Super fuzz de-buggery!!

Started by MikeH, April 06, 2009, 11:06:11 PM

Previous topic - Next topic

MikeH

Quote from: R.G. on April 08, 2009, 07:31:03 PM
When you come back, you can ponder that bipolars also work "inverted", with the nominal emitter more positive than the base and the nominal collector more negative.
Originally, there was no difference between collector and emitter junctions. Later we found out that if you make the emitter junction really thin and small, it give more gain and higher breakdown voltage, so you can make the collector junction more burly. But they still show transistor action at below the emitter-base breakdown voltage, which is usually 6-10 volts depending on the device. Yours both have a "collector-base" voltage of less than 6V, so it's possible they work this way, albeit more poorly .

Ahhh...  Trickery.

So yeah, seems it was the pinout.  Although based on how I've got these things in here now, the pinout of these trannys is CEB.  Which is... well I've never seen that before.  And it's definitely different from the datasheet I found. 

So it works, what is the output supposed to be like on this guy?  I feel like its a little low; it still gets above unity, but only 5-10% of the upper level of the output is above unity.  Is that right?
"Sounds like a Fab Metal to me." -DougH

R.G.

Quote from: MikeH on April 08, 2009, 08:15:16 PM
So yeah, seems it was the pinout.  Although based on how I've got these things in here now, the pinout of these trannys is CEB.  Which is... well I've never seen that before.  And it's definitely different from the datasheet I found. 
You have them running inverted. I promise, the pinout is ECB, collector in the middle. Collector and base are swapped from the "USA" version of EBC like a 2N3904.

QuoteSo it works, what is the output supposed to be like on this guy?  I feel like its a little low; it still gets above unity, but only 5-10% of the upper level of the output is above unity.  Is that right?
Nope. It's got plenty of output. I suspect the low gain from inverted mode is getting you.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

MikeH

#22
Well... balls (to use the parlance of our times).

So if I'm running them inverted that means what I think is the collector is actually the emitter and vice-versa, right?

This is the only datasheet I can find:

http://pdf1.alldatasheet.com/datasheet-pdf/view/108447/ETC/2SC828.html

Originally I flipped pins 2 and 3 (C & B) but that led to my original problems.

edit: I just did some diagramatic doodling here, and I think this means I have the right legs bent around, but I just need to flip it around.
"Sounds like a Fab Metal to me." -DougH

R.G.

The datasheet is correct. When the legs are down and the flat face toward you, the pins are E, C, B from left to right.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

MikeH

I flipped them around, and yes, it has more output.  Funny, it sounds exactly the same, just louder.  Anyway, the saga comes to an end.  2 pages of debugging because I misread the pinout on the data sheet.  Even actually looking it up doesn't help sometimes.  Thanks for all of the help, it's been a great learning experience.  As they all should be.  :)
"Sounds like a Fab Metal to me." -DougH