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Old 31st Aug 2016, 9:36 pm   #1
tim.norris
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Default Velleman K7000 Sig Tracer/ Inj Kit

Have purchased the above kit , is it possible to purchase ready assembled screened probes or is it a diy project ?
regards, Tim.
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Old 31st Aug 2016, 9:52 pm   #2
martiR2R
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Default Re: Velleman K7000 Sig Tracer/ Inj Kit

Would scope probes work?
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Old 1st Sep 2016, 2:41 pm   #3
pbengtech
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Default Re: Velleman K7000 Sig Tracer/ Inj Kit

My local technical college used old BIC biros with the insides removed and copper wire glued inside as probes. They were short of money in the 1970s.
Very cost effective and stronger than probes....low voltage only of course.
😀 Phil.
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Old 1st Sep 2016, 4:42 pm   #4
David G4EBT
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Default Re: Velleman K7000 Sig Tracer/ Inj Kit

I've made quite a lot of K700s, often as gifts for friends. Great little kits, and by far the easiest way to track down faults in all stages in both valved and solid state radios. I always make my own probes - an AF probe which can be used for both injecting a signal, or signal tracing, consists simply of a high voltage 0.1uF cap to protect the K7000 should you inadvertently put the probe on a high voltage point in the radio under investigation. (There are isolation caps on both the input to the tracer and the output of the injector (C4 & C5) on the K7000 PCB, so another one in the probe isn't strictly necessary and is just 'belt & braces' on my part).

An RF probe for RF signal tracing can have a germanium diode included. There are many designs of such probes - I've attached a couple of circuits and a couple of pics of probes that I recently made. The AF one is in a felt tip pen tube - the RF one in a felt-tip maker case, of larger diameter. To house the kit, I usually knock up a little comb-jointed wooden box, along with a small speaker and a couple of phono sockets on the front panel for the injector and tracer facilities, and I add a high brightness/low consumption LED. I use scrap PCB for the front panel, sprayed white.

Great fault-finding aid. In a dead set, you can inject a signal at the slider of the volume control, and if you hear nothing from the speaker, there's a fault to investigate in the audio stage. Then applying the probe in the tracer to the slider of the volume control, if you hear tunable signals, you know that the RF/IF stages are working fine. If not, you can work your way to the front of the set till you hear signals.

Obviously there are other preliminary tests to carry out - voltage and continuity tests etc, and I don't want to infer that signal tracing/injecting is the only approach, but going right back to schooldays back in the 1950s, it's the method I've relied on most and had most success in speedily pinpointing faults.

Hope that helps a bit Tim.

Have fun!
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Old 1st Sep 2016, 6:06 pm   #5
tim.norris
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Default Re: Velleman K7000 Sig Tracer/ Inj Kit

Thanks for the prompt replies , David it`s a wow from me that box is a work of art , will do my best and have a go ,but me thinks its never going to be as good as yours , thanks again, Tim
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Old 1st Sep 2016, 6:40 pm   #6
60 oldjohn
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Default Re: Velleman K7000 Sig Tracer/ Inj Kit

In reply to David, I wish I had put HV caps in my K7000, guess why?

John.
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