Need some pot

[Guitarmaster]

Ok, well... Need a pot. Potentiometer that is.

Does anyone know the specs of the instrument lighting pot? The parts catalog and Google are suspiciously silent on the subject.

I know rewiring a PWM would be the way to go, but the pot is easy and I already had the transistor panel out once... Not a job I want to do again.

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https://goo.gl/photos/5qcquVcBGh1PyiKx5

[Yetti]

Those pictures look like the diode bridge that sits on top of the wheel well

[Yetti]

http://www.digchip.com/datasheets/parts/datasheet/3883/2N3079-pdf.php

 

just need to find a cross reference match

[Yetti]

Like the molex plugs for the bendix king radios may be out of luck

Should be able to find an upgraded plate that would do the same thing.  What does this do?  Or like you said PWM for $15 is your friend.

Searched via the case type T0-36

http://www.interfacebus.com/semiconductor-transistor-case-outlines-obsolete-jedec-types.html

 

[N201MKTurbo]

Do you need a pot or transistors? what is wrong? Have you checked the fuses?

[Guitarmaster]

Like the molex plugs for the bendix king radios may be out of luck

Should be able to find an upgraded plate that would do the same thing.  What does this do?  Or like you said PWM for $15 is your friend.

Searched via the case type T0-36

http://www.interfacebus.com/semiconductor-transistor-case-outlines-obsolete-jedec-types.html

 

The pot acts as the base resistor for the transistor. I pulled the transistors and they tested fine, but I replaced them with new ones anyway since I had them out.

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[Guitarmaster]

Do you need a pot or transistors? what is wrong? Have you checked the fuses?

I replaced the transistors.

When operating at 12v, the lights will stay on and work fine. When 14v is coursing through the system, the lights work for a short time, begin to flicker then blow the 5A fuse.

When i installed the PWM for the bezel lights, I was tired and shorted the circuit. The power for the PWM was being drawn from the hot side of the rheostat. When it shorted, it blew the fuse and the breaker.

At that time, I thought I had damaged the transistor, but it tested ok. I replaced anyway since I had one.

Upon further circuit analysis, I think the rheostat is damaged and internally shorts causing spikes in the light circuit thereby blowing the fuse.

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[DrBill]

Here's the circuit I got from  one member.

Measure one of them end to end.Then get it from Digikey or Mouser. If you need help computing the power, let me know.

Bill

 

[DrBill]

lets see, its a 5A fuse, so with a power transistor and Beta  of 10  means base current = 0.5A at full on.

need 0.7 v on base at 0.5A so need to drop 12.9v at 0.5 a = 6.5 watts so a 10 watt pot would do.

low end resistance = 12.9 / 0.5 = 25.8 ohms.  High end should be about 10x that for full control or 250-300 ohms.

I'd look for a 300 ohm , 10 watt pot in the size you need.

I think that may be a challenge, 10 watts is pretty high for a pot like that.

will not fit in package, have to see what is there.. must be 5 w or less.

Bill

here's a 5w 500 ohm pot

for 5.34

http://www.digikey.com/product-detail/en/cts-electrocomponents/026TB32R501B1A1/CT2156-ND/203777

[Guitarmaster]

lets see, its a 5A fuse, so with a power transistor and Beta  of 10  means base current = 0.5A at full on.

need 0.7 v on base at 0.5A so need to drop 12.9v at 0.5 a = 6.5 watts so a 10 watt pot would do.

low end resistance = 12.9 / 0.5 = 25.8 ohms.  High end should be about 10x that for full control or 250-300 ohms.

I'd look for a 300 ohm , 10 watt pot in the size you need.

I think that may be a challenge, 10 watts is pretty high for a pot like that.

will not fit in package, have to see what is there.. must be 5 w or less.

Bill

here's a 5w 500 ohm pot

for 5.34

http://www.digikey.com/product-detail/en/cts-electrocomponents/026TB32R501B1A1/CT2156-ND/203777

Awesome! Thanks!

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[DrBill]

if when you open it, measure the pot and R3 and R4 (if you have the two channel version) and I'll update the drawing for next time.

Bill

 

[Guitarmaster]

I have had it with transistors and 50-year-old technology!  In with the PWM's!  The hanger elves removed the transistor panel altogether and rewired the system to work with PWM.  Plugged it all in and.......  NO MAGIC SMOKE!  YES!  

It was actually a fairly easy job.  All of the re-routing of connections was done on the transistor side of the cannon plug.  Inline 5A fuses replaced the very expensive, hard-to-find and vulnerable GMW 5 fuses.

Nice to have the instrument lights back.  It's a big help at night.  

Side note:  I have three, two of which are new, 2N2016 transistors for sale.

Cheers!

 

[Guitarmaster]

On July 12, 2016 at 11:39 AM, daver328 said:

Nice title.

I thought, "This guy must live in Colorado or Washington?"

Those new medical requirements for PPL sure are going to make this interesting!"

I DID used to live in WA.   In fact, I spent two years trying to kill myself in the weather, over the mountains in a Seneca2 and Chieftain every night.   Ahhh, the days of building time.  

[Yetti]

My F has what is basically a J panel with a pretty extensive circuit breaker panel.... It bothers me that there are still inline fuses behind the panel.  One day I may have to fix that.

[Guitarmaster]

Just now, Yetti said:

My F has what is basically a J panel with a pretty extensive circuit breaker panel.... It bothers me that there are still inline fuses behind the panel.  One day I may have to fix that.

Mine is the same.  I, as well, have always found it interesting that there are still inline fuses.  I suspect they are carryovers from earlier models.  The inst light breakers are 10A and the inline fuse is 5A.  The only thing I can come up with is they were there to protect the transistors from current spikes and the breaker is only there to handle a dead short condition.  Now they protect the PWM from damage.

