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Q: Loopback Tester ( Answered 5 out of 5 stars,   1 Comment )
Question  
Subject: Loopback Tester
Category: Computers
Asked by: nelson1805-ga
List Price: $2.00
Posted: 05 Nov 2002 05:22 PST
Expires: 05 Dec 2002 05:22 PST
Question ID: 99207
How do i Make up a loopback tester fot a Parallel printer port 25 pin

Request for Question Clarification by jackburton-ga on 05 Nov 2002 05:42 PST
Parallel Port Loopback (IBM, Checkit and Most Others)
- Used to verify that a Printer port is working.
--------------------------------
Name		Pin	Pin	Name
Strobe	1	13	Select
Data Bit 0	2	15	Error
Acknowledge	10	16	Input Prime
Busy		11	17	Select In
Paper Out	12	14	Auto Feed XT
--------------------------------
Is this the information you're after??

Clarification of Question by nelson1805-ga on 05 Nov 2002 05:59 PST
I need to test a parellel port (printer port or cenertronics)
so need to make up a loop back tester to use with checkit, so need the
wiring diagram to make one up my self
Answer  
Subject: Re: Loopback Tester
Answered By: koz-ga on 05 Nov 2002 10:33 PST
Rated:5 out of 5 stars
 
Hello!

've found a page that describes the Parallel Port lookback cable
diagram to be used with CheckIt:

http://www.hardwarebook.net/cable/loopback/parallelportloopbackcheckit.html

This table seems to agree with the one jackburton-ga posted, the pins
are connected as follows:

Data Bit 0 (pin 2) -> Error (pin 15)
Select (pin 13) -> Strobe (pin 1)
Paper end (pin 12) -> Auto Feed (pin 14)
Acknowledge (pin 10) -> Initialize (pin 16)
Busy (pin 11) -> Select Input (pin 17)

So that's the easy part, the hard part is building the connector. 
There are a couple of approaches, the simplest I've found is to take a
raw 25-pin connector a solder the necessary pins together.  You could
also get an empty connector and insert the appropriate crimped pins
into it, but that requires a special crimping tool which is costly.

You will need the following parts
1) A 25-pin D-SUB connector, Male, with exposed pins
2) A soldering iron
3) Lead solder
4) Some short lengths of wire, preferably 20 AWG or smaller

All of these items should be available from your local electronics
store (such as Radio Shack), with the possible exception of the 25-pin
connector.  I've located one at DigiKey (http://www.digikey.com), they
offer quick service and great prices:

Part #A-2045ND, 25-pin Male D-SUB solder cup, USD$3.47 
So now comes the harder part, which is building the connector.  

1) Cut 5 short lengths of the wire and strip the insulation off of the
ends of the pieces.  The insulation exposed should be about a quarter
inch or so.

2) Preheat your soldering iron.  If your iron is new, coat the tip
with a little bit of solder by melting some on and then wiping clean
with a wet sponge (do not use this sponge for anything else
afterward!)  You should then "tin" the ends of the wire by heating
them with the soldering iron and then coating the ends with solder,
just enough to let some solder soak onto the wire.

3) Examine the exposed back end of the connector and locate each pair
of pins that need to be connected.  Most modern connectors have each
pin numbered, but if not you can locate pin #1 by looking at the
RIGHTMOST pin of the TOP row.  The top row has 13 pins and the bottom
has 12.  Remember this is looking from the BACK of the MALE connector!

4) Using the table above, solder the end of one wire to the solder cup
for pin #2.  Apply the soldering iron to the cup and heat it until you
can flow some solder into the cup.  Then insert the end of one of the
wires and hold the iron there until the solder flows around the wire. 
Remove the iron and hold the wire until the solder cools and
solidifies.

5) Take the other end of the wire and repeat the process on pin #15.

6) You have now connected Pin #2 to Pin #15.  Repeat this process with
the other 4 wires.  Pin #13 to Pin #1, Pin #12 to Pin #14, Pin #10 to
Pin #16, and Pin #11 to Pin #17.

After all the pins have cooled you should have a working connector. 
You may want to wrap the connector in electrical tape, or perhaps buy
a connector shell to protect the wires and keep them from breaking
off.  You should never pull on these wires to disconnect the connector
from the PC, use the shell of the connector instead.

I hope this helps you fix your parallel port, and thanks for using
Google Answers!

terms and websites used:
parallel port lookback checkit
www.digikey.com
nelson1805-ga rated this answer:5 out of 5 stars and gave an additional tip of: $5.00
Very quick answer and i had a spent all most a day trying to get the
answer, very impressed will use again if i get stuck

Comments  
Subject: Re: Loopback Tester
From: koz-ga on 06 Nov 2002 09:54 PST
 
Thanks, nelson1805!  I'm glad that I could help.

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