Help debugging Ampeg Scrambler. Fixed, thanks everyone!

[nelson]

I cant seem to get my Ampeg Scrambler Clone to work. :cry:
I get no sound when effect is engaged, bypass works fine.
It is the Scrambler from www.tonepad.com
I have double and triple checked for any "solder bridges" fixed one, didnt sort it.
I have checked the pinout of all the transistors and orientation of electrolytics.

I didnt put in the diodes that "werent in actual units".
I used 1N914 silicon diodes instead of 1N456.

I have used home made darlingtons Using 2n5089'S for Q1, Q3 and Q4, Q2 is 2N3904. No other subs.

Battery 9.01v

Here are Q voltages


Q1

E 3.19V
B 2.86V
C 8.61V

Q2

E 0.23V
B 0.86V
C 3.74V

Q3

E 3.21V
B 3.87V
C 8.61V

Q4

E 3.21V
B 3.86V
C 8.61V




Thank you  
Paul Nelson  :cry:

[nelson]

Does no one want to help me?  :cry:

[smashinator]

Does any "clean" signal get through when you turn the blend knob?

It might be worth your while to inject the signal and see when it stops going through (I'd start at the out put jack and work backwards).

[nelson]

Nope, no clean signal getting through.


I guess i should build an audio probe....never needed to before.

I have some annoying input jacks that are for putting on the end of cable, website didnt show a picture or decent description when i bought them, I can finally get a use for them.  

In doing the "finger" test earlier the signal seemed to stop at Q3.

Do the voltages look OK? I should really learn more theory.  :oops:


Thanks for replying smashinator.

[KORGULL]

I'd say your Q1 looks a little off - base should have a bit more voltage on it.
The base shouldn't be lower than the emitter.
I had one of these (working) on the breadboard last week, here's my Q1 Voltages:
E=3.39V
B=4.29V
C=9.04V

[Connoisseur of Distortion]

i'm with korgull on this one. my guess, check the values on R1 and R2, and also see if there is a poor connection on R2 somewhere. tell us how it goes!

[nelson]

Spot on, I put 2M resistors in R1 and R2 positions instead of 1M, it seems that the person who marked the value of the resistors before shipping made a mistake, I should measure or read the resistor colour codes in future. I will replace them and update.

I was ready to launch it at a wall.

Thanks Korgull and Connoisuer.

:lol:    

[nelson]

Ok, I have replaced the resistors, it still isnt working, I have just realised I have wired the DPDT footswitch wrong wiring the input jack to the output lug and output jack to input lug.  :x  :x  :x  :x  :x  :x  :x  :x  :roll:

I am hoping this is it, but after messing around with it so much, the wires have started to break from the connections on the PCB.  :x  :x  :roll:

well here is hoping.  

[nelson]

Right, I am getting sound out now, however it doesnt sound right, its pretty much clean no matter where the pots are, with horrible clipping occasionaly but that could just be it clipping my soundcard (its late here, cant stick it through any amps might envoke the wrath of my g/f).


here are Q1's new voltages after replacing the 2M resistors with 1M, pretty much identical.

Q1

E 3.14V
B 2.83V
C 8.61V

I am going to build a new darlington just incase thats the problem.

Any other suggestions?

This is really P*ssing me off!  :x

Thanks

[niftydog]

you wrote that the battery voltage was 9.01V, but that must have been out of circuit, because all the other readings show it to be 8.61V. Whether that is significant I can't say, but you could do with a fresher battery all the same just to be sure.

checked the value of R3?

Given your unfortunate encounter with badly labeled resistors, I'd be checking through them all, again, can't be too sure!

I am going to build a new darlington just incase thats the problem.

that statement rings alarm bells. What do you mean "build"? Ah... I see, homemade darlingtons... that's a potential source of d'oh moments! Triple check those puppys, and maybe swap Q1 for Q2 or something.

The 5306 darlington listed in the project has a Vbe max of 1.5V. This means that (provided the circuit is working properly) the transistors should have a fairly constant 1 - 1.5V difference between base and emitter. All of yours show around 0.6V, which makes me think there's something up with your homemade darlingtons. Even the voltages given by KORGULL show 0.9V.

