Russian GT108V, GT313A

[seedlings]

Admittedly, I'm cheap.  While I'd like to spend $30 on a couple of tested Ges to see if I like how they sound, instead, for half the price I bought a pile of these GT108V and GT313A specimens.  I'm liking 2N2222 and even 2N3904 for cheap fuzz, but wanted to try the real germanium experience- hopefully a few of these may fit the bill.  I did a little research here and these may not be all bad.  The GT108V have a 10V rating though- should I take any extra caution with 9V wall warts?

CHAD

[seedlings]

Got these in and had some time to test in Keen's Transistor Tester circuit.  Through the first 25 GT108V:
Gain-QTY
50s - 1
60s - 3
70s - 1
80s - 4
90s - 2
100s- 3
110s- 6
120s- 2
130s- 1
150s- 1
And one keeps reading a gain of 200~205. Most had leakage under 100uA, with a few in the 150-180 range.  Sound darn nice to my ear.

Haven't tested any Gt313 yet.

CHAD

[kupervaser]

GT313 are good. I have a lot. Most of them are HFE 40-50 and 0 leekage.
Sounded very good in fuzz face, although I really can't hear the differences in sound between different transistor manufacturers.

[seedlings]

GT313 are good. I have a lot. Most of them are HFE 40-50 and 0 leekage.
Sounded very good in fuzz face, although I really can't hear the differences in sound between different transistor manufacturers.

What is the pin connected to the shield on the GT313?  I get the Emitter, Collector and Base, but can't decipher what that shield pin is.

I had to read and re-read the testing instructions because I kept getting such low leakage there must have been a mistake, but the leakage was in the tens of microamps on most of them.  My resistors were very close 2466K and 2.204M and the battery was 8.97V.

Also, regarding testing transistors, when battery is first applied the voltage may start at 150mV then slowly creep down.  Similarly, when the 2M2 is grounded the voltage starts at .110 then creeps down after several seconds.  If this is normal, will the initial voltage reading be accurate or the reading after 10 seconds or so?

CHAD

[fpaul]

The fourth pin is to ground the shield for lower noise.  I have some gt308s and they were all very low leakage.  Great in fuzzface and rangemaster but the tonebender I made was one of my few diy dissappointments.  Later on I read somewhere that Q3 needs to leak a little.

[seedlings]

Here are the full results
GT108V
Gain-QTY
50s-1
60s-6
70s-4
80s-8
90s-7
100s-6
110s-10
120s-3
130s-1
140s-1
150s-2
180s-1 (this is the one that read a higher gain sometimes)

GT313A
40s-2
50s-3
60s-1
70s-1
90s-1
120s-1
130s-1
140s-2
160s-1
230s-1
240s-1
280s-1
300s-1
350s-2
360s-1

The GT313As were all over the place (hfe rated 20-200) but had virtually zero leakage.

In hindsight, the GT313As weren't needed, but I wanted to 'diversify' since the cost was so low.
CHAD

[zombiwoof]

Dunlop is using Russian germaniums in the recent Joe Bonamassa Fuzz Face, does anyone know what they are using?.

Al

[sgmezei]

+1
I also would like to know what they are using in the Bonamassa FF.
Does anyone know what they are using in the Eric Johnson FF?

[rousejeremy]

The EJ is likely BC183L

[brett]

Hi

I kept getting such low leakage there must have been a mistake

That's normal. Leaky, noisey, heat and current-sensitive (and otherwise dodgy) British/US/etc Ge devices from the 1960s and early 70s don't compare at all with Japanese and Russian devices produced in the late 70s and 1980s.  The latter are virtually leak-free and very quite.  I have tested and used many GT313b, and found them to be excellent. The only "catch" that I have found is that a significant proportion (~30%) have too low a hFE (less than 50) for most circuits.

cheers

[PRR]

> Leaky, noisey, heat and current-sensitive (and otherwise dodgy) British/US/etc Ge devices from the 1960s and early 70s don't compare at all with Japanese and Russian devices produced in the late 70s and 1980s.

