I was just able to resolve a similar issue...I have a FT 817 and a FT 818 and two Z817 tuners. I purchased the 818 new with a new tuner, the other set I got used through E Ham website. The Ft 818 and the tuner worked perfectly able to tune almost anything to the steady green LED. One day I noticed that the tuner would not tune at all on several bands, the 5 Red LED blinks indicating no RF. I checked the second tuner that I had never used and the same thing happened... Very frustrating......
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What I found........Of course check to see the CAT rate is set to 38400. Also Menu#42 repeater shift needs to be set on each band, read manual carefully, Set to "0".
Mine was set to 5 or 6 mhz. so when I tried to initiate a tune, the offset would try to Xmit out of band.......The radio doesn't show this. the tuner just fails to successfully make the radio Xmit. Once I figured this out both tuners perform as designed.....Big Shout out to Mark at LDG Electronics Tech Support as he was willing to spend a bunch of time with me on the phone trying to figure out what was going on before I found Menu #42 adjusting by band
