# Printer suddenly stopped working, "could not open port COM3"

**URL:** <https://forum.lulzbot.com/t/printer-suddenly-stopped-working-could-not-open-port-com3/2005>\
**Category:** Hardware\
**Created:** [July 16, 2015, 12:39am UTC](https://forum.lulzbot.com/t/printer-suddenly-stopped-working-could-not-open-port-com3/2005 "2015-07-16T00:39:02Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![thecelery](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.lulzbot.com/thecelery/32/9228_2.png) [@thecelery](https://forum.lulzbot.com/u/thecelery)\
**Post date:** [July 16, 2015, 12:39am UTC](https://forum.lulzbot.com/t/printer-suddenly-stopped-working-could-not-open-port-com3/2005/1 "2015-07-16T00:39:02Z")

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My Kittaz has been working flawlessly (aside from my own sloppy calibration issues) for over 6 months now. Now all of a sudden pronterface refuses to connect to the printer. It had just completed a print maybe an hour before - I disconnected it, let it cool off, set up for another print, and that’s when it refused to connect. It gave this error message:

> [ERROR] Could not connect to COM3 at baudrate 115200: Serial error: could not open port COM3: [Error 2] The system cannot find the file specified.

A cursory google search suggests the problem might be either a port issue (seems unlikely since I had just been printing an hour before), or the voltage regulator in the Rambo might be fried. The Rambo’s LEDs light up when turned on - I’m not very experienced with electronics, can anyone tell me how to diagnose the source of the problem?

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**Author:** ![piercet](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.lulzbot.com/piercet/32/12_2.png) [@piercet](https://forum.lulzbot.com/u/piercet)\
**Post date:** [July 16, 2015, 1:24am UTC](https://forum.lulzbot.com/t/printer-suddenly-stopped-working-could-not-open-port-com3/2005/2 "2015-07-16T01:24:45Z")

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Your USB port may not be com 3 anymore. You can check port assignments from device manager, or just try ports 4 through 9 until it connects. 1 and 2 should be system reserved. If none of them work it could be a hardware issue. Also check any USB hubs.