Can't connect Cisco SG300 console mode after test all community tips

[it salpa]

Good morning, 
we have to reset the password of our switch and we cannot physically reset it because there are configurations saved on it.
We looked at all discussions before contacting you but are unable to get the communication between putty and the console to work.
We use
1) startech DB9 RS232 Serial Null Modem F / M cable (SCNM9FM2MBK) +
2) final M / F adapter +
3) prolific pl2303 as a db9 / usb adapter.
The drivers of prolific were installed successfully, the device was first tested with settings 9600/8/1 / none / none and later with 115200/8/1 / none / none but without success as suggested by the various discussions. I'm pretty sure this last configuration is correct because the console responds to us, but it uses weird graphic signs, see image below.

[Flavio Miranda]

You should test your console connection in a different devices first. If work with a different device then you can be sure that the problem is not about cable, driver, adapter, etc. Unfortunatelly most of problem seeing on this scenarios is not on the switch itself.

 The truth is, if the problem is on the switch side, then you have a big problem as you are locked out outside. If that is the case, then unfortunatelly the only way out is factory reset the switch and start over.

 Hopefully  you have a backup. Although buid this switch from scratch is not that difficult.

[balaji.bandi]

too many converter, get cisco cable simple one and test.

[it salpa]

is not possibile. i don't have cable db9f db9f, i try to remove usb/db9 cable and connect  a startech DB9 RS232 Serial Null Modem F / M cable (SCNM9FM2MBK) + final M / F adapter into COM serial port on desktop computer but it doesn't recognized in any mode.

[balaji.bandi]

is this worked for any other device ?

[it salpa]

no, it didn't even work with a direct cable without adapters