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Jun 05, 2016, 11:29 PM
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markm75's Avatar
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HMDVR Mini DVR Headplay Goggles Mod issue with diagonal lines - interference?


I'm having an issue after doing my Headplay HD Goggles mod (full article also here).. where Im getting interference in the image.


I had diagonal lines in the headplay main av1 image as well at first.. i tore apart things and eliminated most of the lines in 1.3ghz and 5.8.. I swapped av1 for av2.. so now the Mini DVR is on AV1 rather than av2 for playback at least.. but still spliced into my main leads for the AV signal.

Turns out though, i think, the swap of the port wasnt the fix, but rather just adjust wiring positions.

So i'm wondering if this interference is the result of maybe needing copper shielding tape (like I used for the x380 gps shielding).. or maybe an LC filter.

I tried a larger RMRC LC filter from the main battery but that didnt help.

I did see that someone put a small LC filter just at the power point for the MiniDVR with some success.. but i'm unsure what capacitor or parts i need for that (wiring?).

Also including a video (raw / unedited) showing the lines.
*You dont see this in the goggles view, even though the dvr and goggles view output are spliced off the same lead

Any thoughts out there or other suggestions to try, prior to tearing the goggles apart again and moving wires around at least.


Thanks in advance

HMDVR Mini DVR Recording Twinstar II - RAW footage - Lines and Interference Example (10 min 0 sec)
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Jun 06, 2016, 09:43 AM
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markm75's Avatar
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Had some more specifics on what i've tried/heard..



I already tried using this LC filter from RMRC, just after the battery on the goggles.. but it didnt seem to do anything

I also saw they have this one (i guess the same but smaller, unsure)
Perhaps putting it where i have the JST that then goes to the HMDVR is best?


I also saw this on amazon, already with jst connectors, though $15, that looks like its worth a try


Another person said they use a 5v regulator.. i've never used one or know offhand how this gets wired, but i think an example of this is here
Appears that this wont work, i'm already using 5v from the goggles, its more to lower the voltage to 5v.
Last edited by markm75; Jun 06, 2016 at 02:17 PM.
Jun 09, 2016, 09:34 AM
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So i gave the amazon filter a shot

I put it just before the mini dvr (again, i had tried a bigger LC filter just after the battery before too).. same difference, no change.

Still some lines.

I guess the biggest thing i notice, is the quality of the playback mode (and the recording) is muddy.. not sure how else to explain it.. not very sharp (using my headplays av2 for playback/live view).. maybe this is "just how it is", and is expected, if so i'd let it go..

I was trying to wire just a video feed outside of my goggles into the dvr, to isolate and try it that way, so i took the git2 video out cable, wired the video to video, but i get nothing, not sure if it needs a ground somehow or what.

In this test the power would come from the goggles 5v.. but the video would be external, on the git2 cable, if i could get it to work.
Jun 10, 2016, 12:14 AM
Registered User
I had the same issues, and tried various LC filters also. I know some have solved this issue, but I could not. I believe it has to be tied to where you are tapping into the power and signal. I finally took mine off; would rather fly clean without the degraded image.
Jun 10, 2016, 10:40 AM
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Quote:
Originally Posted by Windlove View Post
I had the same issues, and tried various LC filters also. I know some have solved this issue, but I could not. I believe it has to be tied to where you are tapping into the power and signal. I finally took mine off; would rather fly clean without the degraded image.
How were you using the DVR, was it like me with a mod on the goggles (headplay hds?)

I put together this video to show the noise and also to show how the HMDVR clarity is pretty muddy compared to the RMRC Dvr.

I still think my noise on the dvr side comes from the 5v headplay feed, somehow, that maybe i need to tap into power from its 12v source via ubec.

I guess the real test would be to power the dvr off another 5v source outside of the goggles, while still sending video through the goggles, if the goggles + dvr still results in lines then it wasnt the power causing it. I'll try this later with my servo tester which outputs 5v.


