gear for trouble shooting

[nag hammadi]

i would like to expand my trouble shooting abilities a bit with some gear.

i have a good dmm.

i guess i need something in the way of signal tracer/ probe/ etc.

what are the differences between signal tracers, test oscillators, audio probes, etc?

suggestions on which to build?

also, my dmm is a nice fluke, but does not do capacitance.  does anyone know of a unit that ONLY does caps or maybe a cheaper dmm that also does caps?

thanks.

[Processaurus]

If you like electronics, picking up a used analog oscilloscope would be invaluable.  You can debug/design with a much more basic understanding of electronics with a scope.

[nag hammadi]

i will get a scope as soon as i can for sure.

i think my next step is to figure out the signal tracer (etc) stuff.

any help?

[petemoore]

signal tracers,
Have to check wikipedia
test oscillators,
Generates a tone so you have something easy/convenient as an input source, tape-ing down a key on an electronic keyboard also works as a source.
audio probes, etc?
 Wiki probably has diagrams, it is simply a connection to the input of an amplifier, ground & DC blocked [via series capacitor] signal carrier, usually a shielded cable is used [to reduce unwanted noise, with plug on one end, ground connector [w/alligator clip], and signal wire having a capacitor then a probe end [like on your DMM wire] so testing at various points in the circuit may tell at what point the signal is lost or otherwise not right for the circumstances of the circuit.
 Check out all the links, FAQ's, See 'Guitar Effects Oriented' [GEO], wiki some of the terminology.

[petemoore]

http://en.wikipedia.org/wiki/Signal_tracer

[nag hammadi]

what do you guys use?

[soulsonic]

When I'm tracing a circuit for a trouble spot, I usually just hook an audio generator up to it and start going through it with an oscilloscope.

[Paul Perry (Frostwave)]

I use an old secondhand audio generator, but there are plenty of (free) programs that will let you generate continuous tones from your computer soundcard.
Ideally, I suppose we would have TWO signal sources - one for doing guitar riffs (perhaps sample or rip a few riffs & put them on continuous loop) and a continuous tone for tracing the audio signal.
Which tracing you can do with the audio probe (see troubleshooting section) until you get that CRO.

[R.G.]

One thing that's worked well for me is to record a guitar note with high fidelity into a computer, then use one of the free audio programs to make a zillion copies of it and record that onto a CD track. Each track on the CD then becomes something like "Open low E", "Open A", "high E", "Twelfth Fret G" and so on.

You have to then go set the CD player's output to something like the real guitar's volume level and also worry about pickup impedance. You can fix these with a resistor divider and either a resistor or inductor-cap pickup faker. I've been doing this for years. The pickup faker at AMZ reproduces essentially the same circuit I picked up from the net a few years ago. I believe that the original article has now vanished from the net.

Find something, anything, to get 0.5H (wah inductor?) or 1-4H (transformer primary) in series with the signal. However, in most cases, if your pedal has a high input impedance, the pickup faking is not necessary at all.

Many people have sound cards and CD burners. Fewer have signal generators.

I have been intending to go down to my friend's vintage guitar store and record a CD of the same riff played on a bunch of vintage guitars with all the same setup and conditions to document what these ancient wonders sound like. Someday, maybe I'll actually have time to do that.... 

[nag hammadi]

how about a meter that does caps???

any suggestions?

[petemoore]

  how about a meter that does caps???
  I'd love to have one, use a circuit and 'comparative rememberances' to 'do' caps...tells me they're working and about what range...
any suggestions? Try to find one cheap [ya never know..].
  What I use for signal tracing should NOT be used on high voltage circuits...
  That said, connecting a conductive shaft to the output of my thumb makes a super quick and easy to find 'signal injector'..just look for sound like when you put your thumb over the end of a live cable feeding an amplifier...
  Starting at the output, say the live cable, then live cable in the output jack, then across the output cap, then working my way back to the input. a big dropout of volume is...where I lost the signal, and where debugging is needed. I use only this method for 95% of all 'problem' finding, 'solution' finding generally involves voltage and resistance readings.
  Just don't connect your thumb to a high voltage, use this method only on small voltages like: <30vdc. !
  A quick/dirty/effective signal injector.

[Ronsonic]

I've considered recording and marketing a trouble shooting CD and impedance matching kit for tinkerers and repair techs. The idea being you get a CD with samples from a variety of instruments both electric and mic'ed with a box that allows you to get a level and impedance match for the appropriate instrument. Synths would be basically straight through low Z gadgets while for guitar you'll have emulations of a guitar output and a mic'ed up amp. Those are easy and obvious. The fun and utility of the gadget would be the harmonica into green bullet mic at correct level and Z and Barcus Barry flute mic's and piano pickups and all the other goofy stuff most of us don't have handy.

Ron