FrSky issues recommended "fix" for DIY kit

[BlueSkyRoro]

Thank you so much! That would be very helpful !

Today I tried to measure a voltage between "Battery Minus" and " PWM Signal" coming out of my JR MC-16/20 radio using a analog meter . The result was approx.10V. (My battery voltage was about 11.8V at that time.....3slipo) Does that allow to conclude that this transmitter has probably a dangerously high signal voltage level ? ( Or does this voltage not at all correlate with the results of a proper measurement with a scope ? )

There's a friend of mine with the same transmitter who bought FRsky because of my recommendation and using the DIY module for ~8 flying hours now. Is it likely his module has already received some hidden damage and is there a way to find out ? ( From now on he could use the mod with the Schottky diode presented here....) I would hate to see him crash one of his models in the future because the FRSky DIY module secretly started smoldering ......

Cheers, Romano

[RCModelReviews]

If the module is still working it's unlikely to have sustained damage.

[kneedrag]

Chances are if your module is working still that your transmitter will not be one that will cause the overdrive to take effect. I have e-mailed all the customers in NZ who purchase kit through us and sent them a diode as a precaution. I have also sent a diode to a few people that have purchased there modules overseas. If you are in NZ and want a diode sent to you let me know.

[TG72]

Hello Bruce, you probable already know this, but I got a pm from Chase Wu from FrSky that the Diy telemitry hack models will be out soon. He didn't elaborate as to when, but was curious if you plan on reviewing a prototype of this new devise?

[RCModelReviews]

Yes, I certainly hope to.

[kneedrag]

Either way I will make sure Bruce gets his hands on one when they are available.

[Flash1940]

Hi folks....especially you....Bruce....

I have been going through all the posts in this thread and I can't seem to find an answer to my problem. I plan to install a DIY kit in my JR-XP652. Before doing all the surgery I have elected to test the system by picking up the modulating signal from the trainer jack and using an external 10.08 V battery to run the kit. In observing the signal (PPM) on my scope The signal has a DC level above ground of 180mV and has an overall amplitude of 1200mV peak - peak(unloaded). It's a 6 channel system and I can see all the pulse widths change when I move the sticks or switch. I'm using a DSC cable I made several years ago....and works just fine.
My DIY kit has the diode mentioned in other posts. The system binds just fine.....but there is NO modulation. NO servo movement. The RX is a known good RX. I even tried a coupling capacitor in series with the diode to no avail. Haven't tried the coupling cap without the diode yet.
Here's my question: Does the negative going signal need to go near system ground....now the signal is nearly1000 mV below ground??? Is a 1200 mV peak - peak signal large enough to modulate the DIY with good solid authority??? If not....then a buffer amp will be needed to increase the level of the modulating signal.
Maybe somebody can help me sort this out....
Thanks....

Flash

[Flash1940]

Upon further testing.....the output impedance of the signal source (trainer jack) isn't low enough or in better terms.....stiff enough to drive the DIY V8HT module. It doesn't pull the 3.286V created by a pull-up resistor on the DIY board down far enough to modulate the system. Without a schematic on this stuff.....everything is an experiment ! Very frustrating for an old country boy with enough electronics background to work on a 5 tube superhet !
I will keep trying things....

Flash

[BlueSkyRoro]

Hi Flash,

I don't have much electronic background, but the first thing which came to my mind was if there might be a problem with the 2 seperate batteries you are using ...I would try and use the build in battery for both (Radio and FRSky TX Module) and therefore have a common ground and + level. Maybe it helps?

I myself did also not want to start drilling holes in my radio before I checked the module I received for operation. But I did not bother too much about
cutting the + / -/ PPM cables inside the radio and using them directly.......I could have soldered them back together (to 35 MHz) if I wanted to....

Roro

[Flash1940]

Thanks Roro, for your response. And as you advised....I did that. I opened the TX and went directly to the board connector. The signal is much stiffer and is inverted from the signal at the trainer connector. So I hooked right into the connector....see the pictures. Same situation....NO modulation of the DIY kit. RX shows steady led indicating bound condition.....but no servo movement. I have another transmitter with a FrSky module.....JR 8103 that works the same RX just fine......so that eliminates the RX as a problem. I am beginning to lose faith in the DIY module.

Inside view of XP 652 TX....sorry....old camera !

TX INSIDE_02_sm.jpg (98.21 KiB) Viewed 19378 times

Scope pattern

SCOPE PATTERN_XP 652_sm.jpg (83.82 KiB) Viewed 19378 times

Flash