Failure to Boot using 12vdc Power - Possible Cause and Solution

[N3AE]

Just wanted to share what I found during some troubleshooting today.   I have a Control RCC, s/n 13824, that experienced difficulties booting when power was supplied through the 12vdc coaxial plug.  Initially it was fine but on a subsequent power-ups it failed.   Symptoms included no Green power LED with a steady Red and Yellow LED (above Mic connector), plus no ability to link to the internal web server. 

I discovered that the 12v jack on the PWB was mounted slightly askew such that the outer ring (negative) of the 12V coaxial power plus could/would contact the side of the chassis hole when inserted into the jack.  Looking at the PWB traces, it appears that the 12v negative is not necessarily connected directly to chassis but, like the positive supply, runs through an inductor in what amounts to a pi EMI filter.  So my assumption is that direct contact from the 12v negative to the chassis is not intended and causes issues.

Rather than mess with the jack on the PWB, I used a tapered reamer to slightly enlarge the chassis hole.  That solved the problem.

When assembled, you should see the 12v coaxial jack's plastic continuously around the circumference of the chassis hole and well centered in the hole.  If it's not, chances are that the outer ring of the coaxial plug will be in contact with the chassis even though the plug "feels" fully inserted.

We have a number of RRC-1258 MKII's running in our RACES setup and they have been very reliable.  Not a single glitch since being powered up in the fall of 2021.  This one had not been powered up since it was purchased.

[N3AE]

Well, not so fast.  After several days of behaving normally, this control RRC is back to its old tricks.  It was working fine, controlling the remote Kenwood TM-V71A and providing good two-way audio.  But after cycling power to the RRC it will not boot up.   On another good control RRC at power-up, I see a brief flash of the green power LED followed by a steady red and yellow LED on the mic connector for a few seconds.  Then the red and yellow extinguish and the green begins blinking until a TCP/IP connection is made.  On the problem unit, I see no flash of the green LED and the red and yellow illuminate immediately and simply stay that way.

Another observation:  If I power the RRC from the USB connector with 12v disconnected, the unit appears to boot up.  Red and yellow LED's extinguish after a few seconds and the green LED blinks fast, per the manual.  While in this state, if I then apply 12v power with the USB still connected, the red and yellow LED's turn on again, after a few seconds extinguish and the green LED blinks at a slower rate typical of waiting for a TCP/IP connection.  If I then remove the USB connector with the 12v still applied, the RRC seems to stay as it was in a normal state, with the red and yellow off and the green blinking slowly and turning steady on once a TCP/IP connection is made.   I can access the RRC over my web browser and all the configuration setup looks fine.  Interestingly, I can command "Restart Device" from the browser window and the RRC does successfully boot back up.  Once in this state, the control RRC works fine with it's radio partner RRC and a Kenwood TM-V71A. 

If I then drop the 12 v power, wait a bit and reapply 12v, the RRC goes back to a steady ON red and yellow with no green LED and I lose the TCP/IP connection.

If I reverse the whole sequence and apply 12v first followed by connecting the USB, the RRC stays locked with red and yellow on continuously plus no TCP/IP connectivity.

Tried several different 12v power sources with no change.  This problem looks like some sort of hardware-firmware timing issue.

Anyone see this behavior before and have a fix?  I have not tried reloading firmware yet.  It RRC already had v2.95 loaded out of the box.

tnx

N3AE