View Full Version : Cobra 138XLR No Power Output

11-17-2021, 12:57 PM
I have a Cobra 138XLR from the late 70s that I bought brand new. Under the guidance of a friend, I modified the radio. My friend past away in 2015.

The mods are: Unlocked clarifier. 120 channels with an add/subtract feature to navigate to a channel above or below the display channel. I installed two single pole six position rotary switches and made use of the PA/CB switch. I do not recall any other switch modifications. The 2 additional switches I added are disguised as the tone control and the dimmer control. The original knobs from those controls were drilled out to fit the six position switches. I also increased the power output internally then spread it through the 120 channels as best as I was able. Looking at this thing today 45 years later, I guess I had lots of time on my hands and it looks like I did a fairly good job. I will post some pictures when I am able but it is a piece of work for sure.

Around 1994 I put this radio in the closet because it failed to produce any power output. Well I pulled it out today to have a look. All the wiring and solders look good. I put power to it and the display is working. The relay kicks in when keyed up but no power out and no signals received. I am using a dumby load and power meter. I do not have a frequency counter unfortunately that was loaned and never returned.

I am not an expert by any means with this stuff. My best friend and designer of this modification would be best suited to help troubleshoot but he is no longer with us. I can solder very well and troubleshoot with guidance. Any help to repair this radio will be appreciated. Thanks in advance