I have 2 indicators for the voltage, the original from Socata in the centre stack which as color bands and a few numbers on the edges of the color bands and my G2. I took out the memory card from my G2 to look at the logs of the last flights just to discover that the box stopped to log data somewhen in early 2016, so I won’t see there whether the voltage was fluctuating. I might need to download the logs from my Avidynes maybe there I could see this happening.
For sure I saw multiple light flickering. The G2 screen dimmed momentarily. This was not the case for the Avidynes. The annunciator lights also flickered and the Alt light came on at least twice with full throttle.
The bitch is that all of this does not happen on the ground.
Can it be reproduced on the ground with the engine running?
Hello Placido,
not TB20 but I had a very similar thing happen to me twice when the radios and other electrics started to act up. Both times it was the voltage regulator of the alternator. After a change of it the problems subsided.
Unless some electical cable became unstuck when they changed the magneto, I don’t see how this could happen out of the magneto unless, as it’s been suggested, the magneto was not grounded as required.
Voltage fluctuations would be my guess as well.
The cheaply made voltage regulators used in aviation are not properly sealed. I’d replace it and in case that does not fix the problem, you have a voltage regulator spare which will come handy eventually.
I once had an issue with a total TB20 avionics avionics failure, that was caused by a faulty voltage regulator, and followed by a faulty over voltage trip. The latter problem caused many boxes to blow up.
The voltage regulator was rather like the one on my 1946 Ferguson tractor
The thing is that IF the battery is in a working condition AND charged AND remains connected to the alternator output, the bus should not dip below about 23-24V even if the alternator output disappears completely. And no “24V” avionics should drop out at 23V or anywhere near as high as that.
Admittedly there is some crap out there but if the said kit works on the ground before you start the engine then it must be working OK in the 23-24V range.
Overvoltage is a different issue (that is what blows up avionics – a faulty voltage regulator WITH a faulty or missing overvoltage trip) but most avionics are OK up to something like 35V.
The TB20 voltage regulator is the Lamar electronic (pulse width modulated) type, not the old mechanical-contact one, and AFAIK this is true for all TBs.
So I think something else is going on. I would start by checking that the bus voltage behaves properly and stabilises at 28V when the engine is running. Then check all accessible connectors for loose wires.
And it is feasible to fly a plan with an oscilloscope connected into the cigar lighter socket, to check for transients etc. If you see any big ones, it means the battery is dud or not connected.
The battery is less than a year old. When I turn on the master switch to start the engine the voltage indicator shows in the yellow it has never been in the green not even new. It cranks the engine quite well though.
The battery should show around 23.5V depending on the loading. When the engine is started it should go to 28.0V. If these are way off, these need to be investigated first.
The colour bands on the analog voltage indicator are not worth much. One needs to look at the digital voltmeter.
