VPX Issues That No One Can Solve

[stigaro]

My suggestions:

1. Check all your wiring to ensure that there are no sharp bends or pinches anywhere. A pinch or shard bend could easily be affecting more than one wire.
2. Do you have the circuit breaker values on the VPX set to appropriate levels?
3. How many devices do you have connected to each VPX output? Ideally just one device per output.
4. On the ground, replace the power source feeding the VPX with an adjustable power supply. Then start changing the supply voltage from 13V down to less than 10V and see if the behavior is similar to what you see while flying. You supply voltage could be fluctuating or you battery is going bad.

There are hundreds of VPX devices flying every day. They are quite robust and your experience does not appear to correlate with other peoples experiences with these devices. Your failure mode is not consistent with the way the VPX works so it would seem the problem is likely outside the VPX.

 

[georgemohr]

My suggestions:

1. Check all your wiring to ensure that there are no sharp bends or pinches anywhere. A pinch or shard bend could easily be affecting more than one wire.
2. Do you have the circuit breaker values on the VPX set to appropriate levels?
3. How many devices do you have connected to each VPX output? Ideally just one device per output.
4. On the ground, replace the power source feeding the VPX with an adjustable power supply. Then start changing the supply voltage from 13V down to less than 10V and see if the behavior is similar to what you see while flying. You supply voltage could be fluctuating or you battery is going bad.

There are hundreds of VPX devices flying every day. They are quite robust and your experience does not appear to correlate with other peoples experiences with these devices. Your failure mode is not consistent with the way the VPX works so it would seem the problem is likely outside the VPX.

My thoughts on the above

1) Yep (but it does sound like the OP traced all the wires)
2) If that was true, the VPX would report FAULT on the G3X and the device would stay off (not cycle)
3) Yep
4) Yep nice idea

 

[TroyBranch]

Troy I'm assuming that all your devices are connected to the same "Avionics Master" switch behavior in the VPX right? So if the toggle switch was faulty it would probably cycle all the devices at once, yes?

Yes it is all on the same switch but it is not shutting down everything. The first time was intermittent audio then the 355 starting cycling on and off. Changed the vpx and audio has been good but not the 355. Wired 355 nav direct power. It’s fixed it but now 750 is having the same issue as the 355 did. I am not sure if the audio panel went out yesterday. It sounded like it did but I was to busy trying to trouble shoot the radios.

 

[georgemohr]

K, something else to try. Move all the devices to a different switch (like say swap your AviMaster with your Strobe switch) and fly for a while.

 

[TroyBranch]

My suggestions:

1. Check all your wiring to ensure that there are no sharp bends or pinches anywhere. A pinch or shard bend could easily be affecting more than one wire.
2. Do you have the circuit breaker values on the VPX set to appropriate levels?
3. How many devices do you have connected to each VPX output? Ideally just one device per output.
4. On the ground, replace the power source feeding the VPX with an adjustable power supply. Then start changing the supply voltage from 13V down to less than 10V and see if the behavior is similar to what you see while flying. You supply voltage could be fluctuating or you battery is going bad.

There are hundreds of VPX devices flying every day. They are quite robust and your experience does not appear to correlate with other peoples experiences with these devices. Your failure mode is not consistent with the way the VPX works so it would seem the problem is likely outside the VPX.

1 yes I looked at all of them. It’s a clean install. I have built 5 planes and this was my 6th panel.
2 the values are right.
3 one per output.
4 The logs show no voltage drop. I can try that.

There is one other that had the exact same issue on the avionics switch. They tried everything, ended up installing breakers for avionics. It was a reputable avionics shop. It would be nice if they chimed in.

 

[graywoodworking]

No they are in 3 different connectors. The only constant is they are on switch 3.

I have had some issues with toggle switches. A few months ago I was experiencing some autopilot abnormal disconnects. I replaced the switch for the autopilot and I haven't had any issues since. The toggle switches I purchased from Stein are rated for 125V and a lot of amps. An electrical engineer friend of mine suggested that the logic level signals that are switched on/off in the VPX-Pro do not have enough current to keep the switch contacts clean and they can become intermittent. I also have replace toggle switches for some of my lights over the past couple years.

