S5 135U PLC to programmer communication

We are using S5 135U with CPU 928 and TTY converter for programmer communication purpose. This TTY converter is working with PLC com port internal supply. Now the communication problem is raised. I checked this TTY converter with another PLC. It is working. So I confirmed that PLC COM port is not working. This TTY converter was newly purchased. Old one is worked with external supply. It is worked for almost 10 years.

Now I need following clarifications:

1. Can siemens repair this COM port?

2. Can I use any interface module for communication purpose?( We are using CP143 with sinec H1 for MMI communication)Ex: PG submodule etc.,

I am a little confused, you say it worked then did not?
or are you saying the old one worked with external supply but this one does not using port supply?.
Also did you try it with a 135 processor or a 115?
I know that the TTY converter supplied by siemens did not work on the 150 without a seperate supply, also it could be only the supply that is faulty try using a powered version if possible & not rely on the plc supply.
I'm not sure that Siemens will now repair this processor now but there should be a number of companies out there that specialise in siemens equipment repair.

Sir,

OLD TTY converter is failed. Then new one purchased. I worked with new one twice. After that Communication not established. So I tried with PLC115H. TTY converter is working. So, I assumed that COM port of 135U is faulty.

In a tty port there are two current loops.
A good S5 com port has steady 20 mA DC (or less, typical 16 mA) for both the loops.
Check the inlet current at pin 13 (CPU RX) and out current at pin 19 (CPU TX) while the tty converter is connected.

Idon't know if Sie repair that old CPUs, The com interfase is a very small card soldered to mainboard, may be that card is equal in a new small cpu S100 for example.

Sir,
can you provide pin out of TTY com port?

"TTY com port?=
my post #4 was for a 25 pin port.

25 pin port http://www.plctalk.net/qanda/attachment.php?attachmentid=8093&stc=1

15 pin port http://www.plctalk.net/qanda/attachment.php?attachmentid=8094&stc=1

in a 15 pin port the current loops are 6-7 (cpu transmit) or pin 2-9 (cpu recive)

Have you used externsl TTY convrtor with 135U?

Because I believe it doesn't work with 135U PLC only?
If you have PG615( with power supply) or siemens PG720, Field PG try any one of this.