[79FT]: Building Things
tested fuselinks, measured loads, removed and diagnosed turn-and-slip indicator
|Jun 18, 2019
|[Chickenhouse Charger] Electrical Rebuild
|6781G, MA5 Charger, electrical, experiments, research, instruments, soldering
Finally, doing some actual work on the airplane, and having fun! And I decided to start logging time.. because, why not!
I like marked wires. I used to be a networking guy, and I was very meticulous about marking every single wire in my cabinets, so that I knew exactly what was plugged in where.
It took a bit of upfront time, but saved a bunch of it later on.
So naturally, I was planning to do the same on the Charger, and, more importantly, make it look professional.
Thanks to living in this day and age, that is simple. No, I'm not gonna pay someone to laser etch my wires - that's a cop out :). It's like paying someone to paint your plane.
Instead, I have researched and found a perfect label maker - Brady BMP21 (not including a link here because it will probably go dead after some time... just search for it). This thing has 3:1 heatshrink tube cartridges.
The proverbial coupon
Prior to shrinking
Prior to ripping the old wiring out, I wanted to take some real life load measurements with various things turned on, so that I don't get any nasty surprises.
But this plane has no ammeter... damn. I searched around, and found this little doodad:
Hall Effect ammeter
Very nice. It basically measures current on the wire passing thru this big white ring using Hall effect. Very cool! No need to splice into the battery leads and install a temp shunt.
So, I rigged it up and took some numbers.
So couple interesting things here. I think the x-der number is too low, but it wasn't being interrogated, and I can't make it be interrogated without flying the plane or using a transponder tester which I don't have. Also, Master On is too high seemingly... Will need to double check later and isolate things (master solenoid, hobbs, voltmeter, voltage regulator, fuel gauge) if I care enough - I don't think I do. Also, fuel pump is too low seemingly. Need to double-check the spec.
And then, I could not turn on the Turn-Slip Indicator...
Sad, sad indicator... see, it's long. And it's wire connector is sticking out. And it's right behind the front seat's headrest, and there's just not enough room for it, and the connector.
So whomever put it in... did this:
Sad, sad wiring
It's hard to see; but basically, those wires are bent "down" at a very sharp 90 degrees angle. Notice how he just used pins without the actual connector. The distance between them is tiny! I am surprised they haven't shorted over all these years. I really am.
Initially, I thought the gauge didn't turn on because that wiring was all bust up, so to test it, I decided to pull it out.
On the bench
I cut off the wires with those pins on them to hook it up to my testing battery... hmm.. but I needed some leads! Well, I was gonna make a bunch of various test leads - so this is as good a time as any! Man, I love soldering...
I long decided to make a bunch of leads with "passthru" banana plugs on one end, and something (a crocodile clamp, a battery clamp, a ring terminal) on the other. This way, I could mix and match, and plug them into my multimeter; daisy chain, and have multiples depending on what and how I needed to hook up. I had all the bits (clamps, crocodiles, banana plugs), and even got a roll of very nice super flexible silicone coated probe wire.
Components, and the battery clamp crimped on
Release the Soldering Kraken!
The banana plug pin
All hooked up
The gyro in the gauge didn't start. Damn.
But I had resistance between + and -. And I had voltage! Hmmm..
Second time I hooked it up, I saw a bit of a spark when I put the positive clamp to the battery, and heard something.
I spun the gyro with my finger.... it spun up!
Well, well. So that gyro "froze" in a bit... Yep, it was hard to turn over with a finger - no doubt a small motor in there had a hard time!
I probably "cleared it up" a bit when turning it over with my fingers - but that won't last long... damn.
Are we looking at the overhaul for this thing too now? Sigh.... Maybe I can find parts to do that myself, but not so sure about that.... It's not common for owners to overhaul their instruments - they're precision clockwork, after all...
And I will have to figure out how to solve that wiring problem with no space to hook up the right type connector. I am thinking along the lines of maybe routing a wire from inside of the gauge down thru a hole I'd drill, a grommet it it, and covering the whole business with with some sealant or something, so that the dust doesn't get in. we'll see. Need to ponder this a bit more.
Standard checklist philosophy requires that pilots read to each other the actions they perform every flight, and recite from memory those they need every three years.
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