KX-155 voltage change

weirdjim

weirdjim

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weirdjim
I don't have the book on the 155. Does anybody know, or have done, a mod to change a 28 volt unit to a 14 volt unit?

Thanks,

Jim
 
I don't think you can.

The only thing I noticed remotely related was King had a 10 ohm 55 watt resistor kit that mounted external to the radio allowing a 12 volt KT76A to be installed in a 24 volt airplane.

Lonestar avionics saw a $$ in building a 12 to 24 volt converters more or less specifically for this purpose. There are a lot of late model KX155(A)s out there and overwhelming majority are 24 volt.

 
the manual on page 1-8 show different part #s for different configurations, further into the manual, it appears that the KX-155 is 14V and the KX-165 is the 28 volt unit.

Bob
 
bnt83. it appears you answered the question while I was reading the manual. :)

Bob
 
biplanebob said:
the manual on page 1-8 show different part #s for different configurations, further into the manual, it appears that the KX-155 is 14V and the KX-165 is the 28 volt unit.

Bob
Click to expand...

I don't think that's true.

The 155 and 165 were both available in 12 and 24 volt. The difference is the 165 has the VOR/LOC Converter inside the unit and therefore does not work with the CDIs that contain the VOR/LOC converter.




http://www.bennettavionics.com/ki206.html
 
bnt83 said:
As far as I know all KX155A/165A are 24 volt tho.
Click to expand...
Actually, AFaIK the KX155A/165A navcoms will work on both voltages without any changes to the radio or tray connections.

The "non A" KX155/165 radios come in two different configurations, one for 14V and one for 28V and there's no (legal) way to convert from one to the other. The wiring difference on the tray is designed so that plugging the wrong voltage model in won't power or harm the radio. A 14V radio takes power on pins 14 and R and the wiring for a 28V tray connects two optional remote switches to those pins. Similarly the 28V radio takes power on pins 13 and P with the remote switch inputs on 14 and R.
 
kgruber said:
They are 28V.
Click to expand...
Interesting. I checked the install manual and like you said, it says 28VDC for the power input. But the maintenance manual clearly says that there's a switching power supply which will work with 11-30VDC and the lighting input can be wired for 14 or 28v. I wonder if they designed it for both voltages and then decided to limit installations to 28V only for some reason.
 
kgruber said:
Yes, the system is 28V. That is what the alternator supplies to the electronics/motors. Only the battery is 24V.
Click to expand...

The terms are interchangeable. We all know that 12/14 volt systems include 14/12 volt systems and the same for 28/24, 24/28. And the alternator does NOT supply 28 volts to the battery bus (that's the correct technical term for it). That voltage is dependent on temperature, voltage regulator setting, and a few other minor players. The most COMMON 24 volt bus is somewhere around 26.8 volts. However, we all design our electronics to operate down to 23 and up to 29 (or 11.5 to 14.5) continuous with spike protection above that.

Of course, since you've obviously been designing electronics for aircraft for the last 50 years you knew that, didn't you?

Jim
 
gismo said:
Actually, AFaIK the KX155A/165A navcoms will work on both voltages without any changes to the radio or tray connections.

there's no (legal) way to convert from one to the other.
Click to expand...

The word "legal" never entered into the question.

To paraphrase Teddy Roosevelt's attorney general, when Teddy asked him if it was legal to build the Panama Canal, "Oh, Mr. President, do not let legalities stand in the way of such a great and noble undertaking."

Jim
 
weirdjim said:
The terms are interchangeable. We all know that 12/14 volt systems include 14/12 volt systems and the same for 28/24, 24/28. And the alternator does NOT supply 28 volts to the battery bus (that's the correct technical term for it). That voltage is dependent on temperature, voltage regulator setting, and a few other minor players. The most COMMON 24 volt bus is somewhere around 26.8 volts. However, we all design our electronics to operate down to 23 and up to 29 (or 11.5 to 14.5) continuous with spike protection above that.

