Audio probe signal tracer .

[anderslober]

I need to build one of these cheapo tracers. I have seen Billm's diy video on youtube.......BUT, he omits some very important information.

What direction is the 0.1uf/400v capacitor mounted? To which end does the '-' go??

He uses a capacitor, nail, Radioshack mono speaker and some cable/wiring.

Any info would be good. Thanks.

 

[nashvillebill]

I have no idea what video you are talking about.

The concept of a signal tracer is pretty simple though. You take some sort of small amplifier, anything that has a speaker and can amplify a signal. You make an input cable, like any input it's going to have a signal wire and a ground wire. The ground wire of the input cable gets an alligator clip and clamps to the chassis of the Device Under Test. The signal part of the input wire gets the capacitor. You can put the cap anywhere in the signal wire. The cap is there to block any DC that might be present wherever you touch your "probe".

Here's the manual to the signal tracer I have. It's explanation of its use may help you understand it: http://www.stevenjohnson.com/manuals/mfiles/philco-7030manual.pdf

 

[anderslober]

Here is the video: http://m.youtube.com/watch?v=IEcyDzYAsuU

I need to know which way the cap is mounted. The '-' towards the probe tip........OR......?

 

[cademan]

It's not an electrolytic so it doesn't matter. Some say the mark on one end is the outer foil connection and that it makes a difference in the sound quality or something but frankly I have never noticed that it made any difference which way it was mounted.

 

[anderslober]

Ok......is it a non-polar cap? The fellow in the video does not state what kind of cap it is.
0.1uf/400v BP cap?

 

[jeromach]

It's a point zero one capacitor, i.e. 0,01.

This information directly indicates we're not talking about electrolytics here, therefore there is no polarity.

But a little investigating (following the link that is in the video) gives that he used a "Mallory 150" capacitor, looking something like this;

 

[anderslober]

ok...cool...thanks.

 

[jeromach]

Good luck, I'll be making one too I think, saves me getting my scope from storage all the time.

Greetings from Holland, it was nice to be in Singapore a couple of times

 

[GD70]

That's great! Really simple. I think this will help me with my current amplifier I trying to fix.
Thanks for the you tube link.

Cheers,Glenn

 

[Watthour]

Anders - If you insert a detector diode and small ceramic cap in series with the input (selectively) you can also trace RF signals.

These are handy, and they pop up occasionally on ebaY and CL:

 

[ferninando]

I too have the RS tracer and the schem.
I could scan it and email to you.
PM me

 

[transmaster]

Built something similar but I used a gutted BIC pen for the probe. Works great.

 

[elnaldo]

I built my probe with a 1uF polyester cap. No problem with that. The cap should be large enough to allow low freqs to pass. The voltage rating should be large enough to block the DC present in the circuit under test, so 400 V is a very safe value. If you are going to measure tube amps with higher voltages, go up to 600V or more.

 

[Baron K Rool]

Just take some cheap computer speakers from a flea market. Cut off the 3,5" plug and connect the GND to your amp's chassis, and one of the input wires to wherever you want to trace your signal. If there is one, it'll play through the speaker. Otherwise, it won't.

These are usually quite rugged and won't die even if exposed to lots of DC.

 

[transmaster]

In my case I have a 1958 Military Audio Oscillator TS-382F/U that weight in at about 40 pounds moving it is not a option I had to come up with something and the BIC pen thing I came up with.

 

[Binkman]

I made one and the problem I'm having is if you hit a sour spot you get this audibly brrrrrrrrrrrrrrr... LOL.... like hit the wrong leg?

Can rig something up so 'if' I get audio I hear it but hit a sore spot the circuit eliminates the audio? Like a small relay kicks in and cuts off the audio but shows a light that tells me it's "hot" or something?

thanks

 

[elnaldo]

A capacitor should block anything and just get audio signal. If you get any noise, it should be audio signal.

 

[anderslober]

I ordered the Ratshack amp...........will post when I have completed the construct!

 

[Rolf Zetterberg]

A transistor tracer almost always has a low input impedance.Somewhere I read 5kohm!It will load some valve circuits hopelessly.
A FET-follower or a high impedance transistor stage is a simple fix.

 

[Peter Newman]

I also want to make one of these referenced in the OP's video, but I am having trouble locating the same style and value of resistor used. Would this one be suitable please

10nF
400v DC
Metallised Polyester