[nelson]

oops 220M resistor for R7 instead of 200 ohms. Thats my fault!  :oops:

I will change that before I start with the Trannies, I didnt use sockets,  :x  :x

This has to be my most problematic project yet. It has been sitting there mocking me for weeks after I initially assembled it and it didnt work.

Thanks for the tips nifty.

[nelson]

Ok, after replacing 200M resistor with 200R I am now getting these voltages on the trannies



Battery 8.94v In circuit.




Q1

E 8.29V
B 5.79V
C 8.94V

Q2

E 8.32V
B 6.12V
C 8.94V

Q3

E 8.30V
B 7.77V
C 8.94V

Q4

E 8.29V
B 7.77V
C 8.94V


After all this it looks as if Q4 is also orientated incorrectly :oops:

base is going to emitter an vice versa.

AAAAAAAHHHHH!!!! :x  :x  :x  :x  :x  :x  :x  :x  :x  :x  :x  :roll:  :roll:  :roll:

[niftydog]

yikes!

Ok, keep in mind what I said about the base-emitter voltages. Nothing is going to work until the base is approx 1V higher than the emitter on all trannys.

Word of advice, clip the black lead of your multimeter to a ground point and measure using only the red lead. Saves stupid errors.

[nelson]

Ok, I am getting some sick arsed fuzz now.
I wont know till I can blast my amp if it is working exactly like it should.
I changed the orientation of Q4 and it seems to be working.
I will post voltages and sound samples for future reference as soon as I know it sounds like it should.

Plus I have to mend the wires going to PCB they are making the effect intermittent.

Thanks for your help.

[nelson]

I spent a few hours playing with the scrambler clone today, it sounds EXACTLY like the samples at tone frenzy.
I cant imagine I will get much use out of it, although  it may be good for that special lead part. You can get a good stoner rhythm sound if you lower the guitar volume and have the blend quite low. I reckon if I use it with some amp overdrive it will sound nice for rhythm, nice "ghosting" with held chords, particularly good for "sludgecore" "doom".

When everythiing is running up full it sounds like sonic chaos, ring mod tones, octave up/ring mod tones on the high notes. Chords are completely deconstructed and sound like absolute noise. I think I will get some use out of it, but it could cause fatigue pretty fast.

I have it in a plastic enclosure and to my surprise the effect is not noisy and only picks up radio signal when I touch the shafts of the pots. I wont be spending the money on an enclosure for this one, unless it suddenly becomes key for a particular song. Certainly a fun pedal to have and I would recommend it to anyone.

I wont bother posting voltages.

Again thanks for your help everyone, your suggestions were invaluable.
This forum has to be one of the best on the net.  


Nelson

[Fret Wire]

Congrats..pretty wild eh?  Did you use a film cap for C3 (1uf)? Tonepad has the electro polarity backwards on that one, the pos lead should go the Q1's emitter. Not a problem if you use a film cap, but with an electro, it can pop and other wierdness if backwards.

[nelson]

I didnt notice any pops, it functioned 100% as it should. Do you mean C2? if so the positive side is going to Q1 emitter on the layout. C3 isnt but I dont notice any problems. no popping when switching no noise etc. Maybe francisco updated it.

[Fret Wire]

No, it's C3, a 1uf. The pos side is supposed to go toward the emitter of Q1. I used Panasonic film 1uf's, so I never had to worry. GGG's schematic has that cap the right way. But...if it's working fine, don't worry about it.

Looking at Tonepad's schematic and layout, they still show the neg side of C3 going to Q1's emitter.

[nelson]

I just checked whether or not I switched C3 round, I remember reading it in other posts when browsing. I didnt, I think I will swap it round, see what happens. I did notice a pop when I was recording the pedal directly to comp, but not when it connected to my amp.

Thanks for reminding me of that fretwire.  

[smashinator]

I'm glad to hear you finally got it working.

Just a quick note about using the scrambler.  I found that it sounded best (going into my cheap SS amp) when I ran it into the amps distortion channel.  I could get some awesome pseudo-feedback sounds with the texture set to the extreme end.  By itself, I didn't find it particularily useful.

All the same, it was awfully hard giving it to my brother (I built it for him).  I guess I'm going to have to build myself another one.