Huge hum, tiny signal, controls do nothing; Ron Black Tube

[dc197]

Hello everyone
I am new here.  I was wondering if you have any suggestions for debugging a project.  
I have assembled Ron Black's tube distortion in the bread board and upon testing it all I could hear was hum.

Schematic:


Circuit:
https://schematicheavencom.secure.powweb.com/veffects/tubedist.pdf


A complication is that the tube needs an AC-DC supply, so the circuit has main power to it, creating hum.

I have tested the PSU and it is OK.  It generates +11.7 and +5.8 V.


The symptoms:
* I can hear the guitar but very faintly.  It's overpowered by mains hum.  * The controls on the circuit (pre-cut ["gain" even though it's not actually a gain] and post-cut) do nothing, even with both turned all up and all down the sound it the same.

Some questions:

1 Do I need to use screened cable throughout?  Even for connections between different parts of the circuit?

2 Do I need to screen the bias to the tube, or just the signal?  

3 To debug, should I try this: remove the tube, use battery power, bypass the tube section.  This will check that the IC is working OK.
(In the diagram, connect pin 12 to pin 6 of the IC)?

4 How the hell do I get rid of all that hum!?

Any more suggestions?


Many thanks in advance

Daniel

[george]

check everything that should be connected to ground is

[KMS]

I think george is on the right track.  be sure the ground of the guitar signal is connected to the ground of the circuit.

[KMS]

A complication is that the tube needs an AC-DC supply, so the circuit has main power to it, creating hum.

The DC supply is filtered, so the hum should be minimal unless you have a shorted  filter cap, you know the big caps on the supply portion of the circuit.  

I still think that if your sure there are no cold solder joints, that you need to check the wiring and be sure the (-) guitar signal is connected to the ground on the audio portion of the circuit. That should fix it.

[toneman]

if U R measuring 12V(approx) and 6V(approx), U don't have shorted pwr caps.
As George said, ohm out all returns(gnds) to each stage of the circuit.
first Opamp is for gain.  Last OA is buffer.
Very similar 2 a PAIA SIAB(Stack-in-a-Box).
Got pwr & gnd on the *correct* pins of the OA??
The 747 is an ancient OA.
At least the 747 i'm familiar with is a quad 741.
Check the data sheet *4 sure* 4 the pinouts!!
Usually, on an 8pin dual OA, + is pin8 and -/gnd is pin4.
LetUsKnow what OA U R using.
i ohm i ohm, it's off 2 ohm i go......
Resistance is *not* futile!! It's absolutely Necessary!
(at least, in the right places...)
stayohmed
tone
back 2 meditating....ohmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm

[dc197]

Thanks for the tips guys.

I will check the GND of the axe, I actually think it was not connected to GND of the circuit (doh!).

What I meant by the AC supply creating hum was not via the DC supply (hopfully the ripple is minimal) but by there being a 240V cable passing right by my breadboard (wall outlet into the transformer).

I am not using a 747 but an 072, and yes I have pin 8 at +12V and pin 4 at 0V.



Should I try isolating the tube part from the OA and just testing the gain and buffer stages?

Many thanks

Daniel