Hi all,
This threads probably a waste of time, but i thought i would just throw it out there anyway.
I bought a bunch of russian germaniums (hah, you already know where this is going?). The box was sealed. There is no way anyway could have gotten inside this thing without destroying the delicate paper holding it together. The datasheet iINSIDE THE BOX says hfe 80-150. so...you know...their GOTTA BE 80-150 right? well, the HFE is measuring much lower.
So...must be a shunt resistor. I know the Peak cant measure hfe with shunts accurately, i checked the manual. Is there no other way of measuring HFE for transistors with shunts? I assume you cant measure the shunt resistance accurately?
Only other idea i have is to measure them all, and group them together ("bands"). I have 100, so i could probably, roughly guess where they sit on the scale of 80-150...that and actually plug them into a circuit and listen of course...
Thanks for any help / info!
Paul
what type of transistor? and what hfe are you getting? and are you somewhere cold ;D
GT308V's i think reputably have shunt resistors. I only measured about 5, id say they were all 60-70ish. Its about 20 degrees so 'normal' sort of temperature.
I wacked a random one in by buzzaround clone and it sounded pretty good! Not conclusive though, as i need to put in a low hfe ge in q3 on the buzzaround and see if that sounds remarkably different. ie, not sure how my buzzaround reacts to a low hfe q3.
Paul
That Cyrillic V is actually a B, by the way, for the higher gain sorting.
60-70 is pretty good for GT308V, if you search this site, many people get hfe in 40s.
Not sure how temp dependent more modern, russian germanium is, to be honest. Try holding them between your fingers and see if it goes up.
I have bought a several boxes of GT308 and they typically come in around 40-60 when measured. I like them and use quite a bit.
yep, those commonly have gains in the 60-75 range with small % above and below
if the peak doesn't show "resistor shunt" it probably doesn't. if it does show "resistor shunt", then it does or it's possibly a bad transistor
I've had better luck with the military version of those, the 1T308V, but still much lower hfe's than on the datasheet
For the Buzzaround, they're great for Q1/2 darlington, but Q3 is more dependent on leakage...you need much higher leakages to hear big differences....and there is!
I dont have a peak, but i have read people have tested them with a peak and there is a shunt resistor reported by the peak. I dont think that the gains im measuring are accurate. The datasheet says 80-150. Some variance might exist, but from 80-150 to 60-70 or less?
To be honest, i havent tested gains enough to actually no what ive got, but from 4-5 quick collector current tests i hastenly did last night, they seemed low (60-70ish). I'll measure some more tonight.
I still think these are measuring low because of the resistor shunt...Theres no reason why they would put 80-150 on the datasheet when they dont measure anywhere near that...Was the ambient room temperature 100 degrees? :)
If you cant measure HFE for transisors with a resistor shunt, im going to just have to sort these by ear i guess :(
These i have are listed as IT308B's = GT308V's btw.
Paul
Quote from: chromesphere on November 07, 2012, 06:08:14 PM
I dont have a peak, but i have read people have tested them with a peak and there is a shunt resistor reported by the peak. I dont think that the gains im measuring are accurate. The datasheet says 80-150. Some variance might exist, but from 80-150 to 60-70 or less?
yep, and the "G" version more than the "1" version, since military will be closer to spec. look what this seller (he's good) writes:
http://www.ebay.com/itm/1T308V-GT308V-PNP-120M-Germanium-Transistors-AF109-20pc-/370510158187?pt=LH_DefaultDomain_0&hash=item564420596b
"VERY LOW LEAKAGE transistors! Several customers who bought and tested these transistors reported that ALL transistors they received had leakage currents LESS THAN 10-20uA. On the other hand they reported that HFE usually is about 80 or just under 80."
I've had hundreds of those and they never measure "resistor shunt" on the Peak..and RG's method measures very close to the Peak.
Quote
To be honest, i havent tested gains enough to actually no what ive got, but from 4-5 quick collector current tests i hastenly did last night, they seemed low (60-70ish). I'll measure some more tonight.
either way, they are still great for a variety of fuzzes, especially Fuzz Rites & variants or anything with a darlington pair.
Quote
These i have are listed as IT308B's = GT308V's btw.
what is on the case? something that looks like a "G" or something that looks like a "1"?
edit:
(http://www.luciferstrip.com/fuzz/1T308B-specs.jpg)
On the box it says "IT308B". So i assume these are the non-military spec.
So these dont have a shunt resistor and are just really low hfe? That's really deceptive of this company to claim higher hfe's when they are no where near it...I mean...if i was an electronic circuit designer and im looking for a transistor to use in the circuit "IT308B should suit!". Buy 10,000 of them. "oh look at that...hfe is way off"....i no they can sometimes be off, but you know...less then 50%? It just doesnt make any sense... :(
One other thing that i dislike about these. There is no indication of which lead is emitter. The datasheet is totally ambiguous. There is no distinguishing feature that marks the any of the leads. There are markings on where the product code is printed on the transistor, but i have found that the print is in different position from one transistor to another making the printed markings totally useless. Infact i'll extend this rant to all russian germaniums. Wheres the freaking pinout standard? E B C. Like everyone else....It's mental...
