Can I use this actual aircraft potentiometer?

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jph
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Re: Can I use this actual aircraft potentiometer?

#31 Post by jph »

Well beggar me.
It would certainly seem like the thing is damaged inside. If the 2N3055 power transistor went short then you would potentially get enough power to burn the contacts / contacts connection. Very strange.
It could also be that the other switch is suffering from burnt / sticking contacts hence no click as it cannot move past the detent.
I would take the bloody things apart and fix them. - So get out to the G5 and light the fires ! :D

One thing to consider that you may not have is that the switches / pots combined that you buy would end up with the operation of the click at opposite positions - if you used two to replace what you have. That is due to the Pots being located in opposing directions. So one 'wheel' would have the click at the bottom of the panel and the other at the top of the panel.

Not sure how it works - or should - at the moment in respect of where the clicks are but I would imagine they both operate so the clicks are in the same location meaning they are left and right handed switches - so to speak. That could be a problem. Kirk.
Joe
Joe. CISSP, MSc.

Kaellis991
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Re: Can I use this actual aircraft potentiometer?

#32 Post by Kaellis991 »

Joe,

In the real aircraft only one of the pots has the on/off switch. The NAV/RAD light potentiometer on the left side of the switch panel. The pot for the panel / gauge lights does not have the switch. That potentiometer does not actually turn off the lights to the gauges. It only dims them when necessary .
But you bring up a good point about the location of the switch relative to the turn. The B10k switched pot I have if viewed from the shaft side will rotate counterclockwise to the off position. Since the switched pot has to be on the left side of the panel with the shaft pointing right, the bottom of the turn is where the off will be. So if the pot I have ordered turns and switches the same then all is good.

It might be that Piper designed this switch panel with the NAV/RAD light dimmer on the left side because the switched pots only turn in the counterclockwise direction towards the switch. So with a pot that has a clockwise turn from the off position to increase the brightness, that translates into an up movement of the wheel when the shaft is pointing to the right. And thus why the right hand pot pointing left does not have a switch. If it did, then the switch would be at the top and the brightening of the light would be a down rotation which is counterintuitive for most things in terms of up and down.

Kaellis991
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Re: Can I use this actual aircraft potentiometer?

#33 Post by Kaellis991 »

jph wrote: Sat Jun 25, 2022 3:01 pm Well beggar me.
…….
I would take the bloody things apart and fix them. - So get out to the G5 and light the fires ! :D
………..
Joe
How does one take these “bloody things” apart?
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Kirk

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jph
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Re: Can I use this actual aircraft potentiometer?

#34 Post by jph »

Exactly Kirk,
Yes, the rotation is standard then as it is normal for a shaft potentiometer with switch to be ''off' -(meaning the switch activates) in the fully ANTI-CLOCKWISE direct, which is correct for your panel so that's a relief as you can replace that as you require.

You probably have this one located but if not then the one to order for the 'right' hand side without the switch is going to be the Mouser No. 774-450T328F103A1A1 CTS 450T328F103A1A1

When you get the new one and it fits, if you want I can explain how to take the old one apart and possibly fix it ok. (see next post)

What was confusing on an aircraft - and it did my head in when I started flying for real about 40 years ago - is that in the UK a switch - in a car - or any normal household power, light or appliance switch is ON when it is DOWN - not UP. !!! :o

Very confusing. Of course, the UK MUST be correct and it is the other buggers that are wrong :lol:

In the EU, well certainly in Spain and Portugal, and I believe it was also the same when we lived in France, the switches are normally ON when 'UP' as per 'our colonies'

When we had the house built here I ensured that the switches were wired CORRECTLY ;) - as in 'ON when DOWN.

It is similar to 'Johnny Foreigner' driving on the flipping wrong side of the road. All 'civilised' people drive on the LEFT side of the road. PAH ! HUMBUG !. :D
Joe. CISSP, MSc.

Kaellis991
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Re: Can I use this actual aircraft potentiometer?

#35 Post by Kaellis991 »

Joe,

I didn’t know that about the power switches in the UK. Since I lived in England only until I was 5 years, I guess that is information I just didn’t retain.
The mouser pot will be ordered today.

Kirk

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jph
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Re: Can I use this actual aircraft potentiometer?

#36 Post by jph »

Taking pots apart...
See image here -
kirk switch.jpg
kirk switch.jpg (30.02 KiB) Viewed 906 times
Don't touch the circlip with the green arrow !!

Carefully bend up all the tabs indicates in red. The body drum will then (hopefully) pull GENTLY away from the front plate and shaft assembly leaving the switch mechanism in the rear of the body drum.

The front plate / shaft assembly contains the track or coil and also the wiper (the moving part). In this case the shaft will have an extension on the rear that locates into the switch assembly which is located inside the metal round can housing that lifts off the front plate assembly.

It is probably better to remove the body from the front plate with the switch 'on' so, for example, the pot is in a more or less centre position as there should be no spring load on the switch operating cam on the end of the main shaft.
Joe. CISSP, MSc.

Kaellis991
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Re: Can I use this actual aircraft potentiometer?

#37 Post by Kaellis991 »

Joe,

Actually I was planning on taking apart the non switched pot since it isn’t working, to see if I can even do the dismantling. At least I’ll be able to see how it works or why it doesn’t work even if it cant be fixed.

Kirk

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Re: Can I use this actual aircraft potentiometer?

#38 Post by jph »

No worries.
What I don't quite understand is WHY is there a switch unit on the supposedly 'non-switched' pot ? - it even has wires going to it ! :shock: :?

oh, and when I was 5 the UK had round pin plugs and round switches made of real 'Bakelite' and they were still on when down :lol:
I found out that if I stood on a chair I could unscrew the front of the light switches exposing all the lovely electrons to enquiring little minds and hands .. what a time of joy and exploration and parental bemusement. ;)
Joe. CISSP, MSc.

Kaellis991
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Re: Can I use this actual aircraft potentiometer?

#39 Post by Kaellis991 »

jph wrote: Sat Jun 25, 2022 4:48 pm No worries.
What I don't quite understand is WHY is there a switch unit on the supposedly 'non-switched' pot ? - it even has wires going to it ! :shock: :?

oh, and when I was 5 the UK had round pin plugs and round switches made of real 'Bakelite' and they were still on when down :lol:
I found out that if I stood on a chair I could unscrew the front of the light switches exposing all the lovely electrons to enquiring little minds and hands .. what a time of joy and exploration and parental bemusement. ;)
Maybe the non-switched pot doesn’t work because of the corrosion inside this ancient device. Is there a switch in there?

Sounds like you survived it all intact. My time in England left me with a shorter pinky finger not very conducive for many guitar chords.
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Kaellis991
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Re: Can I use this actual aircraft potentiometer?

#40 Post by Kaellis991 »

So I took the wire I use on my multimeter lead and scraped off some of the corrosion inside where the faulty terminal connects.
I started getting ohm readings between it and the opposite terminal..even on the outer end of the terminal.
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