Russian SI transistors for dummies

[Halkbi]

I've been on the lookout for low gain silicon trannies lately, and I thought I might try an effort to collect some info on russian ones since they aren't nearly as well documented as their germanium counterparts. For me personally, I'm mostly interested in devices with a gain range of 70-120 hfe (since that seems hard to come by in new transistors) but any light that can be shed and collected into one thread will probably be helpful to a lot of people.

Personally I took a gamble on 50 KT801Bs a couple of months ago. The bulk I got ranged from 20-100 with the vast majority of them being in the 40-50 range, some in the 50-70 and a few in the end ranges (20-30 and 90-100). They are also very big and bulky. Slighly underwhelming, but I'm curious to see how they perform in a Fuzzrite.

Please share your experiences!

[antonis]

For me personally, I'm mostly interested in devices with a gain range of 70-120 hfe (since that seems hard to come by in new transistors)

I have nothing against Russian BJTs but there are also many "other origin" Si transistors of particular gain of interest..

e.g. 2N3393 (TO-92), 2N4401 (TO-92), 2N5550/51 (TO-92), BC141-16 (TO-39), BC337/338-16 (TO-92), BD135/137/139 (TO-126), BD239C (TO-220), KSC2073 (TO-220), TIP29 (TO-220), TIP31 (TO-220)

as well as most of medium power BJTs.. 

[iainpunk]

i'd recommend just using power transistors, like the BD139/BD140, they have low-ish gain in those ranges, but they take up a larger footprint for tight enclosures.

you can also use normal transistors in ''reverse Beta'', which decreases their gain anywhere from 5% to 95%, dependent on the internal architecture.
the 2n2222 decreases to 1/3rd of its Hfe, the BC547 to 1/10th, the BC139 keeps almost all its gain.
there are transistors that go down to an Hfe of 1, and lots of Ge transistors don't lose any gain.
experimentation is key, and measuring large batches of Hfe's and reverse Hfe's is a tedious but rewarding task, it helps in the future!

some transistors have odd behavior when reverse biased, like the 2N2222A. i can get it to work without any bias current, only a capacitor connected to the Base...

cheers, Iain

[mdcmdcmdc]

To the OP, fwiw, I've had good luck getting consistent NPNs in the ~80-110 range with 2n3903 and 2n3440. I don't think either are too difficult to find nor are they particularly expensive.

[andy-h-h]

I have a few KT315 transistors - they have an odd package with a BCE pinout, and flat pins.   BUT - they're also very cheap, work just fine and come in cool colours.  hfe is all over the place, so you do need to measure them.  The one's I have are low gain.  I built a modified BeeBaa with them, and it's a fuzz monster.     

[iainpunk]

and come in cool colours

do you have pictures?

i plan on nail-polishing the transistors with blacklight nail polish and use UV and yellow leds to illuminate them in my next fuzz build, and make them visible through a little window. inspired by the fuzz factory.

cheers, Iain

[andy-h-h]

and come in cool colours

do you have pictures?

i plan on nail-polishing the transistors with blacklight nail polish and use UV and yellow leds to illuminate them in my next fuzz build, and make them visible through a little window. inspired by the fuzz factory.

cheers, Iain

It’s a bit of a scrappy build, but you can just see the orange and yellow transistors.
 https://vero-p2p.blogspot.com/2020/07/roland-beebaa-modded.html

Scroll down to the bottom of the link above.   

[iainpunk]

and come in cool colours

do you have pictures?

i plan on nail-polishing the transistors with blacklight nail polish and use UV and yellow leds to illuminate them in my next fuzz build, and make them visible through a little window. inspired by the fuzz factory.

cheers, Iain

It’s a bit of a scrappy build, but you can just see the orange and yellow transistors.
 https://vero-p2p.blogspot.com/2020/07/roland-beebaa-modded.html

Scroll down to the bottom of the link above.

those transistors look so cool! i might order a bunch off of Ebay, and use them in the way described above, without the nail polish, since they already look cool!

cheers, Iain

[duck_arse]

pics of rusk transistors, of possible interest ......

https://www.diystompboxes.com/smfforum/index.php?topic=68976.msg701783#msg701783

https://zeptobars.com/en/read/kt315-kt361-bjt-npn-pnp

[duck_arse]

wouldn't it be good if someone built a green russian with yellow and orange russians?

[iainpunk]

wouldn't it be good if someone built a green russian with yellow and orange russians?

or with green 2SA1142 transistors, not russian, but green.
or a mix and match of the two options.

cheers, Iain

[bmsiddall]

Iain, I've used KT325 which I think were in the ballpark- used in si Mk1 & Mk2 tonebenders.  KT312V (100-200hfe), some KT3102 in your range.