Of course, since you've obviously been designing electronics for aircraft for the last 50 years you knew that, didn't you?

Jim
Click to expand...


Yes, I've been seeing your drivel for decades.

And while you were stroking your ego, I was actually out there flying the world.
 
biplanebob said:
the manual on page 1-8 show different part #s for different configurations, further into the manual, it appears that the KX-155 is 14V and the KX-165 is the 28 volt unit.

Bob
Click to expand...
The KX-155 and KX-165 are different radios (far more than voltage difference). The KX-165 uses a different indicator (drives an HSI-style resolver) and has additional featuers not present in the 155.

However I believe the other poster is correct. You can't make a 14 V into a 28V unit (or 12 or 24 if you wish). It's not just a jumper/tray change.
 
Here is a more important question concerning the 155A. The current model is 25khz freq. spacing. In the near future we will have to transition to 8.33khz spacing. The 155A/165A which are sold in Europe have 8.33 spacing. How can the spacing be changed on the 25khz radios. I know it can be done but my install manual does not explain.
 
Walt said:
Here is a more important question concerning the 155A. The current model is 25khz freq. spacing. In the near future we will have to transition to 8.33khz spacing. The 155A/165A which are sold in Europe have 8.33 spacing. How can the spacing be changed on the 25khz radios. I know it can be done but my install manual does not explain.
Click to expand...

I'm not sure that is going to happen in our lifetime. What is your basis for this information on the switch to 8.33? The only reason Europe has decided they need 3x the number of channels (which makes IF filtering a *****, btw) is the density of the population and distance between population centers.

Jim
 
flyingron said:
The KX-155 and KX-165 are different radios (far more than voltage difference). The KX-165 uses a different indicator (drives an HSI-style resolver) and has additional featuers not present in the 155.

However I believe the other poster is correct. You can't make a 14 V into a 28V unit (or 12 or 24 if you wish). It's not just a jumper/tray change.
Click to expand...

But can you go the other way? 28 to 14? There are a lot of junker 28 volters out there that I'd like to experiment on to make a really cheap drop-in LED display.

Jim
 
Jim,
The change to 8.33 will occur when the NextGen folks want to turn on the text messaging system. The freqs for the system are interspersed in the VHF sprectum.
Years ago the FAA asked for more sprectum from the FCC and the FCC said no. Only way to accommodate text messaging was to go to 8.33. When implemented the big airplanes will speak directly with the air traffic computer. The whole point to to cut down on radio traffic and to cut down on the number of controllers. Way down the road the controllers will become monitors of the decisions the computer is making.
 
Walt said:
...Way down the road the controllers will become monitors of the decisions the computer is making.
Click to expand...

"Self driving" control towers. :eek:

Run by Apple, Elon, Google or Uber? ;)
 
Walt said:
Jim,
The change to 8.33 will occur when the NextGen folks want to turn on the text messaging system. The freqs for the system are interspersed in the VHF sprectum.
Years ago the FAA asked for more sprectum from the FCC and the FCC said no. Only way to accommodate text messaging was to go to 8.33. When implemented the big airplanes will speak directly with the air traffic computer. The whole point to to cut down on radio traffic and to cut down on the number of controllers. Way down the road the controllers will become monitors of the decisions the computer is making.
Click to expand...

I don't mean to challenge your understanding, but 8.33 spacing simply splits the 25 kHz. channels into thirds. I asked for some sort of "feeler" that the FAA is considering using this split.

The FCC responded, by the way, from reassigning 136-137 (40 more 25 kHz channels) from Space Operations to Aviation.

The NextGenNextGen will get rid of the AM double sideband modulation scheme to something reasonable and not out of the 1920s.

Jim
 
weirdjim said:
The NextGenNextGen will get rid of the AM double sideband modulation scheme to something reasonable and not out of the 1920s.
Click to expand...
By the time that comes around, we'll be out of the analog voice mode of issuing ATC instructions and into something completely digital.
 
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