GT313A Russian Ge transistor for a Rangemaster?

svstee · April 07, 2009, 10:06:57 PM

I've heard of people doing this, but I'm a little shaky on how the Rangemaster works anyways, and the weird pinout (BCE) and internal shunt between base and emmiter, and I don't really know where to start. Can I just drop it in to a Rangemaster schematic and fix the orientation or do I need to maybe use a trimmer to tweak bias?

Thanks!

brett · April 08, 2009, 03:03:46 AM

Hi
just drop it in.
There's no internal resistor in a GT313. Maybe on other Russian devices?
IIRC MartyMart likes his FuzzFace built with GT313s.
cheers

anchovie · April 08, 2009, 03:10:04 AM

I've used the GT311 which is the NPN version and that does have a shunt resistor. If the internal resistor is there it makes the hFe readings stupidly low on a multimeter that can measure transistor gain. When I built a Fuzz Face I tried out different bias resistors on the breadboard and ended up with 68k for Q1 rather than the original 33k, so I'd say use a trimmer or experiment before soldering. I think some people don't expect the resistors on old Ge schematics to be the "golden" values anyway.

danielzink · April 08, 2009, 07:11:45 AM

Great minds think alike.....I'm in the process of building a RangeBlaster right now - with GT313's.

I've also substituted them in a Buzzaround build and they sound fine.

Dan

svstee · April 08, 2009, 11:44:20 AM

danielzink, did you have to tweak resistor values? Also, forgive the newbhood, but what does the trimmer control?

svstee · April 08, 2009, 03:31:10 PM

OK, I was thinking about using this simple layout http://www.aronnelson.com/gallery/main.php/v/DRAGONFLY-LAYOUTS_0/album14/album150/RANGEMASTER_PERF_001.gif.html and just fixing the pinout, and maybe replacing the 3.9K resistor with a 5k trimpot. Good idea or not? I have seen so many different schematics and layouts for this circuit I just picked one that was already laid out and had a bit of room for tweaks.

anchovie · April 08, 2009, 03:40:50 PM

I wouldn't worry about the 5k trimpot for now, try the layout as-is with the 100k trimmer to set the bias. Andrew was even kind enough to say what voltage you're aiming for!

kurtlives · April 08, 2009, 04:01:27 PM

Quote from: svstee on April 08, 2009, 03:31:10 PM
OK, I was thinking about using this simple layout http://www.aronnelson.com/gallery/main.php/v/DRAGONFLY-LAYOUTS_0/album14/album150/RANGEMASTER_PERF_001.gif.html and just fixing the pinout, and maybe replacing the 3.9K resistor with a 5k trimpot. Good idea or not? I have seen so many different schematics and layouts for this circuit I just picked one that was already laid out and had a bit of room for tweaks.

That layout already has a trimmer for biasing on it.

Stock there is a resistor from V- to base. Then a resistor from base to ground. This forms a voltage divider, the Vref is set at the base.

The 100K trimmer replaces the resistor going from base to ground. This lets you dial in just the right base voltage. Then you can get your transistor to bias up.

The 3K9 resistor does affect bias but you don't alter that value generally when biasing. Decreasing its value will increase gain and vice versa.

svstee · April 08, 2009, 04:18:13 PM

Ah, OK. Thanks for all the patience, guys. One more thing, I assume this circuit is negative ground, do I need to do anything special with that besides just running + to ground and - to 9v in?

anchovie · April 08, 2009, 04:31:46 PM

The circuit is positive ground, it specifies a PNP transistor and has the + terminals of the electrolytics going to the ground point.

svstee · April 08, 2009, 04:33:00 PM

Yeah, thats what I meant, my fingers and my brain are on different pages.

kurtlives · April 08, 2009, 05:26:46 PM

If all electro caps have + towards ground, 9V+ is grounded and your using a PNP transistor you set.

svstee · April 08, 2009, 06:12:37 PM

Cool, thanks!

IvIark · April 11, 2009, 08:17:16 AM

Quote from: brett on April 08, 2009, 03:03:46 AM
There's no internal resistor in a GT313. Maybe on other Russian devices?

There's shunt resistors in my GT313A's between base and emitter, confirmed by a Peak Analyzer. Having said that they still work fine in a Rangemaster

danielzink · May 01, 2009, 12:03:20 AM

Hey All,

Got my (GT313)Rangemaster built tonight and have a problem.....

very, very, very low output out of the circuit. volatges on all three pins are in the 2.0 + - volt range.

I dropped in a (fake)NKT275 and it jumped to life - also the bias jumped up into the 5 volt range.... odd?

Dan

svstee · May 01, 2009, 12:31:43 AM

I built one and it sounded good, but the whole negative ground thing has kept it off my board. I need to stop being lazy and build a polarity inverter.

danielzink, have you only tried it with one GT313 transistor? You might just have a dud. I haven't had a bad one yet, but I've only used like 3...

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GT313A Russian Ge transistor for a Rangemaster?