Germanium Transistors with Shunt Resistor HFE measuring

[chromesphere]

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

[Kesh]

what type of transistor? and what hfe are you getting? and are you somewhere cold

[chromesphere]

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

[Kesh]

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.

[Chugs]

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.

[LucifersTrip]

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!

[chromesphere]

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

[LucifersTrip]

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.

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.

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:

[chromesphere]

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

[LucifersTrip]

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

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

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?

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

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

[chromesphere]

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

[LucifersTrip]

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

[chromesphere]

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

[PRR]

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.

[chromesphere]

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

[LucifersTrip]

without a data sheet or Peak Atlas, how do you determine if a transistor has a resistor shunt?

[chromesphere]

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

[IvIark]

I got two lots of 50 x GT308V's and measured them all with my Peak and this is the spread I got:

Code Select Expand


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.

[chromesphere]

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

[IvIark]

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.