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I am not familar with Fadal details.
I believe you are talking about a problem at you CNC machine.
Do you know that your computer is good? Here is a test I posted on another question here.
If you go to
Following is a self-contained procedure that you can use to check your
PC hardware for both send and receive.
Assume COM1 is your RS232 port.
Make a connector that will jumper pin 2 to 3. You can also bring a wire
out from pin 5 and another one from the jumpered 2 and 3. Make pin 5
black, and pin 2-3 green. Two feet long is good. Call this a loopback
cable. Do not short black and green together.
Plug the loopback cable into the port to be tested.
In Windows pick
Connection Description should be displayed. If not pick FILE at the top
left and pick NEW CONNECTION.
Under name enter something like the following with the values you want.
This is just an identifying name. I do not know the length limit.
Select COM1 or whatever your port is.
Now enter your settings. APPLY, OK
Pick TRANSFER and CAPTURE TEXT
Now you have to specify a subdirectory and filename for the captured
text to be placed into. Then pick its START.
Next type some characters on the keyboard. These should show on the
screen. If no characters appear, then you have some sort of problem.
Pick TRANSFER again and pick STOP. Now look at the content of the
file to which you directed your capture. What you typed should show
up if the loopback worked.
The black and green pigtail wires are so you can look at the voltage,
or use the signal.
If you know that the PC RS232 works, then you can connect the these
wires to send a signal to your CNC, but you can not connect the TxD
from the CNC to this loopback green wire. With the CNC powered up try
transmitting data again to your capture file. If the data is correct, then
the CNC RxD input is not excessively loading the TxD output of the PC.
http://www.cnczone.com/forums/showthread.php?t=44526 (Fadal CNC 88)
and look at some of my posts you will find discussions on voltage measurements that may help identify the problem area.
Can you define what the pin connections are in the Fadal loopback test plug?
Also visit my web site