Replacements - Octavia

[rasco22862]

Hi, im going to build de octavia from ggg. I couldnt get the :

1)2n5088
2)2n5087

Can i replace them??

Thanks a lot

[tcobretti]

Yes.  Any Medium to high HFE (500-800) transistor will work.  You could try 2N3904/2N3906, but they will have lower gain and it may gate the effect a little too much.

[rasco22862]

Yes.  Any Medium to high HFE (500-800) transistor will work.  You could try 2N3904/2N3906, but they will have lower gain and it may gate the effect a little too much.

1)2n3904 for the 2n5088 and 2n3906 for the 2n5087?? is this correct??
2)is there any better replacement??

[tcobretti]

What you need are med gain NPN and PNP NJT transistors.  There are certainly many options available to you.  I'd see what is available locally, and then look at their datasheets to see if they will work.

As long as you get one NPN and one PNP, odds are good they'll work.  In my Roger Mayer Octavia, which has some similarities to the Tychobrahe I think you are building, I used a Ge PNP transistor and it works great.

[rasco22862]

so any pnp and npn med to high gain (500-800hFe) transistor should work?

what NJT means??

[sfx1999]

You can sub those transistors you listed for them, but you won't have as much gain.

[tcobretti]

Oops, I meant BJT - Bipolar Junction Transistor.  A JFET won't work.

[rasco22862]

I get the transformer from 1k5 to 500 ohm, but there are 4 wires(2 and 2), and in the ggg layout there are 5 wires?? is it okay if i just wired only the four?

Thanks

[aron]

There is always the store link above. :-)

The 2N5089 will work fine.

[rasco22862]

Thanks i already get the transistors, i was asking about the transformer that has 4 leads, and not 5 like ggg

[rockgardenlove]

You'll need the center tap-the 5th wire.

[rasco22862]

What you mean center-tap the 5th wire.? I dont have 5 wires, i have 4, 2 for primary and 2 for secondary.

[rasco22862]

i mean , do i skip the fith wire?

[brett]

You could try 2N3904/2N3906, but they will have lower gain

but you won't have as much gain

Check out the schematic.
It is clear that the gain in an Octavia (as in many circuits) will be just the same.
The ratio of the collector AC resistance to the emitter AC resistance sets the gain of most common-emitter transistor stages.  That's why the emitter is sometimes bypassed by a capacitor (ie so that the AC resistance is low and the ratio and the gain is high).

So next time someone implies that hFE = gain, you can tell 'em to check the facts.
cheers

[rasco22862]

thanks for the reply!

but

I get the transformer from 1k5 to 500 ohm, but there are 4 wires(2 and 2), and in the ggg layout there are 5 wires?? is it okay if i just wired only the four?

Thanks

[rasco22862]

any reply?

[dxm1]

I get the transformer from 1k5 to 500 ohm, but there are 4 wires(2 and 2), and in the ggg layout there are 5 wires?? is it okay if i just wired only the four?

No.

i mean , do i skip the fith wire?

No.

any reply?

Get a transformer with a center tapped primary.

Or, if you're determined to try what you have, wire it up - just don't be too disappointed if it doesn't work.

[Pedal love]

Its a center tap that you need here. It divides the input signal into two equal output signals, of opposite phase to eachother.pl

[rasco22862]

so can i "fix" my 4 lead transformer??

[Pedal love]

You can't use it with only 4 leads. Go to General Guitar Gadgets...you'll have to do a net search. Then look for the schematics and layout for: Tycobrahe Octavia.
It has all the information on the proper transformers and orientations.pl