Sunday, May 20, 2012

WH-00036 Pins NOT Swapped!

This is an update to a previous post that did not contain the word "NOT" in the header.
When the electric diagram was released a guy on VAF found a discrepancy between the plans and reality and assumed that something was wrong with the wiring harness. After reading his post I checked the plans, compared reality and also found it at fault. However, when I fired up the Avionics today, I found that reality was obviously in order and the electric diagram must have a problem instead.
I refuse to dig deeper into the problem which is clearly a job Van's should do, but I traced it thus far: The Fuselage plug has two pins controlling the PTTs. Pin 1 should be connected to the Pilot PTT and Pin 3 should be the one hooked up to the Co-Pilot PTT. This is also what you can read from the electric diagram if you just look at the plug connection between the Fuselage pug and Van's Black Box.
If you follow beyond that point and route the connection to the actual switches, things get confusing quickly. It turns out that in the current plans the Pilot PTT from Pin 1 is effectively connected to the Co-Pilot PTT Switch. The same swap goes for Pin 3 which ends up at the Pilot Switch. However, the pins are indeed correct and what must be wrong is the naming in the electric diagram.
How I know? Well, I tested the radio and the Co-Pilot PTT triggered the pilot's voice to transmit and vice versa. I swapped them back and verified that now everything is working fine. The fact that the modulation on transmit is very distorted I contribute to the strong signal and the receiver being way too close to the transmitting antenna for now.

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