9XR-PRO Hacks and Fixes

Post by **jhsa** » Thu Jul 17, 2014 8:59 am

Isn't the LCD the same as the old 9XR? I find mine very good.
But maybe I have a strange taste

João

SkyNorth · Post by **SkyNorth** » Thu Jul 17, 2014 1:03 pm

The Pro board was designed using the stock 9XR hardware..they both use the same LCD , as far as I know.
The Backlight may have been changed , if there is a colour / brightness difference .

The only way to tell , is to swap the LCD/backlight with your old 9XR , and see ...

-Brent

Post by **MikeB** » Thu Jul 17, 2014 1:11 pm

I may have one of these screens after all. When I started on the development I received a 9XR from HK, and the SKY boards from Brent. Later I got a Beta 'PRO. The displays are different, the 9XR one does look a bit "crisper".
I've tried changing a few LCD initialise settings, but nothing changes the look, I just need a different contrast setting to get to the same display level.
It may just be that HK have changed the display for both the 9XR and the 'PRO.

The backlight may be a different problem. On the 9XR, the backlight is driven from the battery supply via a 1K resistor, so the brightness will depend on your battery voltage. On the 'PRO it is driven from the regulated 5V via a 200 ohm resistor (R56). Assuming the backlight LED voltage is 3V, then 12V on the 9XR and the 'PRO should have about the same brightness of the backlight, although if the LCD is different, one may appear dimmer than the other. If it needs to be brighter on the 'PRO, then R56 could be reduced in value (say to 150ohms = Add a 560ohm resistor in parallel).

Mike.

mnementh · Post by **mnementh** » Thu Jul 17, 2014 2:50 pm

Does this mean the 9XR Pro uses an LCD that is pin-compatible with the one for the 9XR? I know the 9XR LCD is not pin-compatible with the 9x; I tried it when I got my 9XR. I was worried the reason they used this LCD was that they omitted the second connector on the Sky board for the improved LCD, and the only LCDs available are the old 9x style LCDs.

There IS a difference in the polarizing filter attached to the back of the LCD; the one on the 9XR is very visibly less opaque than the one on the 9x. I have yet to try a side-by-side comparison between the 9XR and the Pro LCD with both removed from the TX, however. I can do that.

I'll take mine apart and see if I can find you some part #s; if this LCD is SUPPOSED to be pin-compatible with the 9XR LCD, I'll try swapping them to see what difference it makes. I'll also investigate operating voltages and current draw on the backlight, which appears to be the same part between the 9XR and the Pro.

I've tried to make a photographic comparison of the two, but due to the nature of digital photography, it is nearly impossible to show what I'm talking about. The difference between the two is the same as the difference between the 9x with a HK backlight kit and the 9XR; in fact, my 9X is brighter than my 9XR Pro because I long ago modded it with an additional LED bar from a second HK backlight kit.

Like I said; it feels like I've gone back to using my old 9x, and that's NOT an exaggeration.

In order to make this the same brightness without overdriving the LEDs, I figure we'd need to add about 100-120 ma worth of additional LEDs; I'm not certain there's room in there for that, and I don't want to double the current draw of my TX just to get adequate illumination on the LCD. Then the question would be whether the Contrast ratio of this LCD is high enough to work with the additional lumens of (I'm just guessing here) 16 LEDs?

mnem
*Hoping we can resolve this*

Post by **jhsa** » Thu Jul 17, 2014 3:06 pm

maybe HK could make an upgrade kit with a white backlight
Blue tend to be darker in my opinion..
João

Post by **MikeB** » Thu Jul 17, 2014 4:07 pm

As I said above, I had a stock 9XR, and SKY boards from Brent, so it works with the stock 9XR LCD.
regarding the backlight, the 9XR used 12V and 1K, so only about 9mA (assume 3V across the LEDS). On the 'PRO, we have around 10mA (5V, 200ohms). Since the 5V is provided by a switch mode regulator, the backlight current from the battery is less than 10mA.

I've asked HK for clarification on the LCD and also the "Ball Bearing gimbals".

Mike.

mnementh · Post by **mnementh** » Thu Jul 17, 2014 10:46 pm

MMMhmmm...

Okay. I'll do some testing and report back with actual current draw vs brightness, and I'll scope out the actual LCDs for compatibility, maybe even a part # if I get lucky.

mnem
grr. arrg.

mnementh · Post by **mnementh** » Fri Jul 18, 2014 2:53 am

OK...

