Sprout Tech Help

[jkokura]

I think if you search you should be able to find them. Really, all you need is a jack. Connect the sleeve lug to a wire and then connect that to ground of the PCB/jacks/switch. Then put a 100nF cap on the tip lug, and a wire from the other side of that cap. That wire is now your probe. Plug the probe into your amp and keep the volume low, and plug your guitar into the input of the pcb. Then you can probe around on the board. Lots of popping and noise, but if you listen you should be able to hear the signal at where the input wire goes into the board. Follow the circuit along with a schematic and layout and you should be able to find where the signal should go and where it shouldn't.

Jacob

[themachinerages]

Stereo or Mono jack? Does it matter?

I think I could definitely do this if I go buy a jack from Radioshack

[themachinerages]

Does anyone know if I need a stereo or mono jack?

[jkokura]

Either will work. Mono is probably easier.

Jacob

[themachinerages]

Thanks!

[themachinerages]

I built the probe and bought a multimeter. I have no idea how to use the meter and when I use the probe, I get no signal at any point on the board, even when I touch the probe to the input point.

I am getting really frustrated with this. Does anyone have some advice for me?

[mgwhit]

The best thing you can do with the DMM right now is check for continuity to ground from points in the circuit that should not have continuity to ground (i.e. shorts).  Set your DMM to Continuity Test setting.  Clip (or hold) your black lead to the ground plane of the board and then touch other portions of the board.  Confirm that parts that should be directly grounded are and that parts that should be, aren't.

As for the signal probe, if you're not getting signal at the input of the board, then your wiring may be wrong or you may have cold joints on the switch.  The only place I have ever had a cold joint (at least one that affected the signal) is on a 3PDT switch, so that's the first place I'd look.  Start testing for signal at the input jack and follow it through the switch.

If you can't get signal at the jack, your signal probe may not work.  Are you grounding it?  Good luck!

[themachinerages]

I have the probe grounded, yeah.

I am almost sure that I have the wiring correct and I resoldered for cold joints.

So I should have no continuity to the ground wire from any point? and if I do have a spot grounded, how do I fix that? You mentioned some parts should be grounded, how do I know which?

I apologize if these are amateur questions, I'm a complete beginner

[mgwhit]

To determine which parts of your board should and shouldn't have continuity to ground, you need to figure out which parts of the board correspond to certain parts of the schematic.  That may sound tough if you've never done it before, but it's a good exercise and a skill you'll need to pick up if you ever want to successfully debug a board.  Maybe someone with more time can mark up an image for you.

In the meantime, although you feel like your wiring and switch soldering is good, you can't detect signal at the board input with your new probe.  You really need to figure out what's going on here before you tackle the board.

Based on what you've said, there are several possibilities:

• incorrect wiring
• cold solder joints on the jack or switch
• bad hardware (jack or switch)
• non-functional signal probe
• incorrect use of signal probe
• guitar plugged into wrong jack (don't laugh, we've all done it)

I think the first thing you should do is confirm that your signal probe functions correctly.  With your probe plugged into your amp and the guitar plugged into your input jack, connect the probe ground to the sleeve (ground) lug of the input jack.  Strum the guitar and touch the signal probe tip to the tip lug of the input jack.  Heck, touch it to the tip of the cable plug itself.  If you get sound, the probe works; if you don't it doesn't.

If it works, start tracing the signal from the jack towards the board.  Do you have signal on the input lug of the 3PDT switch?  If not, you've got a cold joint or a broken wire on that connection.  Moving on, do you have signal on the output log of the switch (the one that connects to the input of the board).  If not, you've got a cold joint or a broken wire or a bad switch.

Good luck, and let us know how it goes.

[themachinerages]

Thanks for the responses mgwhit!

I tried your test to see if the probe is working and it appears that it isn't

I followed Jacob's specs so I'm not sure what I did wrong

[jkokura]

Perhaps a picture of what you're working with might help us see what's going on for you?

Jacob