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Topic: Audio-Probe Guide? (Read 6872 times)
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petemoore
Posts: 18836
As Yet Unrated
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A cap is used to block DC, a wire is used to connect to the amplifier input.
Shielded cable, 1 end gets shielding grounded at 1/4'' phono plug sleeve lug [cut a cable in half, lol..have 2 audio probes or...]
The tip connects to the signal wire in the center of the cable.
at the cut end of the cable, strip back the shielding say 1'', the signal wire to 1/2'', adjust as necessary to get it looking good, separate wires and all..
Twist the ends and put a DC blocking capacitor, solder a nonpolarized capacitor to the signal wire [rated higher voltage than the circuit input power will ever see].
Plug in the unadulterated 1/4'' phone end, attach the shielding to ground of the circuit to be probed, probe for AC/signal through the capacitor'd signal wire.
That's it, cut a cable, DC block the input, ground the shielding.
A little stretch of flexible ground wire, and insulating the ground [electrical tape] make it easier/safer to use.
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« Last Edit: October 17, 2009, 10:26:08 AM by petemoore »
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Convention creates following, following creates convention.
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Ripthorn
Posts: 1175
Brian T.
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Paul Marrossy (sp?) has a guide on his site diyguitarist.com for making a deluxe audio probe that is a little less rudimentary than the kind most of us use.
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Exact science is not an exact science
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peps1
Posts: 387
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Ok think iv got it.........?  And i take it I plug the guitar into the PCBs input and work my way though the circuit from input till i helpfully find a dead component etc? |
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aron
Administrator
Posts: 10305
Aron Nelson
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Yes, you listen to the sound of your circuit - working your way from the input to the output. BTW, it's easier to use a film cap like a .1uF or so. In any case, make sure your positive lead from the electrolytic is the one you are testing with.
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peps1
Posts: 387
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mmmmm.......not getting anything from the PCB at all.......just get a evil ungrounded sound till i put the probe on the tracer, then it just goes quiet with no input from the guita?
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aron
Administrator
Posts: 10305
Aron Nelson
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Try this first. Take your guitar and plug a cable into it. Now use the audio probe to listen to the guitar - touch the cap on the tip and the ground (black) clip on the sleeve of the guitar cable. Make sure that is working first.
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peps1
Posts: 387
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Try this first. Take your guitar and plug a cable into it. Now use the audio probe to listen to the guitar - touch the cap on the tip and the ground (black) clip on the sleeve of the guitar cable. Make sure that is working first.
Think i was being a little impatient.....seems to take a couple of seconds to start getting the signal, I followed it to the first transistor where i start getting a strange ping sound......so think my trouble my be only two components into the PCB (posted how i laid my trans out on the other thread if anyone wanted to take a little look) |
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sean k
Posts: 1184
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 This is mine... without a capacitor, and funnily enough the last time I used it I din't get DC but now that I think about it... the amp I was using had a cap on the input... thats why  Heres an idea. Once your guitar is plugged in, lie it flat on it's back, and get a piece of wire, 16 gauge, 1/16th, 1.6mm (all the same basically) or thereabouts at about 350-400mm long and thread it through the strings at right angles and set it where when you flick the wire it just keeps on bouncing for ages. Saves hitting the strings everytime you want some signal and also sounds alot better than the constant irritating drone of oscillators as signal generators. |
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