First results are:

The Pro LCD is DEFINITELY a different part from the 9XR LCD; I haven't found a part # on either LCD yet. The Backlights ARE the same part, same part #.

The 9XR LCD IS pin-compatible with the Pro; swapping the 9XR LCD and Backlight into the Pro resulted in lower brightness on the Pro, so hard to tell on the contrast. Pro LCD and Backlight in the 9XR resulted in much better brightness, but not as good contrast as the 9XR LCD.

I'm in the process of packing up my 9x; I've sold it. When I have more bench time, I'll scope out voltages and current draw.

Also, I've noticed a small hand-written tag in the battery box of my Pro - [ 299 ] ... Hmmmmm.
Peace!

mnem
*One more puzzle piece*

Post by **MikeB** » Fri Jul 18, 2014 8:27 am

I have a statement from Ivan at HK that the LCD is the same in the 'PRO and the 9XR, as are the gimbals. Production checking of the 'PRO includes checking the centering of the gimbals.

Mike.

mnementh · Post by **mnementh** » Sat Jul 19, 2014 2:16 am

I'll post pictures of the LCDs as soon as I can get back to my bench. DEF not the same part.

mnem
Watson, the game is afoot!

KAL · Post by **KAL** » Sat Jul 19, 2014 7:52 am

I don't know whether it is a common thing but when I put a blue backlight to my 9X,
contrast an sharpness were not very good. Results with white or green where even better.

I believe there were some threads here referring to this issue.

Klaus

Post by **jhsa** » Sat Jul 19, 2014 8:04 am

I have two 9x radios and I did order the blue backlight for both. The first one is really blue. The other one is much lighter and clear, and it does work better.. I don't know if the LED color was of a lighter blue, or maybe they sent a white BL by mistake

But it does work better.. I do like the dark blue one as well..

João

KAL · Post by **KAL** » Sat Jul 19, 2014 8:17 am

I bought a used 9x with white backlite. For my 2nd 9x which I ordered at HK I ordered a blue one.
So I could compare them side by side. Having seen the difference I soon ordered a white one ...

Just had some thoughts about changing the backlite color of my pro ...

Klaus

Post by **ShowMaster** » Sat Jul 19, 2014 8:28 am

I originally used a blue BL for all my 9x conversions. I found blue to be hard to read at times. I then tried a white BL and liked it much that's all I used later on. I still have several as spare replacements for club members 9x's I worked on.
I find my blue bk on my beta Oro to be much brighter than a new stock one a club member is using. After he has many good flights on his I've offered to open it up and we'll check a few things as well as soldering. One will be the BL, the other will be to open the speaker holes and maybe change the audio amp resistor.
I too would to own a retail version so I can see what's different.
SM

Sent from my iPod touch using Tapatalk, small keys and a big finger.

mnementh · Post by **mnementh** » Sat Jul 19, 2014 3:43 pm

Brent -

Is there an actual schematic diagram available somewhere for the release version of the Pro?

A quick Google only revealed the plug-in diagram you have posted here; not the schematic, and aside from the bootloader, the only hits I found on github were for OpenTX.

I'm mostly interested in the control circuit for display brightness. I need to know what is actually there, not what SHOULD be there based on the Sky board. Is there a series pass transistor in the circuit, or is it controlled directly by whichever analog output it is connected to on the processor?

Thanks,

mnem

Post by **MikeB** » Sat Jul 19, 2014 4:52 pm

Brightness is controlled using PWM. Transistor Q3 switches the 0V line through a 200 ohm resistor (R56). J15 has this signal and 5V on it.

Mike.

mnementh · Post by **mnementh** » Sun Jul 20, 2014 5:59 am

Mike - thanks.

Okay.. Then I've figured it out.

You were right, the 9XR drives the LCD backlights at 11ma; but that's 11ma EACH and there's 5 of them in parallel for a total of 55ma, which is EXACTLY what I get on my 9XR from a full pack. On the Pro that's 11ma/5 = 2.2ma per LED.

For this panel at a 5V source, that's 5V - 3.4V VF = 1.6V/0.055A =29.1Ω. Closest standard resistor is gonna be 33Ω 1/8W.

The LCDs ARE different; the polarized filter on the one from the Pro is noticeably darker and as you can see the ribbon cable is different.

