FrSky DHT DIY in JR module case?

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FrSky DHT DIY in JR module case?

Postby csurf » Wed Sep 25, 2013 9:48 pm

I want to clean up the wiring inside my 9x, and I no longer really like the idea of cramming my FrSky DHT DIY Tx module inside the main radio housing & having it hard-wired to the radio pcb. If I could go back in time, I would have simply bought the DJT model which plugs nicely into the radio without having to solder or stuff anything inside the 9x.

I've seen that you can order bare plastic JR-type Tx module cases online, and Im wondering if it would be possible to setup a DHT module inside one of these cases. Has anyone tried doing something like this?

I think the biggest problem might be the layout for the radio pins that plug into the Tx module, since the DHT appears to have these input headers in a different location, correct? Still, could it be made to work by somehow relocating the Tx plug inputs? Anyone have any ideas on how this could be accomplished?
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Re: FrSky DHT DIY in JR module case?

Postby ShowMaster » Thu Sep 26, 2013 12:28 am

If you haven't removed the metal V in your 9x case please do. It'll free up room to better mount your DJT. Shortening all the DHT wires will also help.
As for the module mounting idea, can't help but you'll still have the antenna mount to deal with and I'm not sure the board will easily fit.
I too have one 9x with the internal DHT because I blew up the DJT modifying it 3 years ago and only had a DHT left. I just left it that way and will probably sell the working 9x with telemetry for hopefully cost of parts or for parts.
Good luck and I'll be looking for your progress posts.
I just remembered from a year ago...
I've actually mounted a DHT internally for a friend wanting 16 channels and after carefully cleaning the wiring and removing the metal unused V strap I had ok room and he's happy.
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Re: FrSky DHT DIY in JR module case?

Postby csurf » Thu Sep 26, 2013 6:12 am

thanks for the tips!
So, that giant, v-shaped, ground-lever-thingamajig can be removed without any negative consequences?

I was thinking about just mounting the antenna to the plastic JR module case just like a normal DJT has its antenna mount.

Another reason why I'd like to be able to remove the FrSky Tx is in case I'd like to try to setup 'beater' models with cheaper Rx's (such as the Turnigy stuff), so it would be cool to just swap out the FrSky Tx and pop in the Turnigy or whatever, and not have to worry about opening up the radio and disconnecting the DHT. Plus, getting the Tx out from inside the case makes it easier to do mods and stuff without having the DHT get in the way and worrying about damaging it somehow.

I'm going to try to find one of those bare cases on ebay and we'll see how it goes.
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Re: FrSky DHT DIY in JR module case?

Postby ShowMaster » Thu Sep 26, 2013 7:26 am

The V is left over from the prior FM frequency setup. It ties the front and back case grounding system together to form a better counterpoise rf grounding system.
The long antenna was only 1/2 of the antenna system, your hands and body was the other half.
The 2.4 antenna system takes care of that now and has no use for it.
About switching modules, good luck but think about just a new DJT. The DJT is setup with the antenna mounted nicely and easy to interface the telemetry.
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Re: FrSky DHT DIY in JR module case?

Postby adagiohr41 » Thu Sep 26, 2013 1:07 pm

I removed the "V" and needed to add a separate ground wire attachment between the main PCB and the switch board mounted on the back cover. My 9X was an early one and this might not be the case for later units. Just an FYI ....
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Re: FrSky DHT DIY in JR module case?

Postby ShowMaster » Thu Sep 26, 2013 2:44 pm

I'm confused by you having to add a wire?
No way should the ground be carried through just with a pressure contact like the V for the electronics.
It's unreliable as a solid connection for power ect.
I'm glad you added the wire because your tx could have developed trouble as time went on if just the v was the ground connection.
Was this a hobby king 9x or an actual FkySky 9x and what was the year you bought your tx?
Of course to be sure and safe ill modify my recommendation.

Separate the case halves leaving without unplugging and connectors and verify that the case front and rear grounds are carried through using your ohm meter. They should be and at that point remove the V to make more room.

The V has been removed in 12 9x conversions by me so far also involving 3 sky9x board as some of them.
So far no issues.

Thanks for heads up as it's something one should double check. Adding a new ground wire would still free up the space the V takes up. If it came to that I'd add a connector inline so the case halves could separate totally when needed.
Then again, using the DJT module doesn't require any extra internal case space and the V is a non issue?

.
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Re: FrSky DHT DIY in JR module case?

Postby csurf » Fri Sep 27, 2013 1:41 am

I removed the V, and it *seems* to be working OK for now, will need to test further&confirm.
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FrSky DHT DIY in JR module case?

Postby ShowMaster » Fri Sep 27, 2013 3:43 am

Good to know.
Tx grounds are carried by wires in the large connector from the backplane to the main motherboard. You shouldn't have any issues.
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Re: FrSky DHT DIY in JR module case?

Postby adagiohr41 » Sun Sep 29, 2013 12:38 pm

ShowMaster wrote:I'm confused by you having to add a wire?
No way should the ground be carried through just with a pressure contact like the V for the electronics.
It's unreliable as a solid connection for power ect.
I'm glad you added the wire because your tx could have developed trouble as time went on if just the v was the ground connection.
Was this a hobby king 9x or an actual FkySky 9x and what was the year you bought your tx?
Of course to be sure and safe ill modify my recommendation.

Separate the case halves leaving without unplugging and connectors and verify that the case front and rear grounds are carried through using your ohm meter. They should be and at that point remove the V to make more room.

The V has been removed in 12 9x conversions by me so far also involving 3 sky9x board as some of them.
So far no issues.

Thanks for heads up as it's something one should double check. Adding a new ground wire would still free up the space the V takes up. If it came to that I'd add a connector inline so the case halves could separate totally when needed.
Then again, using the DJT module doesn't require any extra internal case space and the V is a non issue?

.


Sorry for the posting delay. The 9X was one of the first ones sold and the FrSky was also the same vintage. And I did add a connector for the ground wire. The tip off that this wire was needed is that the LCD display wouldn't power on when the "V" was removed. I've also checked the continuity from the large connector to the RF/switchboard and all wires are good. So my troubleshooting stopped when the additional ground wire was enough to solve the problem. Just a note ... I would love to have a 1 foot jumper wire that replaces or extends the cable connecting the back halve of the transmitter to the front. I've had to re-solder wires on that cable a few times already.
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Re: FrSky DHT DIY in JR module case?

Postby ShowMaster » Sun Sep 29, 2013 3:07 pm

Extending the wires probably isn't a good idea. Longer isn't better when mixing data and RF and the having excess wire. This can add inductance and capacitance and posable internal crosstalk.

Just a thought since your radio shouldn't have connection issues and was an early version, maybe buy a new FlySky version or Turnigy and start over. Without a good tx you can depend on it pretty much runes the hobby fun.
To be honest, I've built up and modified many 9x and never had your wiring or wire breaking issues. I have repairs several others with a reversed battery as well but even they didn't need the V .
I did repair one assumed new Turnigy that arrived with wiring cut and redirected from HK. The owner got all his money back from HK since it was a mess inside. I cleaned it up like new and removed the V and he's flying it without issues now. I also repaired a 9x with a lot of water damage from HK that was also new. The owner also got his money back. I had to replace every toggle switch on it and it too is still flying.
Point here is that your tx can be rewired to what it should be if your soldering is good and you're good with a meter. If not and it's in trouble maybe try a new 9x, FkySky is my favorite because it's the real deal from FkySky, not a Made for HK version.
Too bad we're not neighbors.
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