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Marv, since you indicated an interest, here's what I found, and a couple of lessons learned.
Power sys schematic.jpeg
Lug connector.jpeg
Review, for those interested:
-- After 150 hours of trouble free flight, Alt 2 started kicking in intermittently even though bus voltage was 28V or higher. Replaced regulator 2, problem disappeared. 15 hours later, problem reappeared.
Question: Why did original and replacement Regulator 2 work okay at first, then slowly inch up in regulated voltage?
Answer: The lug connector at the voltage sense input on Reg 2 was crimped on the wire insulation, not on the stripped copper conductor. The copper made a "casual" connection to the lug that slowly deteriorated; as the connection deteriorated, resistance increased and the voltage delivered to Reg 2 dropped; so Reg 2 sensed lower voltage, and began kicking in at higher and higher actual bus voltages. Also, when I replaced the regulator, the physical agitation of disconnecting and reconnecting the line temporarily improved things, making it look like the regulator swap had fixed the problem. Fix: Crimp the connector at the proper location. Time: 10 seconds. Cost: Nada
New and Re-learned lessons:
1. Bill Bainbridge at B&C Electric (manufacturer of Alt 2 and both regulators) was highly knowledgeable and very helpful. He should start a radio show called "Wire Talk" with Arc and Spark, the Current Brothers. Just based on my verbal description over the phone, he narrowed it down to two wires (shown in brown on the diagram) and said "check the connectors". Bingo -- right on, Bill!
2. Bad connections can manifest just about any weird behavior, not only open circuit.
3. Wishful thinking cost me a few hundred bucks for a new regulator I didn't need, a second round of irritation, and didn't get me out of having to use my brain after all. Now the Garmin bonging has stopped and I can go back to smokin that stogie and watching the scenery roll by.
Charley Brown
Legacy RG #299 200 hrs
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