EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: dexters_lab on March 03, 2014, 11:17:56 pm
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just something i picked up...
a well used 'Tester 301B' cable fault locator that uses TDR (http://en.wikipedia.org/wiki/Time-domain_reflectometry (http://en.wikipedia.org/wiki/Time-domain_reflectometry))
cant find much about these on the interwebs but it seems to date from about 1993.
Operation looks pretty simple, basic oscilloscope type view to see the waveform reflected with a moveable cursor on the trace using a 10 turn pot which simply changes a LCD readout to the distance from the device. It appears it measures from 100 meters to about 2 kilometers.
Came with an external psu for charging the internal ni-cd batteries (which are completely shot) so it's powered up with 12v from the bench psu.
Internally it's not as complex as i thought it was going to be.
I may do something more on my youtube channel if there is any interest?
Would welcome suggestions of things to try with it? It has no value to me so i can do anything to it >:D
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I would pop a new battery pack in it and use it. I know enough people who would like to be able to easily isolate a cable fault on a network and would use it.
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i could clean it up i guess
testing it might be an issue
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i could clean it up i guess
testing it might be an issue
Make yourself a cable simulator http://www.samhallas.co.uk/repository/documents/cable_simulator.pdf (http://www.samhallas.co.uk/repository/documents/cable_simulator.pdf)
They don't tend to trust the field technicians with test equipment that needs much skill nowadays. They are expected to use FastTest (voice response service into the line test system) and JDSU or EXFO hand held testers.
Jon
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perfect, i will try that out and see if it's working correctly
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Easier is you just take a full reel of cheap CAT5 cable and dig out the inside end, then simply join the 4 pairs in series. That way you have a 400m long cable, and can introduce opens or shorts at 5 points at defined lengths on it.
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hmm, i have a nearly full reel of STP Cat5 here i could try it with
would the STP shielding and it being in a coil affect the signal? :-//
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Not at all. Just use a pair and it will work fine. The beauty of twisted pair..... Being designed for phone cabling it will be a close match length wise on the meter reading.
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with thanks to those that have already commented i have done some tests with this using a part box of cat5
will be cleaning this up and will make some new battery packs for it (eventually)
BT Tester 301B - Time Domain Reflectometer (https://www.youtube.com/watch?v=gw_JAc7l8CA#ws)
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Wow haven't seen one off these in many a year. sorry for bumping an old post but I used to build these, the chances are I flow soldered this and possibly inspected it.
It should have initials on the underneath of the board GW if it was me or JF if it was June that inspected it.
edgcumbe instruments is now gone with a few blocks of flats replacing it thats progress for you.
Graham
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Sell it as a useful device for people with lots of long part reels of cable to sell, who need to know how much is on the part reel? Although I suppose >100m for a part reel would have to be a pretty big reel...
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Wow haven't seen one off these in many a year. sorry for bumping an old post but I used to build these, the chances are I flow soldered this and possibly inspected it.
It should have initials on the underneath of the board GW if it was me or JF if it was June that inspected it.
edgcumbe instruments is now gone with a few blocks of flats replacing it thats progress for you.
Graham
:-+
it's funny you used to make them, someone on youtube commented that they helped design the prototype!
i sold it at a radio rally last year
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I watched your youtube video earlier and tried to comment but they just disappeared |O
I do remember the front panel and case being designed at Edgcumbe Instruments when I was there.
The battery pack in one off these was blame for a fire that burnt down the new end of the factory back in the late 80's
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They don't tend to trust the field technicians with test equipment that needs much skill nowadays.
Given my experiences they are probably right not to trust them - mind you, it's their own fault for not training them properly. I had a 'technician' out to fix a fault on my voice line a couple of years back. He asked me what I could hear on the line -
me: "Just noise."
him: "What kind of noise?"
me: "Just white noise"
him: blank look
me: "You know, white noise."
him: blank look
me: "Gaussian noise?"
him: blank look
me: "Fsssssssshhhhhhhhh?"
Turns out that they are so poorly trained or educated nowadays that "white noise" is a phrase that not even sparks a vague memory of a training class half slept through. This despite "Signal to Noise Ratio" being one of their own official pass/fail criteria for a copper pair.
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I watched your youtube video earlier and tried to comment but they just disappeared |O
I do remember the front panel and case being designed at Edgcumbe Instruments when I was there.
The battery pack in one off these was blame for a fire that burnt down the new end of the factory back in the late 80's
If you have any information or documentation on this thing feel free to share it here. :-+ :popcorn:
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How about a picture of the production line post fire lol.
A slighty younger me holding a 301B