Serial port can't send data

[RiP]

I had to create a new topic for this problem since it has totally changed.
Following the old topic: http://www.amiga.org/forums/showthread.php?t=71731&page=2

A2000's serial port receives data without any problem but can't send.

According to the previous topic, I changed Paula/CIAs but they didn't help.
I also checked the traces and they were fine but noticed about these too:

Pin7&8 of U304 are connected to each other and Pin7&14 of U305 are connected to each other too :confused:
-12V and +12V between pin1&14 of U304 is ok (24V) and +5V between pin7&14 of U305 is ok too (5V)
http://www.amigawiki.de/dnl/schematics/A2000_R6.pdf

I'll try the software solutions from the old topic and will post here.

[RiP]

CTS not high?

High? I just know that CTS trace was ok from U305's pin4 to COM's pin5.
I was changed U304 before but didn't help. Should I replace U305 it too?

As gertsy said, it's probably CTS

With that said, have you tried injecting a pulse into Pin 9/10 of U204, and looking for output at the TXD pin of the serial port? It should be inverted. If it is, you know for sure the signal path is fine.

Injecting a pulse? I was checked the traces between Paula/CIA U301/U304/U305/COM and they were fine except what I wrote in the first post.

[RiP]

Sorry didn't read the first thread. (That's Me...).  I just remember once doing a whole lot of troubleshooting on a serial port and cable just to find out one of the pins/sockets(cant remember which) had recessed itself (had been pushed back in the plug/socket) and was not connecting.  I'm guessing you have a breakout box and have tested the continuity of each necessary line to the back of the serial socket in the 2000?  You do have a multi-meter or continuity checker? When you say "checked the traces", what does that mean?  

Just an aside: I think I found an error.  The schematics you posted refer to the "Infernal" serial port.  That one's always going to cause problems.  

Keep up the trouble shooting.

No, I'm using DB25 external port. The old topic was about internal header and that's why I created the new one.

[RiP]

Pin 8 (output) of U304 has connected to Pin 7 of U304 (ground). Isn't it strange?

[RiP]

If you're measuring short with the Amiga off, then yes, it is strange. Have you tried performing the same measurement after removing U304 and/or EMI326? U304 is prone to failure.

I removed U304. It seems C315's legs are connected together.
Will capacitor's legs connect together if it fails? :confused:

[RiP]

Remove C315, check again - If still shorted, remove EMI326, check again. If still shorted,  remove CN305, check again. If still shorted, reinstall CN305, cut the trace at Pin 8 of U304, and run a wire directly from Pin8 of U304 to Pin 2 of CN305

Edit: Basically remove everything in the electrical path of the TXD pin until the short clears, then you know what your fix will be

I was removed U304 before and it wasn't the problem. Later, I removed EMI326 and the shorted problem solved but EMI326 was fine too out of the board when I tested its pin2.
Then put it back and there was still no problem until I turned it on and problem happened again. I even disconnected the EMI326's pin2 but it didn't help. TXD pin is still connected to the ground
Wonder why it happened after turning on, maybe a cap was charged. I'll try to remove C315 next time.

[RiP]

Wow, the problem was C315. It's working fine now. Thank you all :laughing: