Building my test rig - probe, oscillator

[tjdracz]

Hi there!
After using my less than efficient method of debugging circuits, I've decided to build myself a test rig with signal oscillator to do some signal debugging by probing.

Now, I'd like to use this as an oscillator: http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=2316&g2_serialNumber=2 - based on RG's project. Seems to be everything I need.
Now I've got couple of questions of how to wire this damn thing up!
I guess I need DC input there, output jack to send signal to amplifier and probe.
Now, bear with me. From dc jack I wire ground to the jack sleeve and +9V to the vero for oscillator. Also connected to DC jack, two alligator clips for debugging. Red one for +9V and black one for ground. Then yellow alligator clip for input to the tested board connected to generator vero output. Finally the testing probe connected to tip and sleeve of output jack on one end and with alligator clip and capacitor/probe at the other.
Does all of that wiring make sense?
Below is the picture of the wiring (sorry for the quality)

Now, do I need 9V/GND from DC and also GND for probe or will only one do? Also, what happens if I were to debug a -9V board? Do I need a voltage inverter there to make it work with +9V oscillator? And what happens with probe GND connection?

Thanks!
Tom

[duck_arse]

geeze, if only you'd written the colours yr using on those nasty looking clips on yr diagram, I'd be able to follow the whole thing.

you need a supply for the test osc, V+ and ground. the circuit under test needs a supply, and a ground common with the signal source, yr osc. the recieving amp needs a supply voltage, and a ground common with its signal source, which is your circuit under test. the amp doesn't supply yr test osc, likewise you don't need to power the c.u.t. from the osc supply. ground is the -ahem- common thread.

so, it follows, if you have a dc blocking cap at the osc output, and another as the probe input, and the c.u.t. has a ground common with both, it doesn't matter what polarity any of the devices is powered with/by. but I've been wrong before.

[tjdracz]

Sorry, I should have put the colours there but though picture was self-explanatory (not!)

Okay, so let me make sure I understand everything and the explanation is idiotproof (meproof):

- Connect all the grounds together say to output jack sleeve
- Add two blocking caps, one at the vero output, one as the probe in (so two caps at the probe? as it already has .1uF or so at the tip)
- If I'm powering board with 9V using alligator clips is it as easy as just swapping the clips around to provide power to positive ground circuit?

Sorry for stupid questions, just wary of the "Don't mix positive and negative ground circuits" credo everywhere and don't want to fry anything.

[duck_arse]

ahhh, now, you see the value of "a circuit diagram".

I can't read the osc vero, my eyes hurt and it's late. it's up to you to find if there is a cap at the output or not. as for the audio probe, it is really only a cap and a bit of wire, the cap is there to block dc, it is a blocking cap. you won't need a second one there.

all the grounds together, yes. the jack sleeve is as good a place, they don't really need to all be the same point tho (in this case).

keep reading the "don't mix", and be afraid. remember the ground is commoned between all? that leaves the positive to supply yr osc. now if you connect (ahh, the circuit diagram ...) the pos grounded circuit's supply to the ..... where? ground? positive? that's why you use a voltage inverter for pos ground effects when you want to daisy chain, because that's what yr trying to do here, chain the neg gnd osc w/ pos gnd c.u.t.

am I confusing you enough yet?

[tjdracz]

Nah, think I got all I need now! Ta

For the sake of completeness: oscillator schematic from R.G: http://www.geofex.com/FX_images/q&dosc.pdf

[GibsonGM]

Put the oscillator and the audio probe w/amp & speaker in the same box. You can run it off a 9V battery or add power supply banana jacks or what have you.

You add 3 banana jacks on the front:
Osc. out to circuit input (or wherever)
Audio probe
Ground which clips to circuit under test (CUT)

Done.   Make jumpers with the banana plug on one end, alligator clips on the other. I use an old red meter probe on my audio probe, so I can move it around easily.

Your ground on the panel is of course connected to the grounds of the oscillator and probe amp inside the box, so all the grounds connect together. 

[duck_arse]

I was thinking about this, laying in bed last. if you get a 9V battery clip, and connect the red wire to your grounds, and an alli clip to the black wire, when you need to power a pos ground circuit, you just clip the black to c.u.t. supply, add the battery, and you have -9V. disconnect the battery, it's all back to normal.

now, back to sleep ...... where did I leave those sheep ? .....

[cab42]

A few weeks ago I rebuilt my test rig to something like this. Before it was a true bypass box with in and out Jacks and Four alligator clips (Efx in and out, 9v and ground) and the oscillator in a separate box that I plugged into the input Jack, but I got fed up with plugging/ unplugging it when using my guitar as input. Also it was very noisy as it was plastic boxes. Now I have the oscillator built into the (new metal box) and connected to the tip of the input Jack and a switch so I can choose input.

I Can reccommend adding a level pot on the output of the oscillator as described in the pdf. It is incredibly loud.

I like the idea of using bananaplugs for changing between alligator clip and prope. I just use the alligator clip.

I have never built a positive Ground circuit so i haven't thougt about that at all.