How to reset a Cisco 1720 ... that has the console port locked

Wow there's some help right on EE:
https://www.experts-exchange.com/questions/23222850/Resetting-a-Cisco-1700-series-router-to-factory-settings.html

However, it appears that even that won't work based on what you are getting, because you should be able to get a password: or user: prompt when you hit return.

Have you tried telneting into the box?  The ususal default password in any event is "cisco"

Here's some general help on that box too.

http://www.cisco.com/en/US/docs/routers/access/1700/1720/hardware/installation/guide/trbshoot.html

Also, other cisco boxes have a reset button, which when held in during power on will wipe things to factory.  I don't know if that box has such a button or not.

Step 1 Connect an ASCII terminal or a PC running a terminal-emulation program to the CONSOLE port on the rear panel of the router. Refer to the section "Connecting a PC" in the "Installing the Cisco 1700 Router" chapter.

Step 2 Configure the terminal to operate at 9600 baud, 8 data bits, no parity, and 1 stop bit.

Step 3 Reboot the router by pressing the power switch to the OFF position, then to the ON ( | ) position.

tep 5 Record the setting of the configuration register. It is usually 0x2102 or 0x102.

Step 6 Record the break setting.

"Break enabledbit 8 is set to 0.

"Break disabled (default setting)bit 8 is set to 1.

Note To enable break, enter the config-register 0x01 EXEC command.
Reset the Router

Step 1 Do one of the following:

"If break is enabled, go to Step 2.

"If break is disabled, turn the router OFF, wait 5 seconds, and turn it ON again. Within 60 seconds, press the Break key. The terminal displays the ROM monitor prompt. Go to Step 3.

Step 2 Send a break. The terminal displays the following prompt:

rommon 2>


Step 3 Enter confreg 0x142 as follows to reset the configuration register:

rommon 2> confreg 0x142


Step 4 Initialize the router by entering the reset command:

rommon 2> reset


The router resets, and the configuration register is set to 0x142. The router boots the system image in Flash memory, and displays the following:

--- System Configuration Dialog ---


Step 5 Enter no in response to the prompts until the following message is displayed:

Press RETURN to get started!


Step 6 Press Return. The following prompt appears:

Router>


Step 7 Enter the enable command to enter privileged EXEC mode. Configuration changes can be made only in this mode:

Router> enable


The prompt changes to the privileged EXEC prompt:

Router#


Step 8 Enter the show startup-config command to display an enable password in the configuration file:

Router# show startup-config

tep 1 Enter the configure terminal command to enter configuration mode:

Router# configure terminal


Step 2 Enter the enable secret command to reset the enable secret password in the router:

Router(config)# enable secret gobbledegook


Step 3 Enter the config-register command and the original configuration register value that you recorded in Step 5.

Step 4 Press Ctrl-Z to exit configuration mode.

Router(config)# Ctrl-Z


Step 5 Save your configuration changes:

Router# copy running-config startup-config

Reset the Configuration Register Value

Once you have recovered or reconfigured a password

Step 1 Enter the configure terminal command to enter configuration mode:

Router# configure terminal


Step 2 Enter the config-register command and the original configuration register value that you recorded in Step 5.

Step 3 Press Ctrl-Z to exit configuration mode:

Router(config)# Ctrl-Z


Step 4 Reboot the router, and enter the recovered password.

Unfortunately, neither of the links were any help I had already been through those.

The issue is I can't get to any prompt on the console port.  I cannot use the BREAK command to get to rommon.  

I can telnet to the box, but the passwords were not documented.

The issue did turn out to be the USB/Serial adapter not actually sending the BREAK ... I swapped to a laptop with an actual serial port and suddenly everything worked as promised!  

Thanks!!