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 Post subject: Signal tracer build
PostPosted: Aug Tue 03, 2021 6:08 pm 
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Location: New Hampshire
Think this design might work?
- http://www.zpag.net/Electroniques/Engli ... tracer.htm

I have everything but the transistor which looks cheap enough on eBay, I was wondering as it looks very simple compared to some others designs I looked at.

I would be making it to troubleshoot Transistor radios, If anyone had a link to simple low parts one I would appreciate it.


Henry


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 Post subject: Re: Signal tracer build
PostPosted: Aug Tue 03, 2021 7:25 pm 
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Joined: Jan Fri 27, 2017 8:41 pm
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Location: Springwater, NY
Here is a link to a bare PCB, both AF and RF ( Antique Wireless Association Signal Tracer )

https://www.antiquewireless.org/homepage/pcb-item-3/

and here is a link to one already built:

https://www.ebay.com/itm/203532039348?hash=item2f637474b4:g:8gkAAOSwPnFg-EeD


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 Post subject: Re: Signal tracer build
PostPosted: Aug Tue 03, 2021 8:41 pm 
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Joined: May Tue 30, 2006 4:46 pm
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Location: Santa Rosa, CA
The simple one-transistor circuit will work, but may not be very sensitive. Most any small NPN transistor should work.

I built one using 2 ICs, an op-amp and the usual LM386 audio amp. I think the AWA version uses just the LM386. The AWA board appears to have an RF-input option, so you can use it to check IF stages in radios by detecting the signal with a diode.

My tracer was similar to this:

Image

Rich


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 Post subject: Re: Signal tracer build
PostPosted: Aug Tue 03, 2021 8:53 pm 
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Joined: Jun Sun 15, 2014 5:37 pm
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Location: Montreal, Quebec
I'd definitely go with something a bit fancier, for proper gain. Better to have too much than wondering if you have no signal, or the tracer isn't sensitive enough.


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 Post subject: Re: Signal tracer build
PostPosted: Aug Tue 03, 2021 9:35 pm 
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Location: SoCal, 91387
Henry, if you were to add a Diode in front of the cap, it could be used to trace RF as well, although as others have said, the gain -with only one Transistor to amplify, may not be sufficient.

You can use any portable Transistor radio as an amplifier. Simply connect one probe lead to the center lug of the VC, and the other to ground.

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 Post subject: Re: Signal tracer build
PostPosted: Aug Tue 03, 2021 10:17 pm 
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Location: New Hampshire
I appreciate the help! This may be one of those projects where I have to experiment a bit, as amp chips nor NPNs are hard to come by.


fifties wrote:

You can use any portable Transistor radio as an amplifier. Simply connect one probe lead to the center lug of the VC, and the other to ground.



So I can use a transistor radio as a Signal Tracer? Do you perhaps have a schematic?


Henry


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 Post subject: Re: Signal tracer build
PostPosted: Aug Tue 03, 2021 10:23 pm 
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Location: Wayside, NJ Monmouth
You could use this as the basic amp, then add a diode probe. Has up to 1 watt output. Gain adjustable form 0, 20 40 db. And uses a FET op-amp input. A P.C.B is still available from FAR Circuits.


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 Post subject: Re: Signal tracer build
PostPosted: Aug Wed 04, 2021 1:01 am 
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whfh99 wrote:
I appreciate the help! This may be one of those projects where I have to experiment a bit, as amp chips nor NPNs are hard to come by.


fifties wrote:

You can use any portable Transistor radio as an amplifier. Simply connect one probe lead to the center lug of the VC, and the other to ground.



So I can use a transistor radio as a Signal Tracer? Do you perhaps have a schematic?


Henry

No print needed. All a signal tracer is, is an amplifier. Any radio can be used as an amplifier, either tube or Transistor. Simply connect one probe lead to the center lug of the volume control, and the other to the radio's ground. I would recommend however using a Transistor radio for this when tracing another, so there's no worries of high voltage damaging the set under test, as there might be with a tube set.

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 Post subject: Re: Signal tracer build
PostPosted: Aug Fri 06, 2021 2:42 pm 
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Like this?

Of course, the radio being used as the Amp would be turned on with a speaker attached. But just wanted to make sure it was connected right.

Also thanks for the schematic N2LXM.


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 Post subject: Re: Signal tracer build
PostPosted: Aug Sat 07, 2021 5:24 am 
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That looks correct, but to make sure, test it on a working radio first.

_________________
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 Post subject: Re: Signal tracer build
PostPosted: Aug Sun 08, 2021 2:11 am 
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Great,
I got an alligator clip and MM probe set up with a cheap tinny sounding transistor set.

Can someone explain or post a link to a YouTube video on how to use a signal tracer like this one?

Henry


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 Post subject: Re: Signal tracer build
PostPosted: Aug Sun 08, 2021 4:42 pm 
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Location: New Hampshire
here's a pic, the speaker "grill'' is to protect the cone. My test subject was a cobra "two" radio.


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