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ExpBus 2 Problem.

C

Chalkie

Member
Hope someone can advise me. I live in South Africa and this is the third aircraft I have built and fitted the ExpBus 2. My previous build (about 8 years ago) was an RV-9A for my daughter.

This aircraft had an odd problem, with Master Switch on the Avionic buss was live. All pins had about 5v on them. Emails back and forth with the company and eventually the unit was returned. (Not an easy project this far away.)

Long story... there was nothing wrong with the unit. :confused:

The company asked "did you earth pin XXX" (I can't remember which pin.) My answer was NO. It does not say so in the installation manual.

Does anyone know which pin the company might have referred to? I did not keep the old manual, nor the email.

Pin J16 and PinP10/J10 are earthed for the Exp and firewall mounted solenoid in my new RV-9.

If I switch on the Master Switch (AV Master and G3x are off) Garmin GNC255 (Nav/Comm) is powered up. (Avionics from Stein Air who supplied wiring diagram)

With Master Sw off and G3x booted up with power from backup battery through the backup feature of the Exp Bus 2, the GNC 255 is power up.

Real strange...:confused:

The only thing different in my ExpBus was I had to make my own jumper when removing the square 35Amp master solenoid. My unit did not have the jumper and Aircraft Spruce did not respond to my email of complaint.

I will have to find a solenoid to give PIN numbers I 'jumped' They were the main power supply in-out pins.
 
Interesting. I was just discussing a problem a friend has with EXP Bus here at SnF. His is with the onboard relay.

Since I interacted with ControlVision when the first produced this, I have documentation at home airport. Send me email at jclarkmail AT gmail DOT com and will look it up.

I have been successfully running my EXPBus system for about 20 years now.
 
kiwipete said:
Chalkie

The installation manual

https://www.aircraftspruce.com/catalog/pdf/11-00430tech.pdf

Hope this helps.

In the past I found mine played up when it got damp when the aircraft was left outside. I found using a small dehumidifier solved the problem and it never reccourred.

Regards

Peter
Click to expand...

Thanks, Peter. I do have the manual, I am just trying to understand why the avionic bus is powered with Avionic Master OFF.

Tomorrow I will crawl under the panel. My favourite fun thing to do.:rolleyes:
 
A friend uses the exp bus so I have played with it a few times. I know he can power the avionics (think switch is called cl delivery) with the master switch off, to use the radio, call clearance delivery.
 
climberrn said:
A friend uses the exp bus so I have played with it a few times. I know he can power the avionics (think switch is called cl delivery) with the master switch off, to use the radio, call clearance delivery.
Click to expand...

Hi Joel, I am aware of that function, (clearance delivery) but have not used it.
 
Exp Bus 2 Problem - Solved.

Chalkie said:
Hi Joel, I am aware of that function, (clearance delivery) but have not used it.
Click to expand...

:rolleyes: You were right, I took power from AUX 2 for Comm 1 and audio panel. Aux 1 supplies the G3x.

Wiring was done over a year ago, I forgot, so the problem has been solved. The reason I chose Aux 2 for Comm 1 is because it has an 11 amp fuse. The largest fuse on the Avionic Buss is 7 amps which is not enough for the GNC 255.

On the subject of this thread, the pin Control Vision referred to years ago, is pin 5; that grounds the circuit board. 10 or 15 years ago, that gem of information was not in the installation manual I received.

In mitigation: Previously I had used the Clearance Delivery function to power Comm 1. The problem was, the audio panel was not powered, so to make Comm 1 work, I had to switch off the audio panel to force it into 'fail mode.' This was a pain, so I stopped using it.

On this installation Aux 2 supplies both Comm 1 and the audio panel, so CL DEL should work. :)
 
kiwipete said:
Chalkie

Good to hear you got it sorted and thanks for posting the solution.

Regards

Peter
Click to expand...

The solution was quite simple. The avionics master switch supplied with the Exp Bus is a DPST switch so all I have to do is wire Aux 2 power through the unused poles and all is solved.
 
Chalkie said:
The solution was quite simple. The avionics master switch supplied with the Exp Bus is a DPST switch so all I have to do is wire Aux 2 power through the unused poles and all is solved.
Click to expand...

Yeah. Right. :mad:

Boy did I have fun under the panel, chasing down proverbial rabbit holes. Unfortunately my simple 'Quick Fix' caused a lot of problems, false leads and frustration...

In aviation if you do something and things start to go pear shaped; undo what you did. So I did that.

Long story - short... The Avionics Master switch supplied with the ExpBus 2 looks like a DPST switch (which it is) but it is compromised by a 110v incandescent globe buried in the switch. I could not understand why I was getting a reading of 56 Ohms across the centre terminals, so I decided to open the switch and look.

/Users/chalkiestobbart/Desktop/20220414_130700.jpeg

This globe shorted out the Avionic Bus when I connected Aux power supply for Comm 1 to the second pole of the switch. I had one unused (AB 4) terminal which I wired to my voltage reader. It read 0.3v with Avionic master on. That is a sign of a short as the electronic fuse needs to 'leak' a bit of electricity to keep it hot to close the circuit.

Finally my Avionic Bus is working as intended except for a transponder setup issue. The Remote Garmin Transponder is ADSB IN/OUT and I need to do the setup so that it talks to all others on the G3x system.
 
Now I need to learn how to post a picture...

/Users/chalkiestobbart/Desktop/20220414_130700.jpeg
 

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