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  #1  
Old 04-04-2021, 06:16 AM
david.perl's Avatar
david.perl david.perl is offline
 
Join Date: Dec 2010
Location: Watford UK
Posts: 125
Default Werd issue with transponder tripping when LED lights put on with VPX Pro

hi

Ive been flying my RV7 with a vpx pro with no issues for 300 hours

after a 2month lockdown hiatus i flew the aircraft a couple of times

ive got an odd condition developed

the transponder shows a short fault when the engine is below 1000rpm and when i switch on the LED nav/strobe and landing lights

if i reset in the air and the turn the lights on, the TX stays on

on landing, when cutting the engine to below 1000rpm it trips again

voltage on alternator is steady at 14.5volts

only thing new in last few months is i installed an ADSB conspicuity device

any suggestions?
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  #2  
Old 04-04-2021, 06:35 AM
Avanza Avanza is offline
 
Join Date: Jul 2020
Location: Vastervik Sweden
Posts: 57
Wink TXP issue

You need to tell us more about the installation.
Please be specific about equipment txp/ adsb/ nav.
The more details we have the better.
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  #3  
Old 04-04-2021, 06:52 AM
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david.perl david.perl is offline
 
Join Date: Dec 2010
Location: Watford UK
Posts: 125
Default

Its a VPX Pro

Transponder is a dynon - its a rebadged trig transponder Dynon SV-XPNDR-26x

ADSB installed is a Pilot Aware - its a uk sold device https://www.pilotaware.com/

LED lights are from AeroLED's

let me know what other info would be useful

Other thing i think ive noticed is slight alternator whine when engine is on tickover - maybe its been there longer, im not sure
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  #4  
Old 04-04-2021, 02:20 PM
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GalinHdz GalinHdz is offline
 
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Location: KSGJ / TJBQ
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Default

What size alternator do you have? 35A, 60A, 70A? How much total current (amps) is being drawn below 1000rpms?
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  #5  
Old 04-04-2021, 02:32 PM
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david.perl david.perl is offline
 
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Default

60 amp plane power

on the VPX display on the dynon the total power consumption can be no more than 30 amps ,

if the current consumption was over the capacity of the alternator, why would the transponder trip showing a short circuit?
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Last edited by david.perl : 04-04-2021 at 02:35 PM.
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  #6  
Old 04-04-2021, 03:52 PM
Peter Costick Peter Costick is offline
 
Join Date: Jan 2005
Location: Melbourne, Australia
Posts: 112
Default

Hi David

First thing I would be doing would be thinking about what has changed. Maybe disconnect the new adsb device and retest.

Also maybe cut power at altitude and see if the same fault occurs, so is it tied to the rpm of the engine.

On a different note I see you are based near Watford, 20 years ago I used to live near there and flew out of Elstree..happy memories 😊
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  #7  
Old 04-04-2021, 04:04 PM
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wirejock wirejock is online now
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 4,373
Default Grounds

First thing I would do is disconnect the last install and check the grounds. Sounds like a ground problem to me.
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Donated 01/01/2021, plus a little extra.
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  #8  
Old 04-04-2021, 04:13 PM
Aussieflyer Aussieflyer is offline
 
Join Date: Jan 2015
Location: Redcliffe, Queensland, Australia
Posts: 83
Default Regulator Spike

I and several friends suffered the same. We all had Plane Power 60amp Alternators. Connect an oscilloscope and you will note a dirty spike in the regulator charge rate. The VPX interprets the dirty spike as an overload and trips the transponder to protect it.
Replace the regulator or alternator, we are all using B & K alternators now with no issues.
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  #9  
Old 04-17-2021, 05:36 AM
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david.perl david.perl is offline
 
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Location: Watford UK
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thanks aussie flyer, sounds like that might be the issue

Ive noticed other devices are also tripping when the load is increased

if the alternator field wire is turned off, everything stays on even with every device turned on
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  #10  
Old 04-17-2021, 05:37 AM
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david.perl david.perl is offline
 
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Quote:
Originally Posted by Aussieflyer View Post
Replace the regulator or alternator, we are all using B & K alternators now with no issues.
do you know what the direct replacement is for the plane power 60 amp?
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