If you would like to build a cable tester for your 4-wire, 6-wire (or 8-wire) modular connector cable
then here is a schematic and some (minimal) instructions.

What you will need in skill

What you will need in tools

BOM (Bill Of Materials)

Schematic

Minimal Instructions

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What you'll need in terms of skill:

This project is VERY simple, but you will need to be able to handle a hot soldering iron without burning your self, anyone or anything else. You need to be able to make clean hot solder joints.


There are no static sensitive parts, so you will NOT need to worry about ESD protection.

You will need to be able to identify electronic parts. Especially resistors by color code and the Anode and Cathode side of LED (light emitting diodes).


You need to be capable of building this project without considering litigation if you screw up and hurt yourself because you did NOT wear appropriate eye-protection, you breathed solder fumes or you started this project thinking you had more capability than you actually had.


You need to be over 18 years of age! You need to be born on another planet and you have to have been impregnated by some ancient life form which just happened to be passing by, and which cannot be CARBON based in nature. You must also not be a carbon based life form!


If you meet all the above requirements, then proceede!

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What You Will Need In Terms Of Tools:

  • You will need a soldering iron.
  • Phillips screwdriver #1
  • Needle Nose Pliers (or Radio Pliers if you have them)
  • Electronic Solder
  • Patience
  • Diagonal Cutters (or Wire Strippers)
  • Protective Eye wear
  • A good and clean working surface
  • Several non-alcoholic drinks of your choice
  • Hookup wire (multi-stranded AWG #20 or #18 should be fine)
  • All the items listed on the BOM.

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BOM

Schematic*

RS Part Number

Quantity**

Price***

Description

PCB

276-150

1

$1.19

Project Solder Board

Battery Connector

270-325

1

$1.39

9V Battery Connector

Battery Holder

270-326

1

$0.99

9V Battery Holder

SW1

275-1571

1

$2.39

NO SPST Switch

D1..D10

276-081

1

$2.99

LED Bar Graph

R1..R8, R10

271-1311

2

$0.49

100 Ohm ¼W 5%

J1, J2

279-420

2

$4.99

RJ25C Jacks

Enclosure

RSU11521226

1

$2.19

Enclosure

* --- Part as listed on the schematic (some parts may not be listed on the schematic, such as the PCB, but have a BOM listing.

** --- Quantity needed to complete the project. Some packaged parts may leave you with extra parts.

*** --- MSRP

The parts listed are Radio Shack part numbers from the 1998 Radio Shack Catalog. You may have spare parts which work just as well. Additionally the schematic and BOM show a 9VDC battery being used. To make the thing smaller and to fit into a nice enclosure box which I had around, I used two lithium battery holders connected in series to give me 6VDC. Works fine that way too. Additionally, I am not supporting Radio Shack as the parts vendor, I included the Radio Shack numbers because Radio Shack is virtually omni-present. I built 2 of these for the price shown above buying new parts from other vendors besides Radio Shack.

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Minimal Instructions

The schematic shows how to complete one circuit for one LED segment of the bar graph.

To do the others, you simply have to connect the other 5 wires (for a 4 or 6 wire tester) or 12 wires if you are doing both a 6-wire and/or 8-wire tester.

If you are using the RJ25C (6 wire connectors and jacks) you need to hook up R1 through R6. If you want you can also hook up R7 and R8 and double the wires on R1 throught R6 for both an 8Wire tester and a 6 wire tester. The 8 wire tester is for testing the DEC cable.

The switch which is hooked via R10 is to be used as a Battery test switch. Press the switch and the 10th LED will light if the battery is good.

The "BUS" indications are places where all the wires at that point can be connected together. I completed the bus on J2 by simply hooking the internal wires to the same lug and then using one wire from this lug out of the housing to the battery.

I didn't bother to put mine in an enclosure at first. But the wires kept getting caught on things. So I popped it into a small box. If you put this thing into an enclosure, be sure to insulate it from the case, or use a plastic case.

The BOM shows a cost of about $22.10(US), but I built mine for under $20.00(US).

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