Hi Alexandr,
'show tech all' does include 'show conf', but the .cfg is actually an XML file, which is the actual config file that the switch reads on boot. I'm thinking that there may be something strange in the config, so having the actual XML file that the switch loads the config from would be helpful. You can see the config file that was booted in the output of 'show switch', and you can TFTP this file off to a TFTP server.
If you do 'upload debug', this will also get the current .cfg file.
-Brandon