millner(at)me.com
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 Posted: Tue Nov 24, 2015 5:14 pm Post subject: Troubleshooting radio whine/noise on Cessna 182P |
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Charlie,
The problem is that you're not aware of how Cessna wired the regulator in this 182...
Instead of the OV relay interrupting the current path between the regulator and the field terminal as you propose OBAM folks usually do it, the OV relay and the alternator half of the master switch interrupt the power supply *to* the regulator, via the S or Supply terminal.
However... the automotive version supplies the regulator and alternator from both the S and the A terminal... and once the master is on, the A terminal is hot... so the Cessna OV relay and alternator half of the master switch are irrelevant.
So... an automotive regulator in the Cessna wiring diagram? The alternator is non-controllable... which could be a bad thing.
See attached wiring diagram.
Paul
http://www.secure4host.net/upload/files/Cessna_Alternator_Wiring.pdf
On 11/24/2015 11:18 AM, Charlie England wrote:
| Quote: | You do NOT want a Ford automotive regulator... it can cause an overvoltage situation that even an external OV relay cannot overcome (the automotive regulator sources regulator power directly from the alternator, and thus ignores whether the OV relay or alternator half of the master switch are providing power, or not.)
I can't make sense of this, as long as we're talking about an externally regulated alternator. Ford style regulators are flying in thousands of homebuilts safely (assuming that OV protection is used). As long as the wire to the field is interrupted, the alternator cannot produce power. Typical OV protection circuits either open the field lead or 'crowbar' it to ground, tripping the field circuit breaker (which breaks the field circuit). Either way, there's no way for the regulator to keep the alternator operating.
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