 

[TroyBranch]

Just did a 40 min flight and had no issues. With all the avionics set to always on, I just shut them off before start and then turned them on after start through the VPX. I will fly it this way for a while and see. But last time I had multiple failures on a flight, the failures happened on the next flight too. If it keeps working this way I could try a new switch but that did not solve it for the other that had this same issue. I think I will be going to breakers on the avionics like they did as I just don’t trust it. The worst is that when you think you solved it, it takes so long to show up again. Breakers will remove that worry.

 

[TroyBranch]

I have had some issues with toggle switches. A few months ago I was experiencing some autopilot abnormal disconnects. I replaced the switch for the autopilot and I haven't had any issues since. The toggle switches I purchased from Stein are rated for 125V and a lot of amps. An electrical engineer friend of mine suggested that the logic level signals that are switched on/off in the VPX-Pro do not have enough current to keep the switch contacts clean and they can become intermittent. I also have replace toggle switches for some of my lights over the past couple years.

That makes sense. The other that had the same issue tried other switches but they could not get it to be stable. When they bypassed the switch it worked. They could not leave it that way so they installed breakers. It’s a very critical item and I can’t have that worry in the future even if I get it to work with a new switch for a while. Going IMC and worrying about the navigator failing is not much fun.

 

[georgemohr]

That makes sense. The other that had the same issue tried other switches but they could not get it to be stable. When they bypassed the switch it worked. They could not leave it that way so they installed breakers. It’s a very critical item and I can’t have that worry in the future even if I get it to work with a new switch for a while. Going IMC and worrying about the navigator failing is not much fun.

If that person had the switches on a common ground (remember these switches are active-low), a problem with that common ground would really explain it....

 

[RVbySDI]

If it was that, why would it work when bypassing the vpx and using the exact same wires/connectors.

Because it very well could be a bad connection between that pin in that wire with the receiving female pin in the connector. By removing it from the original connector and singularly connecting it to a new connection outside of the original connector you BROKE the intermittent connection that was failing and replaced it with good contact finally.

Use an OHM meter on all your connections as was mentioned above. It is a given that you can just rewire everything and potentially remove the offending problem. If that is your choice, it should work, but finding the root cause is important for many reasons. Do as you desire, it is your airplane. But simply replacing components does not necessarily mean problems are fixed.

I am with Walt. It sounds to me there is a bad power or ground connection at the main power connection, or the power or grounds from the instruments to the VPX. If you were to cut off the pins feeding into the VPX for the main power and ground from the battery, and/or from the instruments, then crimp new ones on that could potentially resolve the problem. However, before doing so, OHMing out the power and ground circuits from end point to end point is the really true test for locating the issue.

 

[TroyBranch]

If that person had the switches on a common ground (remember these switches are active-low), a problem with that common ground would really explain it....

Unfortunately I don't have enough information as to what they did. I will check that ground as well. The other part that cannot be explained is why only some items on the avionic switch cycling? Its not like the switch is killing all power like when you shut the avionics switch off.

 

[georgemohr]

Unfortunately I don't have enough information as to what they did. I will check that ground as well. The other part that cannot be explained is why only some items on the avionic switch cycling? Its not like the switch is killing all power like when you shut the avionics switch off.

The only thing I can offer to explain that is the internal capacitance of the device and its ability to keep power through a very short "blip"? Perhaps in an unpredictable way? Just guess here....

 

[TroyBranch]

Because it very well could be a bad connection between that pin in that wire with the receiving female pin in the connector. By removing it from the original connector and singularly connecting it to a new connection outside of the original connector you BROKE the intermittent connection that was failing and replaced it with good contact finally.

Use an OHM meter on all your connections as was mentioned above. It is a given that you can just rewire everything and potentially remove the offending problem. If that is your choice, it should work, but finding the root cause is important for many reasons. Do as you desire, it is your airplane. But simply replacing components does not necessarily mean problems are fixed.

