TI 2N388, hfe too low

[mac]

I recently purchased a bunch of TI 2N388 (see my pict). I was dissapointed when I measured the transistors using RG method. Highest hfe is about 60, the average <hfe> around 35, leakage under 40uA, room temp 16ºC or 60ºF. I was expecting values near 80 - 90.
RG test put 4uA of base current, the same amount a good fuzz face should have.
I scaled the method down, ie, rb = 220k and rc = 0.245k. With these resistors the base current ib is 40uA, and <hfe> increased by 1.7 - 1.9X, leakage almost unchanged.
I guess that hfe is too low because:
1. Test temp is low, most likely. It's fall and I'm replacing the heating system, ok? 
2. Defective devices. But they sound good!
3. hfe = hfe(ic). Maximun hfe is at higher ic values than in a fuzz face.

I'd like to hear your experiences with these transistors.

mac

[Stephen]

I have the 2N388A and they sound amazing!! NPN germanium is that what you have??     All of them are good I test them simply with a meter...I know that is not right but you can watch the change in leakage as it sits and they are really a good transistor for my rangemasters and fuzzes!!!     See how they sound maybe you are having false readings??

[mac]

I have the 2N388A and they sound amazing!! NPN germanium is that what you have??     All of them are good I test them simply with a meter...I know that is not right but you can watch the change in leakage as it sits and they are really a good transistor for my rangemasters and fuzzes!!!     See how they sound maybe you are having false readings??

They are texas instrument npn ge. According to specs hfe should be higher. And as far as i read, people in this forum reported hfe values around 80 - 90 using RG test. That's why I purchased them without testing them at the store
No false readings, no mistakes during test.
Today I tried them in a tonebender mkii and in a range master. They sound amazing even though gain is not in the recommended range. I compared the results with a set of 2SA102 pnp ge with the right gain and they sound almost identical. Well, the pnp sounded a little better to me.

mac

[R.G.]

Three comments come to mind.

(1) As I've said before, unless you're willing to buy the parts and take your chances on having to throw 100% of them away, only buy germanium from people you pay to take that chance for you. On previously untested lots of germanium I count on 66% failure. Some lots I've bought have clearly been pretested by someone else who sold off the rejects and I had up to 100% failure. Assume anything  you buy on ebay has been picked over at least once.
(2) As I've said before, part number means almost nothing in searching for good germanium. Germanium had even wider variation than modern silicon, and was often pretested by the makers, and the fallout sold as "off spec" to resellers. The part number is nothing more than a suggestion that it might work. Unless you're willing to buy the parts and take your chances on having to throw 100% of them away, only buy germanium from people you pay to take that chance for you.
(3) On the other hand, if they sound great, what is the problem??? 

[mac]

Three comments come to mind.

(1) As I've said before, unless you're willing to buy the parts and take your chances on having to throw 100% of them away, only buy germanium from people you pay to take that chance for you. On previously untested lots of germanium I count on 66% failure. Some lots I've bought have clearly been pretested by someone else who sold off the rejects and I had up to 100% failure. Assume anything  you buy on ebay has been picked over at least once.
(2) As I've said before, part number means almost nothing in searching for good germanium. Germanium had even wider variation than modern silicon, and was often pretested by the makers, and the fallout sold as "off spec" to resellers. The part number is nothing more than a suggestion that it might work. Unless you're willing to buy the parts and take your chances on having to throw 100% of them away, only buy germanium from people you pay to take that chance for you.
(3) On the other hand, if they sound great, what is the problem??? 

100% right.

I bought these "off specs" 2N388 while I was in Buenos Aires resting for a couple of days. I did not have my 'calibrated-with-RG-test' DDM, but for half a dollar each I took the risk and bought 10. Probably if I had my DDM I would not have bought them. Now that I finished an amazing npn tonebender mkii (hfe: 40, 50, 61) I thank Mary Magdalene & husband  I have not taken my DDM with me 

mac

[R.G.]

Cool! In the end, your ears are the measurment instrument that counts most!

[mac]

Cool! In the end, your ears are the measurment instrument that counts most!