Ok, end of rant :)
Paul
Quote from: chromesphere on November 07, 2012, 06:58:16 PM
On the box it says "IT308B". So i assume these are the non-military spec.
I meant on the actual metal case of the transistor. 1T308B is the military one
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So these dont have a shunt resistor and are just really low hfe?
not that I found...and they don't behave any differently than i would expect from a 60-80 hfe ge
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That's really deceptive of this company to claim higher hfe's when they are no where near it
i think they are still ~ 25 yrs old...how much do hfe's change...there's little leakage, so I'd guess little?
Quote
One other thing that i dislike about these. There is no indication of which lead is emitter.
there's a small dot on top, on the rim above the emitter
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Wheres the freaking pinout standard? E B C. Like everyone else....It's mental...
there is no standard....
edit:
I use this site for most of my ge lookups, including US, UK & Jap
http://transistor-spravochnik.ru/description/gt308v/38335
http://transistor-spravochnik.ru/description/gt308b/38333
Quote from: LucifersTrip on November 07, 2012, 08:04:31 PM
not that I found...and they don't behave any differently than i would expect from a 60-80 hfe ge
Hey Lucifer,
The data sheet says 80-150....are you saying that its normal to expect a HFE of 60-80 hfe from a claimed 80-150 ge?
Ill have to check the metal casing when i get home tonite.
Paul
Quote from: chromesphere on November 07, 2012, 08:17:14 PM
are you saying that its normal to expect a HFE of 60-80 hfe from a claimed 80-150 ge?
ge's are far less consistent than silicon...even from batch to batch...then, factor in age, storage conditions, etc...
I'm sure one of the masters can give you more details
So far all the russian ge's i have bought have been pretty acurate, except for mp21d's which still sounded pretty good. Infact they look almost the same as these ones. Anyway, ill measure them tonight and see where they sit. Chances are the gains will be similar to everyone elses; much less then stated on the datasheet....oh well...
Paul
How are you measuring?
What collector current?
Same collector current as the Russians use for that type?
Looking at the big picture, hFE is zero at zero current and sinks to zero at some huge current (tho it may melt first). There's a hump in the usable range. Since Andy Groove's work, Silicon can usually show a fairly flat top across a couple decades of current. Still you find datasheets showing hFe varying 2:1 between 10uA and 1mA. In older Ge processes the hFE was always slanty. 2N388 is specced 60-180 at 30mA but 30 min at 200mA. The popular 2N404 says 30 min at 12mA but 24 min at 24mA... 24% difference for just 2:1 change of Ic.
Thanks for the info PRR.
To answer your question lucifer the transistor has printed on it IT308B
Im using the small bear simplified GE HFE tester. So this one i have in there right now. Reads Ic 437ua and leakage 15ua. 9v power source would make that a HFE of 46.8. Nearly 50% below the datasheet minimum.
Paul
without a data sheet or Peak Atlas, how do you determine if a transistor has a resistor shunt?
Mainly from forum posts, but thing is, i think part of the problem is the confusion on the model numbers...hell, even im still confused as to which one i actually have!!
I'm going to through some tonight and write down the gains. I just tested another on then and it was 77. Almost, at the min. I still havent seen one over the min of 80 though...will update.
Edit: found the emitter dot. I can see why i missed it! Wow...its incredibly pale. Well atleast that sorts that out.
Paul
I got two lots of 50 x GT308V's and measured them all with my Peak and this is the spread I got:
Qty HFE
1 56
1 58
1 59
4 60
2 61
4 62
3 64
4 65
7 66
4 67
2 68
4 69
10 70
4 71
5 72
3 73
6 74
6 75
2 76
5 77
1 78
2 79
2 80
1 81
2 82
2 83
3 84
1 85
1 87
I got these a couple of years ago and have heard a lot of people getting much lower gain batches since.
And thats what i have been reading around the forum. So...the question...why are the HFE's so low, when the data sheet specifically says they should be 80-150hfe...I'm heading back to my original conclusion. They must have a shunt resistor...
Edit: and if such shunt resistor exists, theres nothing you can do to actually measure the HFE accurately. I'll probably have to just compare some of them to transistors i have on hand with the same hfe's and try and work out 'approx' where they sit.
Paul
I don't think there's a shunt resistor. I have a batch of GT313's which all measure around 30 to 50 hfe and they are shown on the Peak as having a B-E shunt resistor. But gain is related to current so unless you're putting the exact same current through them they used during the datasheet tests you will always get deviations in the numbers.
