Having a problem with a tonepad pcboard for the scrambler. I discovered the backwards cap on the dry side ofthe blend pot, which is wired correctly. I chucked the original cap out and replaced it the other way around.
I have a scope and I can see signal on both the base and emitter of Q4, but not the collector. So I'm looking at that output circuit over and over. Also, I don't see any signal at the base of Q2, but its there downstream. Changed Q2 - same thing.
I used 2n5306 s for Q1,3,4. They are from small bear. These are unusual to me in that the flat face (sort of a TO92 case) has no writing on it. The writing is on the round part. So which are you facing when they says he 5306 is "ECB" ?
Anyway, I look at them from the flat. Update: Steve just told me the ones he sold me are ECB. You look at the flat, like always. OK.
I have no effect sound, just clean, responding to the blend pot. I've searched the scrambler help threads and they sounded promising but those solutions turn out to not be my problem.
I started with a BC169b in Q2 (ECB as you look at the face) and the voltages seem a little odd. Now I've put a 5089 in its place (right?) and it is EBC as you look at the flat face.
Voltages: ( "E 3.6." Means emitter 3.6v. Typing on the phone) 9.7v supply.
Q1:E 3.6. C 9.5. B 4.5
Q2 (5089): E .3. B .9. C 2.3. (BC169B): E .2. C 4.6. B .8
Q3: E 3.8. C 9.7 B 4.7
Q4: E. 3.8. C 9.5. B 4.8
Tonepad pc board. Tonepad schematic
http://www.tonepad.com/getFile.asp?id=31 (http://www.tonepad.com/getFile.asp?id=31)
C3 is the cap that is wrong in the schem. I have the negative facing the output now.
Wait a minute... (It still doesn't work, mind you)- BUT those diodes that we supposed to be left out, according to tonepad, must be jumpered. Or that cap connects to nothing. Aw, no fair. Is this little guy the DIYSB snipe-hunt? Jumpers are in for D1 and D2.
Still just clean.
I have signal present right up to and including the base and emitter of Q4, with the exception of the base of Q2 where I would expect to see it but I don't. Scope probe impedance issue? Guitar signal downstream is everywhere, and is peaking around 100 mv AC.
Update: I've replaced q4 with an MPSA18 which is EBC. I now have a trickle of clean audio coming out the dirty side. Ive removed the blend pot, so I'm looking at the junction of the 1u cap and the 47k res. at the base and emitter of Q4, as I did before, I have a strong clean signal. Shouldn't be clean there. I'm putting almost 200mv AC tone in, and I measure 300 mv at the B and E of Q4. . Given the gains of the darlingtons, this signal should be crushing, right?
Still banging my head on the table. Now I have 3 MPSA18s and a 169 in Q2. Still very low output, which is a clean (not dist?!) looking sine wave of 300mvAc on the base and emitter if Q4, and drops to almost nothing at the collector. And i get no signal on the scope at the base of Q2, but it is everywhere else. The clean blend channel is fine.
Cap and diode orientation. Measured resistors in circuit. Triple checking and measuring trannys.
In past threads, I've found voltages listed for the problem units, but I haven't seen voltages for the 4 transistors posted for a working unit.
did you remove D1 and D2 by mistake? D3 and D4 are for removing.
The thing I hate about darlington's is that you cannot stick them in your meter's hfe-testing socket and turn 'em around until you get an hfe reading that makes sense.
Quote from: duck_arse on April 03, 2014, 11:06:18 AM
did you remove D1 and D2 by mistake? D3 and D4 are for removing.
Thanks! will try. But D3 and D4 are described at tonepad as being specified in the original schematic. Doesn't that mean they are the optional ones or the others, 1 and 2, aren't specified in the original, thus are optional. Having syntax issues here. However I do think I started off with all 4 out of curiosity. I have them socketed so I'll try. But, another spot where the language isn't clear, should any "omitted" diodes be replaced by jumpers? If it was 1&2, yes. 3&4 might be a bad idea for jumpers. So you must be right.
D2 and D3 are the diodes to remove from a scrambler. Perfect. Thank you sir.
Nice sound. Nice pedal. Next, Mr Hammer suggests getting something to clip before the scrambler, so I'll try that.
It's not so much that there needs to be a distortion before the Scrambler. Rather, my long-time flag-waving for inserting a modified Dist+ front-end ahead of a Scrambler circuit really revolves around a couple of useful elements:
- having some means to vary the compression/sustain of the input signal, to regulate the "lifespan" of the octave
- having some means to overload the Scrambler and achieve "implosion" sounds
- having some means to soften the input signal level and extract subtler octaving from the Scrambler
- having some means to vary the output volume level of the Scrambler
- having some means to tone-shape the input signal to get different Scrambler outcomes
All of that can probably be achieved in other ways, and certainly via the combination of other pedals with it. For example, a simple single JFET booster stage as the front end, with a variable treble-cut and level-attenuator just ahead of the Scrambler would accomplish a lot (though not all) of that. I found that a modified Dist+ front end did all of that reasonably well in a fairly compact and simple way; i.e., it did what *I* needed it to do. And because it was a simple thing to include, it meant one could hit a single stompswitch and the Scrambler would be "set up" to produce the desired sound resulting from the combination of two effects.
Ah, ok. I'll put a booster in front with a tone control. The octaves seem to come out more when the treble is rolled back, but lime another guy just posted, and unlike a lot of others I think, I prefer my pedals take responsibility for their own input level and tone, and not do it at the guitar. Sometimes I record split signals of one kind or another so I keep the guitar full up. And not every pedal can be first. Thanks
I think that'll work out well for you, Alan. Let us know how you like it, when it bears fruit.
Actually, now that I think of it, if you wanna throw a couple of switchable clipping diodes to ground on that output, in parallel with the treble cut, that might yield even greater flexibility.