Yup. 1950s Germanium was extracted from coal ash. They didn't fully understand how pure a good semiconductor needs to be. They didn't have the processes to get high purity.

Silicon is tougher to purify but had many advantages. By 1972 Silicon purification was pretty mature. All the Big Boys rushed to Silicon production.

Meanwhile the secondary makers were using ideas from Silicon purification to improve Germanium purification for lowest-cost products that had no need for Silicon's advantages.

Germanium always leaks more than Silicon; however some of the high leakage of early devices probably was crappy Germanium and dirty surfaces more than the intrinsic semiconductor.

[seedlings]

When testing in the Keen test circuit- press the button for gain and the value shows up, then starts to change after a second.  What value is correct, the initial push of the button, or the one after a few seconds?

As an example, press the button, get a reading of 250, then after less than a second it drops to 110, then slowly falls (usually) or rises (occasionally) as the seconds tick by with the button pushed.  Is the gain 250, or 110 (after one second), or 102 (the value after 5 seconds)?

I record the value after a couple of seconds.

CHAD

[Ripdivot]

When testing in the Keen test circuit- press the button for gain and the value shows up, then starts to change after a second.  What value is correct, the initial push of the button, or the one after a few seconds?

As an example, press the button, get a reading of 250, then after less than a second it drops to 110, then slowly falls (usually) or rises (occasionally) as the seconds tick by with the button pushed.  Is the gain 250, or 110 (after one second), or 102 (the value after 5 seconds)?

I record the value after a couple of seconds.

CHAD

I wait for the number to stabilize and that is my reading...

[seedlings]

When testing in the Keen test circuit- press the button for gain and the value shows up, then starts to change after a second.  What value is correct, the initial push of the button, or the one after a few seconds?

As an example, press the button, get a reading of 250, then after less than a second it drops to 110, then slowly falls (usually) or rises (occasionally) as the seconds tick by with the button pushed.  Is the gain 250, or 110 (after one second), or 102 (the value after 5 seconds)?

I record the value after a couple of seconds.

CHAD

I wait for the number to stabilize and that is my reading...

Thanks!

CHAD

[A.Gillies]

I've used GT108V's in a few fuzzes and they work great and sound awesome.

[seedlings]

I've used GT108V's in a few fuzzes and they work great and sound awesome.

Honestly I'm having trouble finding a bad combination up to about 120 gain.  Two 50s sound good.  A 40 and a 100 sounds good.  An 80 and a 120 sounds good.  Past 120 they can get 'blatty' but even that seems fixable with bias.

CHAD

[kevinlipe]

I just got my hands on a box of 100 MP42B's, also Russian Ge's. The (Russian) data sheet says the hFE range is 45-100, so assuming that's even close to accurate I should find some that sound great. These MP42B's are lacking the fourth shield pin that the GT's seem to have, but they still have that "alien spaceship" look.

I also, on a whim, bought a lot of 200 KT315 silicon transistors, that look like little red-orange plastic rectangles. I have no idea what to expect out of these, and know nothing about them other than they're NPN silicon and they look cool. I plan on throwing them on the breadboard this weekend and seeing what happens.

I'll report back after I get some time to play with them. I'm planning on trying some Maestro/Tone Bender stuff with the MP42's, but if those circuits are dependent on leakage in Q3, maybe I'd be better off going in the Fuzz Face direction.

[LucifersTrip]

I've used GT108V's in a few fuzzes and they work great and sound awesome.

I've used em in a bunch. Since they have extremely low leakage, they're great for a darlington pair in a Buzzaround or MKIII.

Though, I have found that for a Fuzz Face or variant, they're excellent for Q1, but don't give you that soft mushy fuzz that a Jap, UK or US transistors can give you for Q2.

They're also very cool for a Rangemaster (since low leakage is also a plus) and a Fuzz Rite or variant since you're not looking for a soft mushy fuzz there...

[StarGeezers]

 Seed , that's pretty Cool !!!    Gives one a new found faith on trying some Ge circuits ...   

[seedlings]

Seed , that's pretty Cool !!!    Gives one a new found faith on trying some Ge circuits ...   

As long as it doesn't drive up prices 

CHAD