Ampeg Scrambler not working, contains full debugging info

[glops]

Nice to hear, I'm on bread boarding my scrambler for the 5th time and it still doesn't work.   It's probably something simple but it's really the one effect that I have always wanted to build so I need to get through it without put the parts back in the Scrambler plastic baggie.

[ebuprofen]

Hey, guys!
I have a problem with my scrambler
Buld it from original schematic and my own layout, checked the schematic and the layout, no problem.
Ow, thae problem is that it's not high gain, it sound more like overdrive and octave is barely noticible.
I used Fairchild 2N5308 and 2N3904, could it be that these Fairchild transistors are somehow low gain?
Tha unit works, but the sound is not what it should be.

[glops]

I used 5306 which I think has the same hfe and pinout as the 5308.  Make sure you have the transistors oriented correctly in the layout.  It's not the EBC as the 3904, usually it's ECB for Q1, 2, 3.

[ebuprofen]

checked that, everything should be ok.

Central 2N5306 are very bright, almost piercing, and have tons of gain, which is nice with a strat. Fairchild 2N5306 were nice a bit darker, pretty low gain, though.

this is a quote from tonepad build reports, perhaps I need to use some other transistors?

[Solidhex]

Q2 is the transistor that's responsible for the sort of distortion type tone in the circuit. Q1 is a buffer, Q3 and 4 generate the octave with the diodes.

[glops]

Good luck with the project.  I perfed this one a couple of weeks ago.  It took me mulitiple tries on a breadboard to get it to work and finally got it.  It's really fun to run other pedals into it adjusting the blend.

[ebuprofen]

ok, I will get back home tomorrow and try to swap Q2, but I have barely noticeable octave, does that mean my 2N5308 doesn't work right?

glops, what problems did you have?

[glops]

I basically tried to build it on a breadboard 4-6 times and could never get it to work. I think the last time I left out the 3 diodes that were not included in the originals as marked per the schematic.  Got it to work and then put those diodes back in.  The whole middle section with the diodes is just confusing.  Do you have this soldered to a board?  Have you checked voltages on each transistor pin.  I remember not getting good voltage readings on Q2 but I just didn't have it pieced together right.  Double check the voltages on the pins and then make sure each resistor's value is correct according to your layout.  If you have the transistors oriented correctly according to their pinout you probably made a simple mistake somewhere along the line....

[ebuprofen]

Q1
C =9.25v
B =4.39v
E =3.48v

Q2
C =3.35v
B =0.95v
E =0.28v

Q3
C =9.25v
B =4.57v
E =3.53v

Q4
C =8.92v
B =4.47v
E =3.53v

D1
A (anode, the non-band end) =4.48v
K (cathode, the banded end) =4.57v

D2
A (anode, the non-band end) =4.56v
K (cathode, the banded end) =4.46v

that's what I've got

and the schematic
original http://www.experimentalistsanonymous.com/diy/Schematics/Fuzz%20and%20Fuzzy%20Noisemakers/Ampeg%20Scrambler.gif
my http://img217.imageshack.us/i/schem.png/
layout http://img339.imageshack.us/i/layoutmf.png/

I also noticed that I put 100nF input cap instead of 10n (I don't know why ) and 10uF instead of C6, wich should be 4u7

[oldrocker]

The Scrambler should have a dirty octave not that subtle.  Try MPS darlington transistor types if possible for good results.  No it's not high gain and maybe not at unity volume.  But when it's working you'll know it without a doubt.  Turning the blend pot should go from an overdrive to sick sounding high octave mayhem.

[glops]

Do a search here for Scrambler threads, you will find one that has voltage readings.  I remember that I compared mine to those of a working Scrambler and when mine started working, my voltages seem to match.

Make sure your caps are oriented the right way and check your wiring for the blend pot.  You will know when this thing is alive.   Do you have this on bread board, soldered to perf, soldered to a GGG board?  Did you make sure your off board wiring is correct (switch, jacks, etc)?   

I poured over all of the Scrambler threads on this forum.  Don't know how I got mine to work but was glad when it did.  It was just annoying.  Now that its done.  I like it, but don't love it.  I was obsessed to get this particular circuit in a box but as a standalone, I am less impressed.  But I have found that running other things into it and using the blend as a mixer there's a lot of great and varied sounds you can get.  I wish you the best of luck.

[ebuprofen]

The thing is, that it works, but I have no octave and it's more like overdrive, than insane distortion, Blend work too, Texture seems to do nothing.
I've checked the board several times, it look right to me. I ran out of ideas, except changing the transistors. The voltages almost match the ones in the first post of this thread.

[ebuprofen]

ok, watched some videos, some guys have insane fuzz, some not so insane.
in my case it's not that insane, but when I replaced the 8k2 to 300k i sounded like it should, but octave doesn't work, texture pot doesn't change anything.

[glops]

double check everything around the texture pot. On mine, when that control is turned up, I get the octave fun.  Try different transistors for Q2.  Don't give up!

[ebuprofen]

But why Q2? Does it affect the octave? It seems to me like the Q3 and Q4 doesn't do anything. I've checked the board like 2348932648724 times and haven't got any clue what's wrong.
Going to order 2N5306 and MPSA14 and one 2N5089, as well as the 1N456 diodes and try with them.

[glops]

I say check Q2 only because if you are using a 3904, the transistor pinout is different from the 5308 (Q1,3,4) you are using.  I looked at the data sheet for the 5308 and it seemed to be the same as the 5306 in terms of the pinout and the hfe. 

May be good to post your layout here next.  Although, you checked it - maybe you're missing something.  I think my biggest problem was in the assembly.  After Q2 and around the texture control it got confusing just building it on bread board for me. Does it pass clean signal when disengaged?  Have you had success with other pedals? 

[ebuprofen]

Q1
C =9.25v
B =4.39v
E =3.48v

Q2
C =3.35v
B =0.95v
E =0.28v

Q3
C =9.25v
B =4.57v
E =3.53v

Q4
C =8.92v
B =4.47v
E =3.53v

D1
A (anode, the non-band end) =4.48v
K (cathode, the banded end) =4.57v

D2
A (anode, the non-band end) =4.56v
K (cathode, the banded end) =4.46v

that's what I've got

and the schematic
original http://www.experimentalistsanonymous.com/diy/Schematics/Fuzz%20and%20Fuzzy%20Noisemakers/Ampeg%20Scrambler.gif
my http://img217.imageshack.us/i/schem.png/
layout http://img339.imageshack.us/i/layoutmf.png/

I also noticed that I put 100nF input cap instead of 10n (I don't know why ) and 10uF instead of C6, wich should be 4u7

here are my schematic and layout, it's wired without switch in test box http://yfrog.com/4rp1040640j
tested with several 2N3904 and flipped them 180, no luck.
this is not my forst project http://ebupro.blogspot.com/

I'm confused, simple effect, but it's not working correctly.
I would be very thankful if someone check my layout and the schematic.

[ebuprofen]

Found mistake in my schematic, the output capacitor was connected do the base of Q4 not collector, a redrew the schematic wrong, so as the layout, going to test it today