... when they are wax free 

[LightSoundGeometry]

http://www.pedalpartsplus.com/mm5/merchant.mvc?Screen=PROD&Store_Code=PPP&Product_Code=4104&Category_Code=GTRANS

Beta of 38.  Uf 181mV

doesnt work on any of the circuits I have breadboarded.

I keep reading and hearing people on youtube saying they have fuzzes/RM's with GE around 40..is this possible?

I thought these particular trannies were supposed to be for the RM and around 60-120 or so ?

http://www.datasheets360.com/part/detail/2n388/-4819818350242825997/

says beta minimum 60

* the people on youtube saying this also happen to be selling them ..me thinks people sell bad stuff in hopes a newbie cant get a circuit going anyways and never realizes its the bad part or else how can people get away with selling this stuff?

and people complain small bear charges a fraction more is crazy !!

[PRR]

> Maximun hfe is at higher ic values than in a fuzz face.

Yes. hFE is specced for 30mA, instead of the 0.3mA-1mA used in FF. This is a *200mA* part, old technology, and it is reasonable to suspect hFE has fallen when you get way-way down in current.

If you care if it meets its original *computer* specs, around 30mA, wire 120 ohms from (fresh!) 9V battery to collector, 8K collector to base, emitter back to battery (right polarity). If the collector sits at 4.5V to 1.7V, it is in-spec *for 30mA work*.

Working in a FF and not happy? Post voltages. Particularly both Collectors. There is some leeway in the FF to allow for different transistors; or we may be able to show that this transistor can NOT be happy in a FF.

[mac]

doesnt work on any of the circuits I have breadboarded.

Harmonic Percolator calls for hfe(40-50) but a bit of leakage, 100ua or so.

I keep reading and hearing people on youtube saying they have fuzzes/RM's with GE around 40..is this possible?

Yes, it's possible. You need to change or add extra bias resistor in some cases.
The question is, are you going to like it?

Take the RM for example. You can put a hfe=40 germ in it, and tweak base resistor to set the collector near 7v. Piece of cake, but will you get that typical distortion when you hit the strings hard?
BTW, I never tried such low gain transistors in a RM.

mac

[mac]

> Maximun hfe is at higher ic values than in a fuzz face.

Yes. hFE is specced for 30mA, instead of the 0.3mA-1mA used in FF. This is a *200mA* part, old technology, and it is reasonable to suspect hFE has fallen when you get way-way down in current.

A few after starting this old post, I tested hfe=hfe(ic) for some transistors, in particular power ones for amp stages, ACxxx, 2SD72k, 2sb56 and similar.
I noticed that hfe fall fast when ib goes to FF values.
And I wonder if this is the reason why ACxxx clean better than others in a FF when you decrease the guitar volume...

mac

[smallbearelec]

The very low-gain 2N388s sound like they would be prime candidates for a Darlington Rangemaster or Fuzz Face:

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

[LightSoundGeometry]

okay, i will try and put different circuits on the breadboard and see if it works in any of them. i appreciate the responses. i wasnt sure and was just checking.

[LightSoundGeometry]

> Maximun hfe is at higher ic values than in a fuzz face.

Yes. hFE is specced for 30mA, instead of the 0.3mA-1mA used in FF. This is a *200mA* part, old technology, and it is reasonable to suspect hFE has fallen when you get way-way down in current.

If you care if it meets its original *computer* specs, around 30mA, wire 120 ohms from (fresh!) 9V battery to collector, 8K collector to base, emitter back to battery (right polarity). If the collector sits at 4.5V to 1.7V, it is in-spec *for 30mA work*.

Working in a FF and not happy? Post voltages. Particularly both Collectors. There is some leeway in the FF to allow for different transistors; or we may be able to show that this transistor can NOT be happy in a FF.

its off the bread board right now as i am using the BB to work on something else. I got tired of fooling with it finally and want to mess around with a few other things I been wanting to experiment with like cap switching and diode switching in a distortion. before I took it apert, I had it around 4.5, then around 7 and then straight 9v on the Collector.  lol. I am able to put any resistor anywhere in the BB and measure voltages but it seems only certain ones work.

I am certain its my lack of knowledge, but asking these questions and getting responses from this board helps me understand things better. so much more.  I need to seek out a schematic that calls for a low beta and retest the circuit with transistor. I apologize to any with my stab at selling bad parts !