Com 1 Issue

[ccdubs]

Hi,

I'm not exactly sure how but I think I may have damaged com 1 on a T100MD. I think an overvoltage may have occured.

What components should I try changing to get it working. I have another "spare" PLC that I can canabalise.

Thanks

[support]

The active components on COMM1 are the PN2222 and 2N4403 transistors. I don't suggest removing the transistor from a good "spare" PLC to put into a bad one. You should be able to buy the transistor quite readily from most electronic components seller such as digikey or mouser.

[ccdubs]

Thanks support.

I don't have a PLC in front of me, are the locations of these compontents obvious? I wouldn't want to replace the wrong component if there is more than 1.

Thanks.

[support]

The are to the right of the COMM1 port. If you are using T100MD888+ or T100MD2424+ then these are the only components. On the T100MD1616+ there could be same components on the analog circuitry so you do want to trace the circuit to make sure that the transistors you are replacing are for the COMM1 port.

[ccdubs]

Well I finally got around to trying this but it made no difference.

Any other suggestions?

I thought I would try the 485 port as I found my serial port driver had the ability to switch over to 485. However I have no idea which pins to use on the DB9 socket. Is there any standard for this?

[support]

There is no standard for RS485 on a DB9 socket. Therefore you will have to contact the maker of the RS485 adapter to find out what pin is the + and - for RS485.

On the T100MD+ PLC it is only a two pin screw terminals and the connection is stated on the installation guide or the User's Manual.

[ccdubs]

OK thanks.

In the mean time is there anything else I should look at replacing? Will testing that RS485 works prove anything?

[support]

If your RS232 port is damaged it is often either the PN2222 or 4N2203 that are damaged and these have to be replaced. In some rare occasion the CPU pin could also be damaged and that would require a replacement of the CPU.

If RS485 works it just means you can use it for programming/monitoring and prove that the PLC CPU is alive and working. However it doesn't do anything to resolve the RS232 port if it is already damaged.