Cisco 7936 Conference station - Red LED blinking and no LCD display after power on

Unanswered Question
Aug 3rd, 2010

We have three Cisco 7936 Conference station. These phones are working fine just 2 days back all three 7936 stop working, on all 7936 RED led is blinking and blank LCD display. Even after restarting it is giving the same problem right after powering on. I am sure it is some hardware problem. I want to know if some one face these problem before and whether the problem is with power adapter or phone  and why all 7936 get problem at same time ? I don't have any spare power adapter or 7936 apart from these 3 pair to test and know the exact reason of problem, and these three phones with three adapter not working with any combination.

I have this problem too.
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jweekers Wed, 10/13/2010 - 23:27

I have the same problem.  Did you ever find a solution?


muhammadzubair Thu, 10/14/2010 - 06:03

Power the ip phone off and on. During the reboot, press and hold the  hash key (#) during the entire reboot.  The phone will display "Reset  key sequence detected".  Enter 123456789*0#, followed by 2 to erase the  entire config.


dougsetley Mon, 10/18/2010 - 13:01

I am having the same problem. However holding the # button does nothing. I plug in the phone, I get a tone that you would get when you power it up and the red lights and they (the lights and tone) just pulsate (off and on) every second or so with nothing at all on the screen.

Brad Martin Mon, 10/18/2010 - 13:10

Our red blinking light issues have all been related to power supplies. Not sure what makes them fail but have had several go bad. The phones have issues with background noise but once I find a good power supply, I can boot up all the phones that have the red blinking light issue.

jweekers Mon, 10/18/2010 - 18:45

Thanks, it does feel like a power supply thing.  I will order a few new ones and cross fingers I still have some good phones.

Note to any interested parties that the Hold the # instruction is to reset a 7940 etc series phone to factory defaults.  If you want to do this with a 7939 You need to watch for the prompt during bootup to change the config and hit the menu button. There is a factory default option in the list - assuming your phone stays up that long!

natasha_mckenzie Fri, 10/29/2010 - 07:03


Was your issue solved after replcing the power supply?

I have a 7936 that when powered up the red lights flash and it goes through the wierd pulsing noise, which does stop after a few minutes, but it then does the same again if the power is disconnected and connected again.

Thanks in advance

dougsetley Fri, 10/29/2010 - 07:36

Yes, replacing the power brick did the trick, however, its not easy finding a power brick by its self.


Doug Setley,

IT Desktop/Telecomm Support (651-201-8055)

Technical Services Unit |Minnesota Management & Budget (MMB)

“Plan for the future because that’s where you are going to spend the rest of your life.” (M. Twain)

nlaxmidas Wed, 02/16/2011 - 09:09

Does anyone know what the Part No('s) is/are for the items needed?  Also, is it the "Cube"

part that needs replacing or the Power Adaptor?

With thanks, Nitesh.

jweekers Sun, 02/27/2011 - 17:36

New power supplies fixed our problems, but unfortunately, the 7936 are end of life and you can no longer buy the power kits.  The power supplies were never available on their own and you had to get the full kit - with the cables etc.


lbrown-amigoid Thu, 03/17/2011 - 12:39

If your 7936 has flashing red lights, no LCD screen, clicking, and will not initialize, its a bad power supply.

A picture is worth a thousand words, so here is a short video clip with the speakerphone power supply failure symptoms.

This was tested and verified on 3 different speakerphones. Please rate me if this was helpful.

Message was edited by: lbrown-amigoid (added the video clip)

nlaxmidas Mon, 05/09/2011 - 08:57

Ibrown - this is a very similar issue to what we are seeing on the 7936g.

We've now managed to purchase a replacement power supply/cables etc and have replaced the faulty equipment. All seems well -red lights all gone!

Thank you, Nitesh.


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