# USB to Serial Adapter Troubleshooting

- Use a "real" RS-232 serial port, if available, in preference to a USB to Serial Adapter.
- Verify that the USB to Serial Adapter's device driver is up-to-date. To determine the currently installed device driver's version:
  - Plug the USB to Serial Adapter into a USB port on your computer
  - Open the "Start" menu
  - Right click "My Computer" or "Computer"
  - Select "Manage"
  - In the Computer Management left pane, select "Device Manager"
  - In the right pane, select the "+" next to "Ports (COM & LPT)" to expand the Ports list
  - Double click the COM port entry for your USB to Serial Adapter. The Elecraft KUSB appears as a "Prolific USB-to-Serial Comm Port".
  - The "Driver" tab contains the "Driver Version". If you're using an Elecraft KUSB or other Prolific chip set USB to Serial Adapter cable, this Driver Version must be version 2.0.2.1 or later, and version 2.0.2.8 or later is recommended.
- If your Prolific device driver is earlier than version 2.0.2.1, update it to the current level by visiting the manufacturer's support web site. The Elecraft KUSB driver can be updated from http://www.prolific.com.tw/eng/downloads.asp?ID=31. The chip set in KUSB units sold before mid-2010 is a Prolific Technology, Inc. PL-2303.
  Recent KUSB USB to Serial Adapters labeled "Sabrent" may use an FTDI chip set, and the driver diskette accompanying the KUSB contains suitable device drivers.
  Use the Windows Device Manager to determine the chip set used in your KUSB.
- After installing the new device driver, take a moment to verify that it was actually installed by viewing the Driver tab again. If the new driver did not install, it may be necessary to uninstall the old device driver before installing the new driver. If a Prolific Driver has already been installed, you may need to run the new driver installer twice. The first "installation" seems to only remove the old driver. Run the installer again to install the new driver.
- Try a different USB port on your computer.
- Try a different USB to Serial Adapter.
- Try a different computer. Some combinations of USB to Serial Adapter and USB port are more reliable than others. For example, some laptop computers may not provide sufficient power to USB devices for reliable communications.
- Try changing the KX3's RS-232 data rate to 38,400 bits per second using the KX3's CONFIG:RS-232 menu selection. Firmware is sent at 38,400 bit/s, and setting this speed at the start removes the need for the KX3 Utility to change the KX3's RS-232 speed.
- Some users have found that their combination of computer and USB to Serial Adapter is much more reliable at 38,400 bit/s than at lower speeds.
- One user reported that his USB to Serial Adapter did not work well when connected through a USB Hub.
- Some users have found better results with separately powered USB hubs rather than those that receive power from a USB port.
- One user of a USB to Serial Adapter found it helpful to add a ground connection between his laptop computer and KX3 chassis.
- A laptop computer's USB port may work more reliably if the laptop is powered by a power supply rather than its batteries.
- One user reported severe communications errors that prevented successful firmware load when he used a switching power supply. When he switched to a linear power supply the RS-232 communications were rock-solid. Connecting the PC ground to the KX3 ground to the switching power supply's metal case solved the problem. The switching power supply did not have a ground connection from the wall plug.
- One user reported difficulty loading firmware when his PC was plugged into one wall power outlet and his KX3 power supply was plugged into another. Plugging both his PC and KX3 power supply into sockets on the same wall outlet eliminated the problem.
- Before loading KX3 firmware through a virtual port associated with a microHAM microKEYER, microKEYER II, MK2R or MK2R+, change the microHAM USB Device Router's Radio type to "none". (TU W4TV). If you are unable to load firmware through a microHAM device, use a USB to Serial Adapter or a "real" RS-232 cable. Neither microHAM nor Elecraft recommend loading KX3 firmware through the microHAM Router (the PC software used with microHAM USB devices).
- Disconnect all KX3 cables and wait 60 seconds to allow voltages to decay enough for the KX3 microcontroller to completely shut down. One user discovered that a cable connected through the KX3 back panel "12V DC Out" RCA connector provided enough voltage to keep the KX3 microcontroller from resetting.