I am with Walt. It sounds to me there is a bad power or ground connection at the main power connection, or the power or grounds from the instruments to the VPX. If you were to cut off the pins feeding into the VPX for the main power and ground from the battery, and/or from the instruments, then crimp new ones on that could potentially resolve the problem. However, before doing so, OHMing out the power and ground circuits from end point to end point is the really true test for locating the issue.

I will be checking all the grounds again. I agree that is sounds like a bad connection, but why is the VPX not showing it up as fault if it was. I thought that was the benefit of the VPX to help find these issues.

 

[georgemohr]

I will be checking all the grounds again. I agree that is sounds like a bad connection, but why is the VPX not showing it up as fault if it was. I thought that was the benefit of the VPX to help find these issues.

VPX "Fault" behavior is exclusively an over-current indication. I dont think it knows or cares much about the ground or wiring beyond that.

 

[DerekS]

Unfortunately I don't have enough information as to what they did. I will check that ground as well. The other part that cannot be explained is why only some items on the avionic switch cycling? Its not like the switch is killing all power like when you shut the avionics switch off.

If memory serves.... I believe I read (enough wiggle words yet?) that there is a short delay between switching (100ms comes to mind) when switching multiple devices, so a very short interruption on the avionics switch could potentially be back on before it switched all the devices off so only one or two devices would cycle.

 

[jjb]

VPX "Fault" behavior is exclusively an over-current indication. I dont think it knows or cares much about the ground or wiring beyond that.

To expand on the above, a VPX circuit fault where the VPX turns off the circuit can be caused by any one of three conditions, only one of which is an over-current:

1. A short to ground, either permanently or momentarily
2. An over-current condition (as noted above)
3. A current fault, where a device is turned on but is drawing less than 100 milliamps for 3 seconds. (This one can be enabled or disabled by the user)

Refer to the VPX installation manual, Section 10-7, on Page 70

Current fault detection can cause nuisance trips on some devices, which is why the VPX installation manual specifically recommends disabling this option for installed avionics. See Section 6.9, on Page 57

 

[riseric]

FWIW, one data point.
I had the fault detection enabled on the Dynon Heated Pitot...
Since that device cycles on/off, VPX detected a current drop and tripped the circuit...
Disabled the fault detection and voilà !!! No more tripped circuits.
Other than that, my VPX is working as expected.
Best of luck in resolving your issue.

 

[stigaro]

FWIW, one data point.
I had the fault detection enabled on the Dynon Heated Pitot...
Since that device cycles on/off, VPX detected a current drop and tripped the circuit...
Disabled the fault detection and voilà !!! No more tripped circuits.
Other than that, my VPX is working as expected.
Best of luck in resolving your issue.

Good point about the current fault detection. As I recall, this feature is only useful for constant current draw devices. A COM is certainly not constant current and if enabled, could certainly cause a shutdown when transmitting. NAV, I honestly don’t know.

 

[Mich48041]

Troy wrote, "No they are in 3 different connectors. The only constant is they are on switch 3."

I am not familiar with the VPX. Is the switch that you are talking about a software switch internal to the VPX or a mechanical switch? If it is a mechanical switch and only switches a low current input to the VPX, then like Larry Gray posted, the current is not great enough to keep the switch contacts clean. The solution is to replace the switch with one with gold contacts.

 

[RV10inOz]

If you have a Plane Power alternator replace it. I guarantee that is the problem. And when I say replace it, I mean with a B&C.

We have replaced dozens down here with ALL THE SAME SYMPTOMS.

High amounts of ripple from a faulty built in rectifier/regulator. Notchy supply in voltage swings results in similar current swings. The VPX thinks this is a short circuit, even reports it as such.

I would be extremely surprised if the fault is anything else. Now if you have a B&C then you do have a tricky thing to fault find as they rarely if ever give trouble.

 

[TroyBranch]

I am not familiar with the VPX. Is the switch that you are talking about a software switch internal to the VPX or a mechanical switch? If it is a mechanical switch and only switches a low current input to the VPX, then like Larry Gray posted, the current is not great enough to keep the switch contacts clean. The solution is to replace the switch with one with gold contacts.