That said, the difference in Contrast with the Pro LCD in my 9XR is NOTICEABLE; enough so that I'm going to keep the 9XR LCD in my Pro, but probably not enough that I'd buy a new 9XR LCD and take the gamble that I might wind up with EXACTLY the same part as came in the Pro if the different LCD was just a mid-production substitution.

[EDIT]

It would appear this is a moot point, as HobbyKing no longer offers the replacement LCD for the 9XR.

[/EDIT]

We'll see once I have a chance to replace the ballast resistor on the Pro. Since we do have a transistor in the circuit, I can do that. I might even investigate driving these LEDs to 15ma ea; typically these little SMDs are good for 20-25ma max, so still quite a bit of leeway. That will probably lighten up the shade of blue quite a bit as well.

Mike - since this circuit is controlled via PWM... maybe a 4.7-10uf cap across the LEDs to smooth out the ripple? Most of these LEDs will actually drive a lot higher current in pulsed mode though... 5 of 'em can probably handle more than Q3 can put out.

Thoughts?

Is the PWM frequency range low enough that flicker is a concern?

mnem
*Lit*

Post by **MikeB** » Sun Jul 20, 2014 7:52 am

The backlight PWM frequency is 100Hz and should be high enough to avoid flicker.

You say 5 LEDs in PARALLEL. Then they will share the current between them, so 2.2 mA each.

Mike.

mnementh · Post by **mnementh** » Sun Jul 20, 2014 2:41 pm

Mike -

Yes, that's what I said. For nominal brightness, we should be driving these at 10-15ma EACH with a VF of 3-3.4V. Right now, we're driving them at 2.2ma/2.667VF each on the Pro (with brightness at 100%).

The 9XR is driving the entire array at 55ma/3.007VF, (Actual measured current/VF) meaning each LED is driven at 11ma/3.007VF.

mnem
*Voltage Forward*

Post by **MikeB** » Sun Jul 20, 2014 4:03 pm

Going on the circuit I have for the 9XR, the backlight current is fed through a 1K resistor (R71). To get 55mA, you would need 55V, so what's different I wonder?

Mike.

mnementh · Post by **mnementh** » Sun Jul 20, 2014 4:33 pm

On my 9XR, R71 is 150Ω, which is right on the J2 connector for the LCD backlight. R60, right next to it, is 1KΩ. It's connected to J25 which I think is the [READY!] LED.

[EDIT]

Q3 is what, an MMBT3904 NPN, right?

[/EDIT]

mnem
*MOOP*

Post by **MikeB** » Sun Jul 20, 2014 4:49 pm

I just dug out the 9XR PCB I have and I see the same 150 ohms in position R71. This is probably the problem as brent will most likely have worked from te circuit that has the wrong value on it.
I'd say using a 150 ohm resistor is stressing the resistor. At 55mA, it is dissipating around 0.45W, and I doubt an 0805 resistor is rated for that!

So, on the 'PRO, R56 is 200 ohms, so probably needs to reduce to around 40 ohms to get around 50mA. You could wire a 47 ohm resistor in parallel, or replace it with a 39 ohm resistor.

Mike.

mnementh · Post by **mnementh** » Sun Jul 20, 2014 8:12 pm

Mike -

I've done some empirical testing based on my own calculations and replacing R56 with some standard resistors.

At 100% a 33Ω resistor yields 52.5ma total draw @ 2.94VF; this is 10.48ma/each LED. Calculated PD with 1.868 V dropped across R56 is 0.106W. This is pretty nominal compared to the 9XR, and appearance wise, so close to the same brightness that I can't tell the difference between the two.

At 100% a 22Ω resistor yields 67.4ma total draw @ 2.998VF; this is 13.48ma/each LED. Calculated PD with 1.625 V dropped across R56 is 0.121W. This is still well within typical max ratings of 20-25ma for these little SMD LEDs, and it is quite a bit brighter (and lighter shade of blue) than the stock 9XR; I have to turn it down to 75% to get the same perceived brightness. I LIKE it; ESPECIALLY with the higher contrast of the 1st Gen 9XR LCD in there.

: 1206 Size vs 0805 Size Resistor

Calculated PD says we should be able to use a 1/8W 0805 size SMD resistor, but it'll be right at the limits of its rating. However, due to a lucky fluke in the layout of the board, we can actually fit a 1206 size 1/4W resistor in there by soldering one end of it to the solder pad at the collector of Q3 and not have to make any modifications to the mainboard at all.

