I am trying to troubleshoot a KR87 installation in an RV-6, and think I'm out of steps to try, short of taking it to a shop and having them open up the radio itself. Here's where I'm at?if anyone has any further ideas, it might save what little hair I have left!
1) Unit was installed and working properly for some time.
2) Unit started malfunction such that it would work at power-up for a little while, then quit.
3) Unit was sent to avionics shop and the power supply was replaced.
4) Upon return, unit would point at station if aircraft was pointed at station, but otherwise, was not accurate. (I don't have any better description than that, as I wasn't involved then). Unit, with indicator, was sent back to shop, and they "adjusted out an error of 30 degrees".
5) Unit was re-installed, and the indicator receives and points - but to the wrong side of the plane. For instance, with station at eight o'clock, pointer is at four o'clock. Front to back is right, left to right is reversed.
6) I became involved. Checking the pin outs (I don't have the install manual), there is a pin that is used to tell the unit if the antenna is on the top or the bottom of the aircraft. Confusing this would exactly match the observed behavior. It is supposed to be grounded for a bottom antenna, which is what we have. I checked the pin in the connector (airframe side), and it was NOT grounded - Ahah! We have a solution. I grounded that pin with a jumper, verified that all other connections were properly wired, and reinstalled the unit. Got the same results. I grounded and ungrounded the "top/bottom antenna" pin while the unit was on, and got no change whatsoever.
Conclusion - the unit (radio itself) is not recognizing the top/bottom antenna select jumper, so the problem has to be in the radio - possibly messed up when the radio was opened for the power supply repair. Which means it has to go back to the shop.
I hope someone can find a flaw in my analysis - I hate taking things to shops?..
Paul
1) Unit was installed and working properly for some time.
2) Unit started malfunction such that it would work at power-up for a little while, then quit.
3) Unit was sent to avionics shop and the power supply was replaced.
4) Upon return, unit would point at station if aircraft was pointed at station, but otherwise, was not accurate. (I don't have any better description than that, as I wasn't involved then). Unit, with indicator, was sent back to shop, and they "adjusted out an error of 30 degrees".
5) Unit was re-installed, and the indicator receives and points - but to the wrong side of the plane. For instance, with station at eight o'clock, pointer is at four o'clock. Front to back is right, left to right is reversed.
6) I became involved. Checking the pin outs (I don't have the install manual), there is a pin that is used to tell the unit if the antenna is on the top or the bottom of the aircraft. Confusing this would exactly match the observed behavior. It is supposed to be grounded for a bottom antenna, which is what we have. I checked the pin in the connector (airframe side), and it was NOT grounded - Ahah! We have a solution. I grounded that pin with a jumper, verified that all other connections were properly wired, and reinstalled the unit. Got the same results. I grounded and ungrounded the "top/bottom antenna" pin while the unit was on, and got no change whatsoever.
Conclusion - the unit (radio itself) is not recognizing the top/bottom antenna select jumper, so the problem has to be in the radio - possibly messed up when the radio was opened for the power supply repair. Which means it has to go back to the shop.
I hope someone can find a flaw in my analysis - I hate taking things to shops?..
Paul
