Want a FuzzFace pcb layout for Russian GT311 transistors?

[Skreddy]

I've made a layout, but it's not built yet, so it's not verified.  What I've seen and heard in testing these transistors so far is that they drift a lot less due to temperature than most other metal-case germaniums and the ground lead really cuts out the hiss.  So it promises to be a cool little circuit, having the pad for that case lead to go to ground (and of course the leads lined up as per its unusual pinout).

Sorry for the teaser; I will post the layout once I've built it and verified that it's good--that is if there's anybody out there with these transistors who wants it.

[$uperpuma]

post eet!

thanks!

[ambulancevoice]

+1

[bluesdevil]

Curious to see what values you used since I haven't had any lucking getting them to bias in a Fuzz Face circuit.

[Skreddy]

You know what?  I held off posting the layout 'till after I built it so as not to send anybody on a dead-end trip.  The damn thing doesn't work.  I used the pinout info others here have posted to create a custom part in Eagle PCB.  Simple enough circuit; doesn't work.  Don't have time to mess with it right now, so sorry.  I could post what I have, but it wouldn't do you a bunch of good.

[frankclarke]

I expect any Fuzz Face layout would work with Russian transistors. So try a working layount online perhaps.

[$uperpuma]

hmm... have you seen this datasheet, marc? might help. http://www.evita.lt/getPdf.php?id=8659

[8mileshigh]

I have the GT313B that I can't get to work in a circuit either, don't know what to do with them. 

Chris

[Skreddy]

Okay; take a look at this, imagining you're seeing the parts on the topside and the copper's just barely showing through the translucent board from the other side; see if my pinout is wrong...

(Board-mounted pots go on the copper side)
Really, these transistors have such low Hfe that I don't think I really have a use for them.

[puretube]

If this is a bottomviev pinout,
your componentview layout has Base/Emitter swapped...

[Skreddy]

If this is a bottomviev pinout,
your componentview layout has Base/Emitter swapped...

Thanks!  I no speakie the Russian.  So a mirror of the layout might work.  I've already tried this one with the transistors in backwards (the case lead left hanging) and still nothing, though.  Maybe the reverse-voltage of using them backwards the first time killed them?  Gah.  I'll try some "fresh" ones and see.  Hate these things now. 

[brett]

Hi
MartyMart wrote:

Looking down on the top surface with "case" lug towards you pinout is

E C B
   G  ----> case pin

So the layout seems fine to me.
Try a 25k trimpot wired as a variable resistor for biasing instead of the 8.2k fixed resistor.  Fixed resistors rarely work.
cheers

[dxm1]

If this is a bottomviev pinout,
your componentview layout has Base/Emitter swapped...

If that PDF is like the one for the GT308, it is a _top_ view. Kinda an X-ray thang. I had to use a DMM to get it right...   

[anchovie]

MartyMart's pinout was for a pnp device. I posted a verified pinout for the GT311J in another thread:

http://www.diystompboxes.com/smfforum/index.php?topic=61655.msg484572#msg484572

I've built a tonebender with these parts so I can confirm that it is correct.

[Dragonfly]

was it the 311 that had an internal resistor,making it need different biasing ?

[anchovie]

I used trimpots for biasing and it's all boxed up now, so I couldn't tell you how different the resistance was from using other transistors.

[Skreddy]

MartyMart's pinout was for a pnp device. I posted a verified pinout for the GT311J in another thread:

http://www.diystompboxes.com/smfforum/index.php?topic=61655.msg484572#msg484572

I've built a tonebender with these parts so I can confirm that it is correct.

I've got some GT311J which I'm very happy with.

Looking at the underside, the pinout is:-


          . B

          . C          . case

          . E

Which would mean that my layout is indeed incorrectly mirrored, if that's looking from the underside and not from the top.

So my problem, even though I try plugging them backwards, is that I'm using classic Fuzzface bias values instead of a trimpot.  And you say that these transistors have an internal resistor which makes them appear to be of lower Hfe than they actually are.  So maybe it would be worth it for me to whip up a new layout and slap a trimpot on it.  Or maybe I'll just wire up a pot temporary-like and find a good fixed resistor value.  Assuming they'd all need a bit of a tweak, a trimpot would be better.  Thanks!  Talk to you soon.

[bluesdevil]

Skreddy, I hope you hang in there with it. Thanks for posting back.

[brett]

Hi
apologies for mixing up the device type in the pinout discussion.
Did anyone notice that the (strangely) low hFEs measured for these devices is what you'd expect if there's internal resistance(s).  A small emitter resistor (a couple of hundred ohms) might explain hFEs of 20 indicated on a DMM for a BJT with hFE of 100 or more.
cheers

[Dragonfly]

Hi
apologies for mixing up the device type in the pinout discussion.
Did anyone notice that the (strangely) low hFEs measured for these devices is what you'd expect if there's internal resistance(s).  A small emitter resistor (a couple of hundred ohms) might explain hFEs of 20 indicated on a DMM for a BJT with hFE of 100 or more.
cheers

yep, thats why i mentioned the internal resistor thing....iirc, some people in the past were having real issues with biasing till they figured that out. i;'m not 100% sure it was the 311's, but i believe it was.