Can I use this actual aircraft potentiometer?

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jph
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Re: Can I use this actual aircraft potentiometer?

#21 Post by jph »

Well they wouldn't be made in the US as you need quality and reliability.. :lol:
The good old 2N3055 power transistor. We used to use a bank of 6 of them in 13.8V power supplies. Old but good and still made today.
So, the pots are actually driving the base of the 3055 as a linear shunt regulator for the dimmers. Ok. sO now we know WHAT it does and how it does it, it means you possibly have a shorted transistor that's cocking up the switch reading.
They can go - well, you don't need to remove them, but the wiring DEFINITELY around the power transistors definitely has to go for the sim conversion.
snip the wires and try again.
Joe. CISSP, MSc.

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jph
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Re: Can I use this actual aircraft potentiometer?

#22 Post by jph »

Actually the first transistor is a Yank one - Motorola - Made in Mexico in July 1990. Long before the company imploded and lost billions then sold off all it's assets.
Joe. CISSP, MSc.

Kaellis991
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Joined: Mon Sep 07, 2020 8:49 am

Re: Can I use this actual aircraft potentiometer?

#23 Post by Kaellis991 »

jph wrote: Sat Jun 25, 2022 12:27 pm Actually the first transistor is a Yank one - Motorola - Made in Mexico in July 1990. Long before the company imploded and lost billions then sold off all it's assets.
Must be a maquiladoras product.

Kaellis991
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Re: Can I use this actual aircraft potentiometer?

#24 Post by Kaellis991 »

jph wrote: Sat Jun 25, 2022 12:15 pm Well they wouldn't be made in the US as you need quality and reliability.. :lol:
The good old 2N3055 power transistor. We used to use a bank of 6 of them in 13.8V power supplies. Old but good and still made today.
So, the pots are actually driving the base of the 3055 as a linear shunt regulator for the dimmers. Ok. sO now we know WHAT it does and how it does it, it means you possibly have a shorted transistor that's cocking up the switch reading.
They can go - well, you don't need to remove them, but the wiring DEFINITELY around the power transistors definitely has to go for the sim conversion.
snip the wires and try again.
I’ll get my axe…

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jph
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Joined: Fri Apr 10, 2020 12:50 pm
Location: Somewhere over the rainbow..

Re: Can I use this actual aircraft potentiometer?

#25 Post by jph »

Kaellis991 wrote: Sat Jun 25, 2022 12:34 pm

I’ll get my axe…
:lol:

And the venerable 2N3055 power transistors were gently laid to rest - with a very large Axe :D I like it.
Joe. CISSP, MSc.

Kaellis991
Posts: 581
Joined: Mon Sep 07, 2020 8:49 am

Re: Can I use this actual aircraft potentiometer?

#26 Post by Kaellis991 »

jph wrote: Sat Jun 25, 2022 12:40 pm
Kaellis991 wrote: Sat Jun 25, 2022 12:34 pm

I’ll get my axe…
:lol:

And the venerable 2N3055 power transistors were gently laid to rest - with a very large Axe :D I like it.
That changed nothing. Still the same terminals are connecting regardless of switch position.
I’ve got an SPST pot, with D shaft, 10k, 320 degrees, and correct shaft diameter ordered. It’s the closest I could find.
CTS 450T328F103A1C1.
If I can’t get the switch on the functioning pot to work, I could swap it out for the inoperative one and use that new switched pot in it’s place.

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jph
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Re: Can I use this actual aircraft potentiometer?

#27 Post by jph »

Interesting - send me a piccy of the switches now with whatever wiring is left please.
Joe. CISSP, MSc.

Kaellis991
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Joined: Mon Sep 07, 2020 8:49 am

Re: Can I use this actual aircraft potentiometer?

#28 Post by Kaellis991 »

jph wrote: Sat Jun 25, 2022 1:15 pm Interesting - send me a piccy of the switches now with whatever wiring is left please.
This is the switched pot. All wires are disconnected from the transistors. Also I cut the common wires from the molex over to the opposite side non-functioning pot.
Still cant figure out how to remove the molex connector cleanly....

Wouldnt the 4 terminals on the end of the pot mean that it is a DPST switch?
IMG_0636-2.jpg
IMG_0637 (002).jpg

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jph
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Re: Can I use this actual aircraft potentiometer?

#29 Post by jph »

Hi,
Yes, normally that would indicate a double pole single throw (DPST)
It is so frustrating being several thousand miles away as I would just like to stick it on the bench here. :?
Just for sanity's sake are you absolutely 100% certain that -

A: all 4 terminals on the seemingly working (clicking) switch are definitely disconnected from each other ? - better still to disconnect the terminals completely - remove the wires - and
B: There is simply no combination of metering across any combination of terminals that makes any change with the switch in one position or the other ?
:shock:
Joe. CISSP, MSc.

Kaellis991
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Re: Can I use this actual aircraft potentiometer?

#30 Post by Kaellis991 »

jph wrote: Sat Jun 25, 2022 2:11 pm Hi,
Yes, normally that would indicate a double pole single throw (DPST)
It is so frustrating being several thousand miles away as I would just like to stick it on the bench here. :?
Just for sanity's sake are you absolutely 100% certain that -

A: all 4 terminals on the seemingly working (clicking) switch are definitely disconnected from each other ? - better still to disconnect the terminals completely - remove the wires - and
B: There is simply no combination of metering across any combination of terminals that makes any change with the switch in one position or the other ?
:shock:
Out of the four terminals, two sets are connected. And the connection doesn’t change with the switch position.
I removed the 4 wires at the switch poles and checked the terminals again with my continuity testing multimeter.
Still the same. If switch is on or off the two terminals on either side of the little red wires I placed as reference, are connected continuously. No other combo of terminals gives me the beep on the multimeter.

It is possible that the switch, even though it clicks, doesn’t work. It’s not a huge issue for me if I have to replace the pots. My main concern was getting the wheels and the proper switch plate. I went into this assuming I’d have to replace the pots.

Perhaps I’ll just take a quick hop to Portugal in my Gulfstream….. :lol:
B17ACB27-CF12-4EA5-B9CF-4F9A3E60194A.jpeg

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