So a few weeks ago I took my repeater offline due to transmitter issues. I run a RKR1225 (rack mount version of the GR1225) and of course this repeater is known for its issues with burned out finals in the PA. At the time the unit was putting out .1W of its 25W of power. I didn't have time to pull the unit from the rack and disassemble the shelf so for a bit, out of wanting to protect components, I just shut the repeater off.
Fearing a PA failure I was in no rush to dismantle anything until I knew I could get the parts or ship it out to a shop for repairs. When the time came earlier this week, I contacted a shop who said I needed to confirm the PA had not already been replaced as they couldn't repair an already repaired amp. So I pulled the shelf from the rack and began to dismantle it so I could remove the radio body, however when I removed the TX jumper from the radio, I found that the coax had failed, separating from the connector. From just looking at it you couldn't tell, but everything, the center pin and the shield, had come apart and simply slid out of the end of the connector and rest in my hand!!
Concerned the PA may have been damaged because of this, I found a crap jumper I had set aside when I was given the double shielded jumper. I ran it through the meter and into a dummy load and behold, TX power returned to 25W! A little more testing, including the duplexer showed everything was working fine. I figured I would test the coax separately with a test meter for coax and sure enough it showed high resistance and feedback in the little 1' jumper.
In the end I purchased 2 jumpers, a bit longer than the one I was replacing as I believe the older one could have been pulled on during install. I replaced both the RX and TX jumpers with LMR240 coax and the result is that not only did the TX power come back, but the range extended a little bit as well.
This is just a reminder that even the simplest of things such as a jumper can mimic larger more costly problems. I believed it was going to be nearly $150 to repair the repeater and I even considered just replacing the unit with one that could run 50W on a 100% duty cycle. All I really needed was a $15 jumper to replace the one that failed. For those of us diagnosing issues for repairs we need to keep in mind that its not always the common problem causing the issue, and we need to make sure we always check the simple stuff we often overlook such as jumpers which are not a common failure point.