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Final Approach
I took my Sandel to the avionics shop today to have its lamp replaced, as although by hours it is only halfway through its recommended life, Sandel does recommend replacing the lamp every year and it has been over a year since mine was last changed. The lamp change set me back about $250, but seemed to be routine. Then: after setting a course on the GPS (a 480) back to home base and taking off, I noticed the Sandel CDI needle quivering and then snapping to center, very abnormal. To test whether it was indeed malfunctioning, I flew away from my course at a right angle. Same behavior. The 480's NAV page showed that the GPS's deviation information was reasonable, and its HSI-like display showed correct deviations. Only the Sandel was malfunctioning.
I later determined that the left/right deviation indications are also faulty in VOR mode, and the to/from flag was missing from the display. These items also fail to test properly upon powering up the avionics. The GPS tests the functions but is completely unaware that the Sandel is not displaying any of the commanded functions (CDI centered, full & half left/right, VDI centered, full & half up/down, to/from flags on and off, all these commands are shown as tested on the GPS, but have no effect now on the Sandel -- very different from when I took off from home this morning).
The Sandel installation guide shows that all of the affected functions involve inputs carried on adjacent pins of connector P1 (the last 1/4 of the length of the connector on the opposite end from pin 1). So I'm thinking, hopefully, that it might just be a seating problem with the Sandel. Just wondering if anyone else has had a similar experience, and what the problem ultimately turned out to be.
I later determined that the left/right deviation indications are also faulty in VOR mode, and the to/from flag was missing from the display. These items also fail to test properly upon powering up the avionics. The GPS tests the functions but is completely unaware that the Sandel is not displaying any of the commanded functions (CDI centered, full & half left/right, VDI centered, full & half up/down, to/from flags on and off, all these commands are shown as tested on the GPS, but have no effect now on the Sandel -- very different from when I took off from home this morning).
The Sandel installation guide shows that all of the affected functions involve inputs carried on adjacent pins of connector P1 (the last 1/4 of the length of the connector on the opposite end from pin 1). So I'm thinking, hopefully, that it might just be a seating problem with the Sandel. Just wondering if anyone else has had a similar experience, and what the problem ultimately turned out to be.