The switch is separate to the VPX. You wire to say switch 3 input pin in the VPX and then you can choose which items switch 3 turns on by picking switch 3. I changed all my switch 3 (avionics) to “always on” so the switch is not doing anything. One flight down with no issues since the change. If these contacts won’t stay clean because of the low current, it’s does not sound like a safe way to wire an avionics power.

 

[rsultzbach]

That makes sense. The other that had the same issue tried other switches but they could not get it to be stable. When they bypassed the switch it worked. They could not leave it that way so they installed breakers. It’s a very critical item and I can’t have that worry in the future even if I get it to work with a new switch for a while. Going IMC and worrying about the navigator failing is not much fun.

Remember, if you are IFR and you have a navigation problem, just tell ATC you need vectors and or altitudes and fly the plane. Once safe and stable, then you can trouble shoot your system. I would only trouble shoot in a controlled manner and only briefly checking a rudimentary cause and effect.

 

[Mich48041]

it’s does not sound like a safe way to wire an avionics power

That is why Bob Nuckolls does not recommend an avionics switch. If it is not installed, it can not fail.

 

[Walt]

That is why Bob Nuckolls does not recommend an avionics switch. If it is not installed, it can not fail.

Are you kidding? So a single source custom computer running your entire electrical system is ok but not a simple ultra reliable avionics switch??
(PS: Logic switches are not the same as load switches, they should have gold contacts.)
I’ve been requested to install VPX for the guy who feels like he needs all the ‘features’,….. my response, time to go elsewhere as I won’t install a panel with VPX.

 

[TroyBranch]

Remember, if you are IFR and you have a navigation problem, just tell ATC you need vectors and or altitudes and fly the plane. Once safe and stable, then you can trouble shoot your system. I would only trouble shoot in a controlled manner and only briefly checking a rudimentary cause and effect.

Agreed. The one thing this has given me is great training or maybe I should say testing of my flying. How often do you have to trouble shoot real world electrical issues. Even when I had an issue while IMC I had the iPad ready even though I use the plates on the G3X.
When the approach got corrupted and when I went to add the approach back in, it was not on the right airport anymore in the 750. The approach plate was gone on the G3x too. I had to get the airport back in and reselect the approach. It didn’t take long to do but it made it a bit task saturated. I was still several minutes from the initial fix and I was handed off from centre for the local airport frequency. My next step was to go back with centre but I solved it quick enough I just continued as the approach never changed. What a test it was…..

 

[TroyBranch]

So a computer running your entire electrical system is ok but not a simple ultra reliable avionics switch??
PS: Logic switches are not the same as load switches, they should be gold contacts.

Yes Walt, I never liked the idea either, so many use it so I figured why not. I am changing the avionics to breakers no matter the outcome. I can’t have switch contacts failing again later on. Not knowing when it is going to happen is not very fun.

 

[TroyBranch]

Troy I'm assuming that all your devices are connected to the same "Avionics Master" switch behavior in the VPX right? So if the toggle switch was faulty it would probably cycle all the devices at once, yes?

Yes. As someone mentioned certain avionics could take longer to be effected by a power loss so not all are shutting off.

 

[lr172]

. I am changing the avionics to breakers no matter the outcome. I

I think that is a wise idea. There is a place for computer control, but one must balance the risk reward.

 

[wirejock]

This is outside the box, but can you swap pins/devices somehow and see if the problem follows the pins or stays with the device?
Just another test option

 

[rocketman1988]

Yes Walt, I never liked the idea either, so many use it so I figured why not. I am changing the avionics to breakers no matter the outcome. I can’t have switch contacts failing again later on. Not knowing when it is going to happen is not very fun.

I understand your choice but consider this; If the VPX was a systemic problem, don’t you think there would be far more problems with the many people running the VPX? Especially since you had two fail in exactly the same way?

Just saying…

 

[georgemohr]

I understand your choice but consider this; If the VPX was a systemic problem, don’t you think there would be far more problems with the many people running the VPX? Especially since you had two fail in exactly the same way?