Quote from: chromesphere on November 08, 2012, 03:32:58 AM
So...the question...why are the HFE's so low, when the data sheet specifically says they should be 80-150hfe.
In Soviet Russia, transistor shunts you.
Quote from: Kesh on November 08, 2012, 04:34:36 AM
Quote from: chromesphere on November 08, 2012, 03:32:58 AM
So...the question...why are the HFE's so low, when the data sheet specifically says they should be 80-150hfe.
In Soviet Russia, transistor shunts you.
I think this is the most accurate description of whats giong on here :)
Found this thread. I had read it, but i didnt realise they actually came to conclusion that these transistors dont have a shunt resistor. Which means, and goes back to what prr and iviark have said. Different test configuration. Maybe they get those gains at 15 / 20 volts are something? Who knows. I'm over it :)
http://www.freestompboxes.org/viewtopic.php?f=17&t=6123
Paul
Quote from: Kesh on November 08, 2012, 04:34:36 AM
Quote from: chromesphere on November 08, 2012, 03:32:58 AM
So...the question...why are the HFE's so low, when the data sheet specifically says they should be 80-150hfe.
In Soviet Russia, transistor shunts you.
:D
Yeah, like IVIark said it should be the 313's that have the shunt resistor. All the ones I have show so on the Peak.
I haven't read through this thread completely but all the gt308s i have are much lower hfe than the datasheet says they should be. Most on the ones i have are in the high 50's to mid 60's. Out of about 100 there may be a few in the low to mid 70's.
Sorry if im way off topic here since i really did read all the thread.
> Ic 437ua
Russian 308 hFE is specified at 10mA. >20 times higher.
With a looks-like-B suffix, hFE at 10mA should be 80-150.
(http://i.imgur.com/bD1Vl.gif)
There is a "typical" (not guaranteed) hFE versus I curve which shows *steep* fall-off at lower current. At half-mA, a lot closer to 50 than the ~~100 gotten at 10mA current. (Yet awful close to your observed 46.8 hFE @ 0.4mA.)
> how do you determine if a transistor has a resistor shunt?
The diode junction is "dead" for very low voltages, yet perfect resistors are linear to infinitesimal voltage (real resistors are pretty close).
Apply a very small voltage/current and measure the current/voltage.
If you own a good-old VTVM with an ohms scale, it is easy. If you Ohm a naked junction and turn the range switch, it reads "different Ohms" on each range yet the needle hardly moves. If you look at the Volts scale it hangs with 0.6V (for Si)..... the "ohm meter" is actually finding the diode drop voltage for different currents! But if there is a shunt resistor, as you go to high ohms ranges, the "Ohms" becomes constant at some point well below 0.6V on the Volts scale. Yes, this is less useful with the 0.2V of Germanium because you get jammed in the bottom of a 1.5V range.
Where are you guys buying your 308s? I'd like to get my mitts on some consistently low leakge Russkies.
New under the sun? http://www.nxp.com/products/automotive/discretes/resistor_equipped_transistors/ the rest of the clicking is up to you (unless you want to stick to through-hole germaniums only).
Quote from: azrael on November 08, 2012, 04:57:57 PM
Where are you guys buying your 308s? I'd like to get my mitts on some consistently low leakge Russkies.
http://stores.ebay.co.uk/Orpheus-2005
http://stores.ebay.co.uk/Next-Lux
http://stores.ebay.co.uk/BgEbus
FWIW, I've bought about 15 different Russian germanium PNP transistors and with the exception of the GT402B, they all had very low or zero leakage. The GT402B did have some but out of 50 only 2 were above 0.6mA and they were higher gain than the others, ranging from 78 to 193 hfe.
Thanks for the detailed explaination PRR! Seems you were on the money the first time around! I'm getting low gain due to different test conditions, my rig's only supplying approx half a milliamp, the test conditions: 10 milliamps. And looking at that graph you found, you can see where 1ma is. Not going to get much more gain them 80! Wow it all makes sense :)
Ok so these would be more suited to higher current applications i suppose. Well still I'm getting a few around the 80's mark, so half will probably be usable in some way. I have found better results / better suited germaniums with other russians though and probably wouldnt buy these again.
Paul
Of course, another question that springs to this persons mind is, how do we increase the current to get more gain :)
Would it be possible to bias say a fuzz face or tone bender to be supplying the tranny with this sort of current? Or do you have to increase the voltage to the circuit? Might be getting a bit over my head with this question but thought i would throw it out there.
Paul
It's all relative. A pair of AC128s that read 80 and 120 hfe and sound superb in a Fuzz Face have exactly the same issue. The reading of 80 and 120 is nothing like the actual gain they're going to be providing in the circuit, it's just an easy way for us to measure them to allow us to compare for gain levels in our test, and select transistors appropriately.
