What we found was that the internally wiring of the 811 was completely inexplicable. Documentation on the 811 was found in the museum's archives, and the wiring was significantly different than indicated. As wired, 120VAC was applied directly across the vane switch that closes when it sense airflow across the deflection transistor assemblies. As soon as it closed, it welded shut, and tripped the breaker. We never found out why the 811 was wired that way. We're pretty sure that it wasn't supplied by the factory that way, and that someone did a field modification, but we couldn't make any sense of how the modified version could have been useful for anything. We rewired it to factory spec, replaced the vane switch, and it has worked properly ever since.