Headplay-QuanumV2 Goggle Mods Build: Troubleshooting DVR Noise-Clarity and HMDVR vs RMRC (1 min 11 sec)
Mar 27, 2017, 08:45 PM
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VA6DX
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This might apply to this thread too. I recently had a buddy of mine work on this issue for me. I did a mod on my Headplays to pull out the internal vRX and added the Clearview Pro and a DVR (BTW, once you try Clearview, you'll never go back, well worth the expense). I was powering the Clearview Pro (mounted on the HPs) and HPs with the same battery and the lines drove me crazy. He reversed engineered the Headbox and this is what he found:

"There are 2 audio channels and the PCB simply has one Audio In label.

Anyway, I know what the problem is which is that the headplays switching power supplies create a lot of noise on the battery voltage and that the receiver relies on the DC Input ground lead for the video ground. This leaves all the battery voltage noise following through the DC ground lead which generates a noise voltage across the lead (due to its resistance) which then becomes added to the video signal.

There's only 2 ways to fix this. The easiest is to simply use a separate battery to power the receiver, but it would be so much nicer of course to have everything run off the same battery so I'll try to come up with something to use for the second solution, which is to use a filter on the receiver power leads to remove the noise.

As for why the headplay receiver doesn't have this problem - I'm guessing it's because it's powered from the head plays filtered 5VDC output. Switching power supply designs almost always include a filter that filters the output noise to a suitable level, but little attention is usually given to the noise that's generated on the DC input side as it's assumed anything else being powered by the same DC supply will also have a switching supply to supply it with filtered power like your receiver has (in this case, the Clearview Pro), although it doesn't help in this case with same ground being used for both, the receiver DC power and video output ground.

I was a bit surprised to see the video output jack ground not being used, although it wouldn't help much when both, the headplay and receiver, are powered from the same source as the video ground would be tied to the DC input ground somewhere inside the receiver. But for those that decide to use a separate battery to power each unit it would save having to run a ground wire to the DC input ground for the video ground needed rather than being able to simply use the video output cable shield.

Anyway, you may want to pass this on to everyone else that's having this problem to save them a lot of time and frustration as no amount of shielding or moving wires around is going to help and what's needed is to either use a separate battery to power the receiver or a proper filter to remove the noise on the receivers DC input power.

The fix:
A 100 uH inductor in the power lead to the external receiver clears up 99% of the lines. At first I thought it was 100% but if you look hard you can still see a few real weak ones at times which I believe are from the receiver itself. At least the ones from the headplay switching power supplies are gone."

This not only pertains to the Clearview, but any external receiver connected to AV2 (if you're seeing the diagonal lines.

Thanks to Barry VE6SBS for the fix.

Bear
Jul 07, 2017, 02:42 AM
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nonoze's Avatar
I have the exact same problem with all of the HMDVR i bought, and i bought like 10 of them, for various applications, mostly FPV planes, ground station recording, or just a simple camera-screen-recorder to test the performance of various CCTV and FPV cameras.

ALL of them have these exact lines that you got there! ALL OF THEM!

Tried every kind of filter, doesn't work! 100 uH inductor didn't work either.

I'm still working on it, that's the reason why i found this 1 year-old post, i'll keep you informed in case of positive results, who knows...

Other thing i've noticed is that they are REALLY FRAGILE!!! Hobbyking removed all negative comments about this product, but i can tell you i've burnt 50% of them, sometime just "using it" is enough...

5.5V instead of 5V: BURNT

LC filter connected the wrong way for 1 second: ghosting images forever

Using it for too long in a warm place: BURNT AGAIN!
Jul 07, 2017, 11:39 AM
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VA6DX
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Here's a website a fellow ham made for what he did to fix my interference problem. Some may find it useful: http://ve6atv.sbszoo.com/HeadPlay/default.htm
Jul 18, 2017, 07:50 AM
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nonoze's Avatar

Solved!


So, i tried:
- 5 kinds of 5V BEC,
- 1 voltage regulator
- 1 voltage + current regulator
And out of these 7 items, 2 instantaneously and totally got rid of the lines problem! No ferrite ring needed!
These are 1A and 3A 5V Micro-bec from hobbyking, maybe the cheapest ones! (see pictures)
So why does bigger and more expensive BEC result in these interference? Try to figure out...
(PS: Picture is all pink because IR filter has been removed for improved low-light performance)


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