Just saying…

I think he has some good debugging steps to try

1) Fly with the avionics "always on"
2) Fly with the avionics slaved to a different rocker switch

If both of those work, the issue is the AV master switch or associated wiring. OP if at that point you still want to do a VPX-tomy (LOL) that's your choice.

-G

 

[TroyBranch]

I understand your choice but consider this; If the VPX was a systemic problem, don’t you think there would be far more problems with the many people running the VPX? Especially since you had two fail in exactly the same way?

Just saying…

I am not the only one though. Others have said they had issues with switches, they changed them and it has been fine…for now until the contacts become an issue again as the Vpx is two sensitive to the contacts. They were just lucky it was not on the avionics. The other case was with the same exact issue as me cycling power on the avionics.
When you have one of the most important items go black while IMC you do whatever is required to ensure it will never happen again. I can loose power to anything else and be fine and I have IBBS flow through for the G3X system. Maybe the solution is to have all the avionics flow through an IBBS as well. That is a future plan but it will still be on breakers with the IBBS for extra back up.

 

[dmattmul]

Yes Walt, I never liked the idea either, so many use it so I figured why not. I am changing the avionics to breakers no matter the outcome. I can’t have switch contacts failing again later on. Not knowing when it is going to happen is not very fun.

Any chance you want to sell either of your VPX's? (Maybe bring down to SNF?)

 

[TroyBranch]

Any chance you want to sell either of your VPX's? (Maybe bring down to SNF?)

LOL! No, always wanted the second for backup, heard bad storeys of people getting stranded with a failed one. I will still be using it, just not for avionics.

 

[bkervaski]

LOL! No, always wanted the second for backup, heard bad storeys of people getting stranded with a failed one. I will still be using it, just not for avionics.

That can be said about anything ... the VPX Pro (vs the older models) has been building a very reliable track record.

 

[Mich48041]

Are you kidding? So a single source custom computer running your entire electrical system is ok but not a simple ultra reliable avionics switch??
(PS: Logic switches are not the same as load switches, they should have gold contacts.)

Walt, I am on your side. I would not put a VPX in my plane either. However, it is not the VPX fault that the OP installed the wrong switch, one with silver contacts instead of gold contacts.

 

[Mich48041]

Troy, regardless if a VPX or circuit breakers or fuses are used, an avionics switch is the weak link in the system. Having an avionics switch puts all of the eggs in one basket. There is no good reason to have an avionics switch unless your avionics were made prior to 1970. Read what Bob Nuckolls says about having an avionics switch.
http://www.aeroelectric.com/articles/avmaster.pdf

 

[georgemohr]

One of the good features of the VPX is the ability to override that AV Master switch (or any switch) from the G3X.

 

[georgemohr]

I am not the only one though. Others have said they had issues with switches, they changed them and it has been fine…for now until the contacts become an issue again as the Vpx is two sensitive to the contacts. They were just lucky it was not on the avionics. The other case was with the same exact issue as me cycling power on the avionics.
When you have one of the most important items go black while IMC you do whatever is required to ensure it will never happen again. I can loose power to anything else and be fine and I have IBBS flow through for the G3X system. Maybe the solution is to have all the avionics flow through an IBBS as well. That is a future plan but it will still be on breakers with the IBBS for extra back up.

Regarding running the GTN off an IBBS as a backup, be aware that the IBBS doesn't have very high current capability. When we did our panel planning, we discounted the use of the IBBS to run the 650 mostly due to the Comm xmit amp load. However it does seem that the GTN allows two separate power circuits; one for the Nav side and one for the Comm side. It might be possible to run only the Nav side off the IBBS as a backup, but you'd want to prove that with Garmin first.

 

[TroyBranch]

That can be said about anything ... the VPX Pro (vs the older models) has been building a very reliable track record.

True, but the vpx is definitely going to make me stranded if it completely goes down. It’s worth it to me. My friends know I have a spare so it’s good for them too.