I always thought the GT308's sounded great in a Fuzz Face and you'd certainly have Q1 covered, plus Q1 and Q2 in Tone Bender circuits. Maybe it's worth looking for those Q2 transistors. Like I said the GT402Bs are a good choice for higher gain, and I also got some 2N404s which were also low leakage but were again higher gain on average than the other Russian transistors I've got. Plenty over 100 hfe. Neither of these were very expensive either.
hFE=50 doesn't suck. Just use them.
Quote from: PRR on November 08, 2012, 08:25:40 PM
hFE=50 doesn't suck. Just use them.
Yeah i agree. From my experimenting, ive found only the slightest difference in gain from 50 hfe upwards. Lower though, and they lose a notificable amount of gain (in a tone bender, or i from memory, even a soul bender). I think its been drummed into people how important gains are though. I sell a few GE's every now and then, to help fund my DIY addiction, and people tend to be very specific. "Must be 70-80!!!".
Im probably just going to start a debate with these comments though :)
Paul
> slightest difference in gain from 50 hfe upwards
When I was younger the prof's quizes always stated "assume hFE >50".
By that time, improved Si processes were yielding much higher hFE at jellybean prices; I guess prof didn't want to re-type the quiz mimeo masters.
Early Ge could be sorted to hFE >50 with small yield, or you could buy the weed-outs with hFE<50 for a dollar a bucket. (Even before that, CK722 "experimenter grade" was hFE of 10 or even 5.) There might be a borderline grade 40-80 at an inbetween price.
So many designers of that era targeted hFE near 50. Less made design awkward, higher cost more.
When higher hFE became common/cheap, there was more emphasis on circuit techniques which worked with "any" hFE. When my prof said "hFE>50", he meant he might check my design with hFE=5,000! Indeed it isn't that hard to keep things within reasonable limits with any hFE to infinity, though you do need to target a minimum hFE below which you don't expect the design to meet all specs.
So i have measured about half of these and they all sit, min 55, max 80. So they are useable. if your fussy about q2 / q3 being 90+ then i'd skip these.
But just a word of warning, i know some GE's are pretty tolerant to inserting the legs into a circuit incorrectly. These are not one of them! I've killed 6 of 40 so far, and im pretty sure now that its from the base or collector, brushing across the wrong socket as i put it into the leakage tester. Even a half sec touch -> transistor is now a diode. So if you buy some, yeah, be EXTRA RIDICULOUSLY careful. If you insert the legs incorrectly theres a good chance you'll kill it.
Paul
Quote from: IvIark on November 08, 2012, 03:24:15 AM
I got two lots of 50 x GT308V's and measured them all with my Peak and this is the spread I got:
I got these a couple of years ago and have heard a lot of people getting much lower gain batches since.
these sound too low, I bought 50 recently and majority was around 90.
Does anyone know, when people say something like "for a fuzz face Q1 is best about 70-90, Q2 100-130" what collector current they are measuring it at? Or base current will do, as it's easier to fix.
Quote from: Kesh on November 12, 2012, 08:38:28 AM
Does anyone know, when people say something like "for a fuzz face Q1 is best about 70-90, Q2 100-130" what collector current they are measuring it at? Or base current will do, as it's easier to fix.
Yeah thats the question isnt it. As PRR described above, the HFE can change with collector current. (I was going to start a new topic about this actually but it seems approperiate here):
Which makes me steer even more towards the conclusion that HFE can mean jack squat with fuzz's, (within reason of course). 70-90, should be redefined as 50 - 200. Seriously, anything in that range sounds good to my ear. Sure you get a bit of extra sustain over 100, but they all still sound 'good'. Some low gainers i've found to sound better in the 50-100 mark (the ones im currently selling in the trade section) then others ive had that sit perfectly in the 'recommeded' ranges.
Last night i was curious to see what the HFE's were of the transistor set i bought off small bear some time ago. To my surpirse they measured around 140 and 170 hfe. Leakage was around 300ua and 200ua. These dont sit within the 70-90 / 100-130 HFE range. I'm not saying he's transistors are no good. On the contrary, they sound awesome! But i think thats more to do with the actually brand (2n's) then the hfe's?
Prehaps im going to start a war with these comments, but you know. Thats what i do. I'm a practical learner. And from what i've actually
heard thus far, anything over 50, sounds good, with only subtle differences, all the way up to 200hfe. Even over 300ua leakage sounds good, again within reason. over 1000ua i can hear it starts to sound squishy. But i wouldnt be suprised if in a blind test some guitarists would actually perfer this sound.
So, either, im going deaf from sitting infront of my cranked up amp for too many hours (highly likely) or theres not quite as much importance on HFE as what has been recommended.
If this information is incorrect please educate me. I mean that seriously.
Paul