[Yetti]

Yea I have 2 -10 amp breakers for 3 pots. Some day need to trace it all out.  Not sure a fuse is used for voltage spikes, the battery is supposed to take care of any spikes.  That and the breaker on the field for the alternator.

[Marauder]

My F has what is basically a J panel with a pretty extensive circuit breaker panel.... It bothers me that there are still inline fuses behind the panel.  One day I may have to fix that.

Just now, Yetti said: My F has what is basically a J panel with a pretty extensive circuit breaker panel.... It bothers me that there are still inline fuses behind the panel.  One day I may have to fix that.

Mine is the same.  I, as well, have always found it interesting that there are still inline fuses.  I suspect they are carryovers from earlier models.  The inst light breakers are 10A and the inline fuse is 5A.  The only thing I can come up with is they were there to protect the transistors from current spikes and the breaker is only there to handle a dead short condition.  Now they protect the PWM from damage.

That was my 2013 project:

Before:

After:

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[ArtVandelay]

My F has what is basically a J panel with a pretty extensive circuit breaker panel.... It bothers me that there are still inline fuses behind the panel.  One day I may have to fix that.

Just now, Yetti said: My F has what is basically a J panel with a pretty extensive circuit breaker panel.... It bothers me that there are still inline fuses behind the panel.  One day I may have to fix that.

Mine is the same.  I, as well, have always found it interesting that there are still inline fuses.  I suspect they are carryovers from earlier models.  The inst light breakers are 10A and the inline fuse is 5A.  The only thing I can come up with is they were there to protect the transistors from current spikes and the breaker is only there to handle a dead short condition.  Now they protect the PWM from damage.

That was my 2013 project:

Before:

After:

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Since you added a JPI afterwards, what did you do with your FF gauge?

[Marauder]

My F has what is basically a J panel with a pretty extensive circuit breaker panel.... It bothers me that there are still inline fuses behind the panel.  One day I may have to fix that.

Just now, Yetti said: My F has what is basically a J panel with a pretty extensive circuit breaker panel.... It bothers me that there are still inline fuses behind the panel.  One day I may have to fix that.

Mine is the same.  I, as well, have always found it interesting that there are still inline fuses.  I suspect they are carryovers from earlier models.  The inst light breakers are 10A and the inline fuse is 5A.  The only thing I can come up with is they were there to protect the transistors from current spikes and the breaker is only there to handle a dead short condition.  Now they protect the PWM from damage.

That was my 2013 project:Before:

After:

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Since you added a JPI afterwards, what did you do with your FF gauge?

Kept both.

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[Yetti]

What I don't get is 10 amps * 2 for instrument lights. is a lot of amps. 

What is an "ACU"?  In a 170B the Com and Nav are actually separate sides of the radio which makes for good comm and nav circuit breakers segregation.  In the KX155 the wiring could be separate but it is shown tied together at the radio.  So why does do you still have the "Nav" circuit breakers?  Should one not say GPS 1 and GPS 2 with all your fancy pants glass?

[Marauder]

What I don't get is 10 amps * 2 for instrument lights. is a lot of amps. 

What is an "ACU"?  In a 170B the Com and Nav are actually separate sides of the radio which makes for good comm and nav circuit breakers segregation.  In the KX155 the wiring could be separate but it is shown tied together at the radio.  So why does do you still have the "Nav" circuit breakers?  Should one not say GPS 1 and GPS 2 with all your fancy pants glass?

I believe the two breakers were to cover the instrument brow & radio lights and the second breaker covered the annunciator and the overhead light.

The ACU is the digital to analog controller for the Aspens. The reason there are two Nav are for the two Nav sides of the radios (GTN 650 and the GNC 255B).

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[Yetti]

A couple questions.   Did you drill the rivets to remove the panel to get at the wiring?   I am guessing co pilot side?   Did you combine all three dimmers onto one PWM.   What size PWM? 15 Amps seems like it would do it for all. 

[air cooled dad]

On July 20, 2016 at 9:56 PM, Guitarmaster said:

I DID used to live in WA.   In fact, I spent two years trying to kill myself in the weather, over the mountains in a Seneca2 and Chieftain every night.   Ahhh, the days of building time.  

Did you fly for Airpac???

[Guitarmaster]

39 minutes ago, Yetti said:

A couple questions.   Did you drill the rivets to remove the panel to get at the wiring?   I am guessing co pilot side?   Did you combine all three dimmers onto one PWM.   What size PWM? 15 Amps seems like it would do it for all. 

I didn't take the wheel well covers off.  It was a major PITA to get the transistor panel out, but i was determined I was not taking that wheel well cover off again.  If you have the quadrant, it is somewhat easier because you can see most of the screws.

This is the PWM I used:  https://amzn.com/B001CM74R2

I used two of them.  One for the instrument lights and one for the radio lights.  I didn't have a third pot... although it was on the schematic.  
They are 7A each and have built in protection.  Something to note, with the transistors, there was considerable heat buildup.  There is no or very little heat with the PWMs.  They operate at ~100hz and there is no interference with the radios.
Doing this mod requires you re-wire the transistor panel wiring coming from the cannon plug. If you were really ambitions, you could remove the cannon plug all together, but it was easier to to leave it. I was able to use all existing wiring, I just had to "repurpose" them.  I made notes on what to do.  I would be happy to send them to you, but yours may be different.
Upon measuring the current draw, the instrument lights pull 3.5A and the radio lights 1.5A.  With the PWM, I can now replace the power-hog, heat-monger incandescent lights with LED.  

 

[Guitarmaster]

13 minutes ago, air cooled dad said:

Did you fly for Airpac???

Yes I did...