 

[TroyBranch]

Regarding running the GTN off an IBBS as a backup, be aware that the IBBS doesn't have very high current capability. When we did our panel planning, we discounted the use of the IBBS to run the 650 mostly due to the Comm xmit amp load. However it does seem that the GTN allows two separate power circuits; one for the Nav side and one for the Comm side. It might be possible to run only the Nav side off the IBBS as a backup, but you'd want to prove that with Garmin first.

I never looked into either, maybe a no go. It was just a thought when I was typing….

 

[TroyBranch]

That’s about as close to isolating the VPX as you can get. Pull the pin, get a new wire with the mating pin and a fuse, connect the pins to each other and shrink tube with the other end connected to power through the fuse.

The only other thing is the switch input wiring, but if you set that output always on then it should ignore the switch input.

Given the above, I think you are down to the following:

1. The pin wasn’t fully inserted in the vpx connector but you bypassed that and now it works.
2. The pin has a poor crimp that works outside the housing for whatever reason. (Can we get a picture of this pin?)
3. The wire has a break, and moving it slightly made contact.
4. The VPX is bad internally or perhaps its connector is faulty.

If it were me, I would put a new pin on the end and focus on machine like perfection then carefully insert making sure that the depth and orientation was right, then I’d disable the switch and make it always on.

If that didn’t fix it, I’d inspect the wire real good, and if it was fine, I’d remove the VPX.

1 The pin was inspected prior to removal. It was inserted correctly.
2 The crimp was fine as it it is the same crimp on the fuse test set up.
3 I am using the same wire and it works fine.
4 Don't know.

Just to clarify, I made this change only on Nav 2 as that is where the problem started. The change to a fuse has not had an issue since it was done in July. This latest failure was nav/com 1 and the com on Com 2. Those pins are still in the VPX.

 

[TroyBranch]

Troy, regardless if a VPX or circuit breakers or fuses are used, an avionics switch is the weak link in the system. Having an avionics switch puts all of the eggs in one basket. There is no good reason to have an avionics switch unless your avionics were made prior to 1970. Read what Bob Nuckolls says about having an avionics switch.
http://www.aeroelectric.com/articles/avmaster.pdf

Without an Avionics switch, I would get a huge voltage drop on start up and likely reset them every time. That can't be good for the units. I would need a completely separate power supply to the avionics.

 

[JDA_BTR]

As to having or not having an avionics switch. I dislike having my avionics brown out during start. They may be fine but it just feels wrong. Now that I have an EarthX battery there is no brown-out because the battery keeps voltage at high load, so maybe I'd do different based on that. But I like having all of it off for start.

 

[TroyBranch]

One of the good features of the VPX is the ability to override that AV Master switch (or any switch) from the G3X.

How do you override it? You have to do the "always on" with a computer first then you can turn it on or off from the G3X. If you don't change the always on you are not bypassing the switch. Is that what you mean?

 

[TroyBranch]

Walt, I am on your side. I would not put a VPX in my plane either. However, it is not the VPX fault that the OP installed the wrong switch, one with silver contacts instead of gold contacts.

So all my switches that tie to the VPX are wrong then. Will a gold switch stay clean over time with the low current? Sounds like I need to change all them now too as they will likely be the next problem.

 

[Walt]

So all my switches that tie to the VPX are wrong then. Will a gold switch stay clean over time with the low current? Sounds like I need to change all them now too as they will likely be the next problem.

Let me guess, pretty looking rocker switches?

 

[TroyBranch]

Let me guess, pretty looking rocker switches?

Yes, Can you send a link for a switch with an actual gold contact? I can only find silver.

 

[Walt]

Yes, Can you send a link for a switch with an actual gold contact? I can only find silver.

Not it a pretty looking rocker switch!!
There may be some, but I've never looked as I exclusively use MIL spec toggles mostly.
There are toggles available with gold contacts.

 

[TroyBranch]

Not it a pretty looking rocker switch!!
There may be some, but I've never looked as I exclusively use MIL spec toggles mostly.
There are toggles available with gold contacts.

I just mean the toggle. I can't find a source for the toggle being gold contacts.