[TG] [TG11] st4000+ control unit voltage

[Tom - Raymarine - Moderator]

Hello timpa,

The drive output from almost all of our pilots is what's called pulse-width modulated (PWM), which means that the drive voltage is pulsed at a high frequency (tens of kilohertz) in order to provide more control over drive movement than a simple 12V would give. The pulses are actually 12V, but a multimeter is too slow to be able to pick up the peaks and only shows an average voltage. 5-6V is a normal voltage measurement for the drive output of a 12V pilot.

If the pilot's putting out ~5V average (0 - 12V pulsed output) and the motor's not responding but does to a direct 12 supply, then perhaps counter-intuitively that's actually a sign of a worn and failing motor. You can check this by connecting a different 12V motor or something like a 12V car indicator globe or incandescent nav-light globe to the ST4000's output in place of the pilot motor. I suspect you'll find that that other load works ok. I've seen failing motors work on direct 12V and not work on pulsed pilot output many times, and it's always been a motor problem rather than a pilot problem. If it were a pilot fault then you'd almost certainly see a flat 0V on the drive output.

Regards,
Tom