Trouble with Ampeg Scrambler

[juancra]

Hi Guys!

I'd finished an Ampeg scrambler clone from tonepad, and I think that something is wrong. I can't get any distortion from it! it sounds just clean, perhaps a bit "hendrixean" at the final frets, but is not the hi gain monster that I listened in  Tonefrenzy sample . I've used 2n5306 trannys and 2n3904 instead of BC169 and 1N4148 diodes instead of 1N456, but all of them were listed in the proyect pdf as replacements. Does anyone have an idea of what may be wrong?

[$uperpuma]

there's a cap thats shown backwards on the layout... its lined out here...maybe that'll help... then go back and check all the normal things, solder bridges, etc...
http://fuzzcentral.ssguitar.com/scrambler.php

[tcobretti]

I memory serves, the pinout on the 5306 is weird, so I'd check that.  As well, the first transistor just acts as a buffer, so if you are hearing some sound, you might check the wires around the blend pot. 

BTW, I love the Scrambler.  It is certainly my favorite octave fuzz I have built so far - but I haven't built the Foxx Tone Machine yet.

[juancra]

I'd already checked the transistors pinout trying different combinations, 'cause i used sockets (I even turned it on without Q3 and Q4 and had the same clear signal). Tlcobretti, can you explain me more about the first transistor? perhaps that's the key

[tcobretti]

Notice that the signal comes off of the emitter of Q1 and goes to the blend pot and to the rest of the circuit.  So, when the blend pot is turned in one direction you just hear the buffer, and when in the other direction you hear the fuzz.  It sounds like maybe you're just hearing the buffer.  The way to really test it is to audio probe after the output cap.  If it doesn't work there, I'd audio probe backwards till I figured out where in the pedal the signal stops.  If you aren't familiar with an audio probe, here's RG Keen's design.

[Solidhex]

Hello

  I've had a similiar problem with my Scrambler from the Ustomp layout..  http://ustomp.com/?p=9  . All the controls seem to do what they're supposed to. The blend goes from a clean tone to the "distorted" side. The texture knob changes the character of the distorted side but in general its just not very distorted. There's some ring modulation present but this thing should be roaring. I have the Ampeg reissue version which is cool but a little on the muddy side. I was hoping a clone would get closer to that "Cactus" sound. I used NTE 519's for the diodes (1N4148/1N914) and BC5306's for Q1,3,4 and a 2N3904 for Q2. Everything is oriented correctly and I've payed close attention to the weird 5306 pinout.
My Voltages are:
Q1 e  3.17V   b 3.9V   c  8.45V
Q2 e  .24V     b .9V    c  3.33V
Q3 e  3.25V   b 4.1V   c  8.44V
Q4 e  3.24V   b 4.1V   c  8.1V
  This is with a 8.8V battery
  Does anyone notice anything strange? Could it be the diodes?

Thanks, Brad

[ustompsteve]

I just made another last week. Here are the voltages.

       E      B      C
Q1   3.38   4.32   9.08
Q2   .267   .935   3.35
Q3   3.42   4.48   9.07
Q4   3.41   4.48   8.70

It should roar. If it doesn't something is wrong. This effect is in no way subtle.

I used 2N5306's and a 2N3904

--steve

[Solidhex]

Hi Steve

   Any tips on what to listen for when I audio probe it? All my voltages look ok. Not sure what to look for to solve the problem.

thanks, Brad