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Hardware, Cabling, Installations / Failure to Boot using 12vdc Power - Possible Cause and Solution
« Last post by N3AE on 2024-05-09, 22:10:00 »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.
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.