: R56 with 22Ω 1206 Size 1/8W Resistor

TL : DR Version:

My recommendation to those playing along at home would be to replace R56 with a 33Ω, 1206 size 1/4W resistor; this results in almost identical current draw and brightness to the tried and true original 9XR design, so should be similarly reliable. If you want to experiment with a brighter display, try a 27Ω or 22Ω 1206 size 1/4W resistor; that's what I'm using.

mnem
*Feeling Brighter*

mnementh · Post by **mnementh** » Sun Jul 20, 2014 8:57 pm

Mike, Brent -

I'm putting together a Mod Blog based on the above material; in it I pretty much ignore the different LCD used as it's really not different enough to be a deal breaker, and I concentrate on correcting the backlight ballast resistor. I place blame for the incorrect ballast resistor on a simple "clerical error". Do you have any issues with me publishing this?

Thanks,

mnem

Post by **MikeB** » Sun Jul 20, 2014 10:00 pm

Yes Q3 is a MMBT3904.
I have no problem with a blog of this change.
You could use a couple of 68 ohm 0805 resistors stacked on top of each other.

Maybe we can get production 'PROs changed as well.

Mike.

mnementh · Post by **mnementh** » Sun Jul 20, 2014 10:33 pm

Thank you sir!

Please try the Mod yourself; I think that once you SEE the difference you'll agree it's a MUST-HAVE revision that SHOULD be implemented ASAP.

I'll add your suggestion re: 2 68Ω 0805 resistors as well.

Complete Article is here: http://www.rcgroups.com/forums/member.php?u=428008

With this issue resolved, I'm loving my Pro again!

mnem
*Solid*

SkyNorth · Post by **SkyNorth** » Mon Jul 21, 2014 3:48 pm

Why not just just pull the wire from pin 1 on the LCD connector J15 and connect it to Pin 10 of J6
This will run the LEDs at the battery input voltage.

mnementh · Post by **mnementh** » Mon Jul 21, 2014 11:10 pm

Because then the LEDs will dim as the battery dies, and you'll be dropping 10-11V at 40-ish ma across a 1/8w resistor at R56, oh and... as long as it lasts, it still won't be as bright as the 9XR backlight is.

Replacing R56 is easier, now that I've done the R&D work.

[EDIT]

Crunching the numbers, with a fully charged pack at 12.6V, we get 9.4 volts/47ma dropped across the 200Ω resistor at R56. That's 442mW through a 125mW resistor. Definitely gonna let the magic smoke outta that.

And, for the few seconds it lasts, we're only driving the LEDs at approx 9.4mA each; it will still not be nearly as bright as the 9XR Backlight.

Replacing R56 is still better.

[/EDIT]

mnem
Watts up, doc?

fburden · Post by **fburden** » Tue Jul 22, 2014 4:55 am

Re. the LCD Backlight = "Underpowered", this has been a very interesting find. Nice Catch!

To be honest, lately I've been using my old 9X, no backlight installed, and I don't even miss it.
Actually I do not even want to be looking at my Tx while flying!!!!!!!!!!!!!! Voice is all I really need so I can hear the battery and RSSI numbers.

Farting around at night at home, sure the backlight comes in handy, but it's not a Show Stopper for me.

Even so, as I testor, that's a GREAT CATCH!!!

mnementh · Post by **mnementh** » Tue Jul 22, 2014 4:06 pm

I'm constantly fiddling with my TX programming; I'm a tinkerer. Added to that I'm terribly nearsighted... as in without my contacts, at arm's reach my fingers are just fuzzy pink sausages. This makes bright, clear text a MUST for me.

Also, if you're doing internal telemetry on the built-in screen, high contrast is an absolute must-have; it makes it possible to see the information you want with just a momentary glance, which is REALLY all you can spare. If you can't get that, it's useless.

Like I said; the one thing that kept me coming back to my 9XR over my much more heavily modified 9X was the clarity and crispness of the screen. It truly is a joy to behold. Now I have that on my 9XR Pro; so even though I'm now also a Taranis owner, I plan to keep my Pro.

mnem
*Joy in Mudville*

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Nice Catch! But is it really a Show Stopper??

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