULD fall in these specs. You will notice they are VERY wide, and mostly open-ended.

The hFE of a specific individual varies a LOT with current.

> between 100 and 300 hfe.

At 100mA current! We don't run pedals that hot.

We also do not know if the two testers test at a current remotely similar to the currents in a FF.

Until you AND the vendor agree on test conditions, you do not have any valid complaint. My guess is these are 2N2222As and that at "some" test current the hFE may be "around 100".

Why don't you just try them? (There are billions of uses for '2222 even if they do not happen to mesh with any specific fuzzface.)

[smallbearelec]

When Hfe is specified for silicon devices, +/- 30% is considered relatively close. So, as others have suggested, you likely have grounds for returning if the seller promised gains of "about 100". That doesn't mean that the devices are all unusable. In my experiments:

http://diy.smallbearelec.com/HowTos/BreadboardSiFF/BreadboardSiFF.htm

the FF circuit is OK with a Q2 in the high 100s, though you should expect to have to tweak the bias resistors for best results. Also your 2N2222A are too "hot" to be good for Q1. I like a 2N4123, but that number is Not magic; many other common types get that low. Sorry, my store is not open for ordering till the lockdown in NYC is lifted. Please either check back in a week or so or do some more fishing on eBay. And do invest in a breadboard.

[GuitarMatt]

I breadboarded the FF circuit several days ago and have messed around with swapping transistors and component values, etc. It just seems too hot, and I would guess it's because my Q1 has a gain of 211 (the lowest gain transistor I have). At it's best, it sounds like a fuzz face trying to be a metal zone.

Thanks all for the help, I will probably not request a return, as this pack of 100 transistors was only 6 dollars, and I may find some use for them later. But I really only intended to build silicon versions of old 60's fuzz boxes, so I'll need to get some silicon transistors with gains that are truly "about 100".

Also to answer mozz, no these transistors are the typical modern black plastic veriety, not metal casings. And thanks for the info, I did not know silicon versions of FF style pedals require higher gain than germ.

[patrick398]

But I really only intended to build silicon versions of old 60's fuzz boxes, so I'll need to get some silicon transistors with gains that are truly "about 100".

Are you adverse to going germanium? Might be the answer to your prayers

[anotherjim]

Would it help to try "reverse beta" for lower gain? This is where you exchange the emitter and collector - although that can result in really low Hfe.

[GuitarMatt]

I'm not too against germanium, (I have some on order from Russia, but they may not get here till July  )


My biggest hurdle with germanium is the whole charge pump thing to get it to work with a typical 9V jack supply. I haven't really researched it much, and silicon just seems easier to help me get off the ground, so to speak.

I just figured since I'm sitting on this pile of silicons, and they seem to be a dime a dozen I may as well try to build some of the germ circuits I'm planning to build later with these.

And to anotherjim, I can try to reverse beta, but I have never heard of that before. If I do that on a transistor with gain of 250, what could I reasonably expect the new gain to be? Edit: I just reversed some with gains of about 280 and they came back at 20 or lower. Interesting, but probably too low to be usable.

[slashandburn]

>> I will probably not request a return, as this pack of 100 transistors was only 6 dollars

Hold the phone. 2n2222 at 3c each? Does this seller have any more of those?

Edit: 6cents. I can't count at the best of times but Its also late and I'm drunk.

[GuitarMatt]

>> Hold the phone. 2n2222 at 3c each? Does this seller have any more of those?


Go crazy. Or let me know if I bought the wrong thing outright: https://www.ebay.com/itm/163662244123

[mozz]

 I don't know if he is a "reputable" seller, looks like he just resells chinese stuff. I asked if they were the metal can type because if you go to digikey or mouser 95% of them are the metal can variety. TO-18. If i see a TO 92 package, it is most likely some other transistor that way exceeds the 2n2222a spec, and is relabeled. I really hate buying devices on eBay becuase a lot are relabeled, or fakes. Now find a seller who has old stock, old date codes, they are most likely legit and adhere to the original specs closer. I spend a lot of time unsoldering parts from old circuit boards i know were made in the 50's 60's 70's, today was pairs of OC45, OC71,OC72. Made my day.