Name That Knob hanging under the panel

Pedals2Paddles

Pedals2Paddles

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Pedals2Paddles
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This is hanging down under the panel of a C150G. Any guesses? I have a feeling whoever did avionics work on this thing in the past was a moron.
 
Best guess is an old-fashioned multiwatt lamp dimmer control. Nice wiring ratsnest you've got there :yes:

Jim
 
In order to work on type certificated aircraft, you have to have the proper credentials to sign off the work and return the aircraft to service so this can't be a picture of a Cessna 150. :rolleyes:

It's most likely a dimmer for the light on something - perhaps a radio or transponder? Not the whole panel or anything that draws a lot of current.

Volume control for something would be the distant second guess.
 
Obviously the volume knob from a fender strat.
 
I was thinking it is part of the tachyon emitter system.

The dome and panel lights have knobs on the ceiling, so not for that. Possibly the speaker in the ceiling, I'll try that later.

Part of me wants to take that whole mess apart and fix it. And part of me wants to quietly tuck it under the panel and pretend I never saw it.
 
What happens when you turn it? Panel lights change, coms get louder or more static, flaps move up and down, wheels lose air pressure? :dunno:
 
Well I haven't tried turning it with the big red switch turned on yet. I was busy with some other things and figured maybe I'd ask first. However I have a feeling everyone here's guess will be as good as mine with this silly thing.

What seems exceptionally stupid is that the only actual connected wires are on the outer two pins. On most potentiometers, those two cancel eachother out. You would always wire it in with an outside and center pin. So theoretically, the way it is wired, it actually does nothing at all.
 
Pedals2Paddles said:
Well I haven't tried turning it with the big red switch turned on yet. I was busy with some other things and figured maybe I'd ask first. However I have a feeling everyone here's guess will be as good as mine with this silly thing.

What seems exceptionally stupid is that the only actual connected wires are on the outer two pins. On most potentiometers, those two cancel eachother out. You would always wire it in with an outside and center pin. So theoretically, the way it is wired, it actually does nothing at all.
Click to expand...

There is equipment out there with dimer circuits that work opposite of the norm. The Electronics International engine gauges I have use voltage to dim the LEDs. The higher the voltage on the circuit the darker they get.

But what I can see in the picture makes no sense to me.
 
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Turn the lights on, listen to the radio, turn the knob, see what is affected.:D
 
Pedals2Paddles said:
Well I haven't tried turning it with the big red switch turned on yet. I was busy with some other things and figured maybe I'd ask first. However I have a feeling everyone here's guess will be as good as mine with this silly thing.

What seems exceptionally stupid is that the only actual connected wires are on the outer two pins. On most potentiometers, those two cancel eachother out. You would always wire it in with an outside and center pin. So theoretically, the way it is wired, it actually does nothing at all.
Click to expand...

Actually, the way it's wired it is a fixed resistor. Probably 150K ohm as that is a very common value. Why that was needed there and why somebody had a pot and didn't have a regular resistor I have no idea. But if you are correct on what's wired, you are correct in that turning the shaft will make no difference.

John
 
jsstevens said:
Actually, the way it's wired it is a fixed resistor. Probably 150K ohm as that is a very common value. Why that was needed there and why somebody had a pot and didn't have a regular resistor I have no idea. But if you are correct on what's wired, you are correct in that turning the shaft will make no difference.

John
Click to expand...

I will bet anything that this plane was owned by a HAM at some point. :rofl: :idea:Here's a guess, that resistor is needed in the microphone circuit to deal with modern mics. He knew a 150k Ohm resistor would work and that was the one he found in his pocket with his change, so that's the one that went in.:dunno::rofl:
 
Henning said:
I will bet anything that this plane was owned by a HAM at some point. :rofl: :idea:Here's a guess, that resistor is needed in the microphone circuit to deal with modern mics. He knew he needed a 150k Ohm resistor and that was the one he found in his pocket with his change, so that's the one that went in.:dunno::rofl:
Click to expand...

Sounds about right. And it's probably worked just fine for years...
 
As a ham myself, I resemble that remark. :D

Except I'm < 100 yrs old :lol:
 
Capt. Geoffrey Thorpe said:
It's most likely a dimmer for the light on something - perhaps a radio or transponder? Not the whole panel or anything that draws a lot of current.

Volume control for something would be the distant second guess.
Click to expand...


I dunno, that looks awfully like a 10 watt wirewound pot. That SHOULD take a whole lot of panel lights. Wouldn't probably use this hefty of a pot on volume unless I was controlling speakers on a rock band.

Jim
 
Pedals2Paddles said:
What seems exceptionally stupid is that the only actual connected wires are on the outer two pins. On most potentiometers, those two cancel eachother out. You would always wire it in with an outside and center pin. So theoretically, the way it is wired, it actually does nothing at all.
Click to expand...

That wasn't evident in the photo. IF that is true (center pin not connected) then it is an emergency control. You diddle around with it while you figure out what to do with the emergency.

Jim
 
jsstevens said:
Probably 150K ohm as that is a very common value.
Click to expand...


If that is a 10 watt wirewound as I suspect that it is, getting much above 5 or 10k ohms is going to be difficult as that is a LOT of hairfine wire, even nichrome, and large resistor values and high wattage don't go hand in hand.

And I resemble the ham comment. We can be as clean and neat or as slobby and haywire as the next guy. I'll show you a sanitary 2 meter installation next time I take pictures of the airplane and I defy you to find the antenna installation.

Jim
 
weirdjim said:
If that is a 10 watt wirewound as I suspect that it is, getting much above 5 or 10k ohms is going to be difficult as that is a LOT of hairfine wire, even nichrome, and large resistor values and high wattage don't go hand in hand.

And I resemble the ham comment. We can be as clean and neat or as slobby and haywire as the next guy. I'll show you a sanitary 2 meter installation next time I take pictures of the airplane and I defy you to find the antenna installation.

Jim
Click to expand...

I'm not saying that it's impossible to beat genetics, after all, Gingers exist, but a Pilot and a HAM has two genetic strikes on the 'Cheap' board. If he has a sailboat too, he is genetically destined to do things as pictured.:rofl:
 
Oh I used to have a boat too. It was in a similar state of disarray when I purchased it. And remained that way. My only regret with that boat was never forgetting to put the drain plug back in before launching in deep water......
 
Henning said:
I'm not saying that it's impossible to beat genetics, after all, Gingers exist, but a Pilot and a HAM has two genetic strikes on the 'Cheap' board. If he has a sailboat too, he is genetically destined to do things as pictured.:rofl:
Click to expand...

That would be


  • 1750867CFI A&G, IA
  • WX6RST Extra
  • Sail #422 Catalina 22
Thanks,


Jim
 
weirdjim said:
I dunno, that looks awfully like a 10 watt wirewound pot. That SHOULD take a whole lot of panel lights. Wouldn't probably use this hefty of a pot on volume unless I was controlling speakers on a rock band.

Jim
Click to expand...

Hmm, does it go to 11?
 
I think whatever it did do it probably stopped doing it around 1978 or thereabouts...
 
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