For some reason the 5500 and the LVB in my system got out of whack. It may have been when I switched from "450 degree azimuth" mode to "flip" (i.e. 180 elevation) mode. I don't know. But even after calibrating the LVB several times, it would not set the elevation to 180 and setting it to 90 degrees ended up something like 15 degrees off.
I took the LVB cover off to access the connections to the 5500, and discovered that far from sending an analog voltage of 2 to 4.5V to equal 0 to 180 degrees as the Yaesu docs say, the 5500 was sending 0V to 5.5 or so. A bit more work found that the LVB did not respond to much more than 5V. I assume that is the reference voltage on the A/D converter.
A look at the schematic on the 5500 found a pot that appeared to adjust the voltage to the LVB independently of the meters. There is zero documentation, but the back of the 5500 case actually has 4 pots: Max meter and Max output for both Az and El. So holding my breath, I turned the Max Output pot and sure enough the voltage to the LVB went down. I set the rotor elevation to 180 degrees (by eye) and then turned the pot till the LVB readout just started changing. Then I used the LVB calibration procedure to match that location to what the LVB thought was 180. Voila! 90 is now pretty good too.
In retrospect, this is not inobvious; however the fact that the Yaesu docs say 2V to 4.5V and the fact that the LVB was not responding beyond a certain elevation required some investigation. Hopefully this little post will save someone else from having to repeat the investigation.
73,
Burns, WB1FJ