Please help with Axis Face?

Focalized · May 03, 2008, 10:27:52 PM

I used this layout.

http://www.aronnelson.com/gallery/main.php/v/jpm83s-Gallery/album176/Vero+layouts/Axis+face+rev_3+vero.gif.html?g2_imageViewsIndex=1

I put in 2n3904 transistors. I don't have the ones in the layout. For Q2 I crossed Collector and Base like in the layout. I've been playing around with the transistors all which way and once I got a slightly darker clean, unity to bypass sound. No fuzz, vulume and smooth controled level, gain did nothing. Mainly no sound as of now. Even with the ECB all correctly in place for Q1, 2.

I used a 25k trim pot. When I did have the clean sound it worked like a volume. I used a tantalum in the 15uf spot.

All pots are wired correctly.

Voltages:

Q1
C - .13
B - .68
E - 0

Q2
E - 7.3
C - 8.5
B - .13

The trim pot measures 8.7 on all legs at max. 8.5 when turned down. Basically what the battery reads. Is this where the problem could be? I think id get a bad distorted fuzz with volts that high at Q2. I'm new to debugging. This is the first pedal where I can't find the problem right away. Checks all the parts, checked the cuts on the board.

I'm still a little unsure about the transistors. I figured any NPN will work as long as I cross the C and B for Q2 like that layout says.

A couple pics that might not help:
http://www.artistserver.com/m1/89/76/media/25133.jpg
http://www.artistserver.com/m1/89/76/media/25134.jpg

Focalized · May 03, 2008, 10:45:40 PM

Oh and now i just found that The guitar signal passes in bypass and when engaged with the battery disconnected. That's not normal is it?
Could this just be a bad switch? Still voltages are weird.

sfx1999 · May 04, 2008, 12:58:24 AM

Sounds like you wired your switch incorrectly.

Focalized · May 04, 2008, 01:09:58 AM

Quote from: sfx1999 on May 04, 2008, 12:58:24 AM
Sounds like you wired your switch incorrectly.

No it's wired like all the pedals i've done. You can see the output from the level pot.
http://www.artistserver.com/m1/89/76/media/25135.jpg

When activated, and without power, the signal goes through but looses some high-end. I don't get this.

ambulancevoice · May 04, 2008, 01:31:04 AM

did you insulate the bottom of the board?

Focalized · May 04, 2008, 01:48:59 AM

OHHH! i found an issue. My baad. Should have worked with it more. Just need to move the electros a bit.

This was a not needed post. But thanks for looking.

Focalized · May 04, 2008, 02:32:56 AM

Well I got it working i think.
The gain is pretty low. Even with 2N5089 transistors. Attack on max squeals. Smooth control seems like a gain control.
Q2 collector at 4.58
What's this supposed to sound like? I've about read a lot of people loving it.
That layout is verified, right?

ambulancevoice · May 04, 2008, 03:00:13 AM

well, its supposed to sound very close to a germanium fuzz face minus the instability of the the germanium transistors

sfx1999 · May 04, 2008, 02:53:37 PM

Are you sure you used the correct value for C6? It looks a little small to be 15 uF. That could cause a problem. Another possibility is that the attack is not connected correctly.

You might also want to try replacing some transistors,

Focalized · May 04, 2008, 05:06:40 PM

You know the tantalum might be the problem. It says u15 on it. I thought that meant 15uf. I got it from a BYOC TS-808 Kit. I looked at the kit instructions and saw it's actually .15. Should have checked that first. I don't have the right 15uf now but I'll try a 10uf and a 22uf to see how they work out,

Really glad you said something about that cap! Thanks!

sfx1999 · May 04, 2008, 07:29:27 PM

Either one of those values would work fine. You don't really need to obtain the exact value. Not having the correct capacitor there can reduce the gain of Q2 significantly.

Focalized · May 04, 2008, 08:33:15 PM

Yeah I got it working nicely. I used the 22uf. It sounds pretty good. Musical and crunchy with the fuzz. A little harsh with single coils. I haven't tried various transistors yet. Since I have to cross the legs and i didn't feel like doing that now. Just have a BC108 and a 2N5089.

ambulancevoice · May 04, 2008, 08:51:39 PM

Quote from: Focalized on May 04, 2008, 08:33:15 PM
Yeah I got it working nicely. I used the 22uf. It sounds pretty good. Musical and crunchy with the fuzz. A little harsh with single coils. I haven't tried various transistors yet. Since I have to cross the legs and i didn't feel like doing that now. Just have a BC108 and a 2N5089.

you need lower gain transistors
too high gain will make the fuzz harsh
try get transistors with hfe's close the original transistors used in this pedal

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Please help with Axis Face?