ToneBender debug

[andershp]

Hello

This is the second time I try building this, since I made an opvious mistake the first time.  Help debuggin this will be very much appreciated.

Name: Vox Tone Bender
Source: http://www.aronnelson.com/gallery/main.php/v/Richard-Boop-RLBJR65/album84/VoxToneBender.gif.html

I've followed the layout closely, but made the following changes since I tried this layout (http://fuzzcentral.ssguitar.com/voxbender/voxtonebenderschematic.gif, which worked on the breadboard, so I decided to use that circuit again the second time:
C1: 0.15uF instead of 0.22uF
C2: 4.7nF instead of 0.033uF
C3: 15uF instead of 25uF
P1: 50KA instead of 500KA

I'm using AC128 transistors with 81-90 hfe for Q1 and 111-120 hfe for Q2, but these worked the first time I tested it on a breadboard as well.
I also found a datasheet for the AC128 transistor and, as far as I know, located the right  pins on it.

The circuit is positive ground and the transistors are PNP as well - I haven't made the offboard connections yet, but I'm going to make it positive ground, input grounded also, so nothing is hacked or anything.

I've tryind it out with both a battery and a power supply, but both gives the same result.

It doesn't make any sound, however if I place a finger on the stripboard between the wires for the potmeters and the R6 resistor (which is possibly on my layout since my stripboard is a little wider), it does make a somewhat right sound. I've tested the connectivety of the wires between the pots and the board, but they are fine. (I know this seems unlogical)

Q1
C= -7.5 V
B= -0.07 V
E= 0  (?)

Q2
C= -9.1 V
B= -7.25 V
E= -7.33 V

Thanks

Anders H

[Govmnt_Lacky]

Q2 Collector is definitely wrong. That should be around 1/2 of the input voltage and it looks like you have ALL of the input voltage going there 

Check connections between input power (-9V) and Q2 collector.

Good Luck 

[andershp]

The voltage between the input and the Q2 collector is around 0,6 V, however the measurements change a bit, so I'm not sure how exact this is.

Shouldn't the Q1 Base and Emitter have some different values as well - or is that beacause of the high voltage on the Q2?

[Govmnt_Lacky]

The voltage between the input and the Q2 collector is around 0,6 V...

To have the circuit operate properly, the Q2 transistor needs to be biased properly. This is done by adjusting you resistance value on the Collector (8K2) to get 1/2 of your input voltage. If you are inputting -9V into the circuit, then you should adjust that resistance value until you get -4.5V on Q2 collector. That is why people usually install a 20-25K trimmer pot instead of the fixed 8K2 resistor.

Shouldn't the Q1 Base and Emitter have some different values as well - or is that beacause of the high voltage on the Q2?

This is possible. I would have to research the voltages on some working units.... but I think I should leave that to you 

If I were you, I would triple check ALL of my component values, resistor values, and orientations (especially electro caps). Then, check for solder mistakes.

Good Luck 

P.S. You SHOULD have the exact same voltage on Q1 Collector and Q2 Base. You seem to have a little bit of a difference on that as well.

[LucifersTrip]

Q1
C= -7.5 V
B= -0.07 V
E= 0  (?)

C is too high and E is correct (remember, it's grounded)

Q2
C= -9.1 V
B= -7.25 V
E= -7.33 V

These are way off, which would suggest a mis-wiring or bad connection.

Is it possible that you can give a clear closeup pic of the circuit so someone can find a possible error?

Btw, I just finished a germanium Fuzz Face variant (Super Beatle). I wrote the voltages on the schematic so you can get some idea of what you're after.

http://www.luciferstrip.com/fuzz/vox-superbeatle-distortion-ge.jpg

btw, I built from the exact schematic you used and it sounds great. very thin fuzz due to the .0047Uf

[andershp]

I will post close up pictures of both sides of the board tomorrow, but I don't have time right now.

Okay thanks, I'll have a look at it.

Btw, nice song and video for "Lucifer Says Die"! 
May I ask how you learned to make those video effects?

[LucifersTrip]

I will post close up pictures of both sides of the board tomorrow, but I don't have time right now.

sounds cool...hopefully someone'll be able to help. I'll even try to remember to dig out mine to check the actual voltages.

Btw, nice song and video for "Lucifer Says Die"! 
May I ask how you learned to make those video effects?

thanx ...tho, I didn't do any effects. it's actually deleted scenes from one of my favorite 1960's drug movies, "Mantis in Lace" (A topless dancer attracts, seduces, then murders the men she sleeps with while flipping out on LSD)

I just did a ton of editing

[andershp]

By andershp at 2011-09-15


By andershp at 2011-09-15

Okay cool - I think I'm going to have a look on that movie then   but nice however.

I hope anyone is able to help on this.

Btw, the white wires goes to the pots, the green is the input, the black is 9V- and the red one is positive ground. As seen on the schematic, the output is on the middle lug of P1.

[LucifersTrip]

man, I'm the wrong person to help with vero. I've built a million fuzzes, but never on vero.

on a quick look, clarify 2 things...first, did u leave out R5 since you're building the schematic version?
http://fuzzcentral.ssguitar.com/voxbender/voxtonebenderschematic.gif

and second, are you sure Q2 is oriented correctly?  in your pic, it looks like the tab (emitter) is up, but the collector is supposed to be connected to R3

[Electric Warrior]

+1 on Q2 orientation.
Also, bending leads in the direction of other strips is a bad idea. You might have shorted out several of them.

Here's what a nice vero board job can look like:

[andershp]

on a quick look, clarify 2 things...first, did u leave out R5 since you're building the schematic version?
http://fuzzcentral.ssguitar.com/voxbender/voxtonebenderschematic.gif

and second, are you sure Q2 is oriented correctly?  in your pic, it looks like the tab (emitter) is up, but the collector is supposed to be connected to R3

Yes I did leave the R5 out, since I had already tested the circuit in the link.

You are right, but I think that may be because I tried a different orientation, since I wasn't totally sure if it was right - I might have forgot to change it back??

However !  - I have discovered the error: I forgot to add the wire between row 5 and 7.  Pretty stupid mistake, but now it works.

Thanks for the help anyway - I appreciate it