could you wait for today I'll ask a shop near my house for this IC.

Found some more information

http://diydrones.com/profiles/blogs/3-50-repair-frsky-diy-dht-module-after-reverse-polarity-mistake

http://il.farnell.com/texas-instruments/tps54331d/buck-3-5-28v-3a-570khz-8soic/dp/1645383

Farnell and digikey have a high shipping cost. If youre not plannig visiting the store you might be better off getting the diy kit from hk and replace the entire module.

Oh ok.. I discussed issue with few SME and they said ideally i should get the VR locally... Did you got chance to check in local market?

Yups, probably you missed my update earlier. They only have LT117 which is not a drop in replacement

Thank you Girish.

do you think its safe to put new module on this tx?

Should i perform any check before putting new module on this TX?

At the onset I doubt there will be a problem, besides that the FrSky might not even power up if a vr inside the Tx has also gone kaput!

So things surely will help if everything is found in order before hooking up the new kit. Do check the voltage that's coming out of the tx and if you can, do check the PPM signal as well. You can check the PPM signal by using a normal audio cable, plug it in the microphone port of your pc, and the trainer port on the other side. Download something like winscope, you should be able to see the PPM signal on your computer. If the PPM, +ve and gnd are in order, all should be well.

Quoteplug it in the microphone port of your pc, and the trainer port on the other side

Sorry, not the trainer port but the ppm pin and gnd, outer shield of audio cable will go to gnd

Wow that is great idea. Thank you.

So now i have 2 things to do...

1) check output of all VRs

2) Check the PPM signal

If all ok then install new module

Thank you,
Atul

Applications of TPS 54331 are :

Consumer Applications such as Set-Top Boxes, CPE Equipment, LCD Displays, Peripherals, and Battery Chargers
Industrial and Car Audio Power Supplies
5V, 12V and 24V Distributed Power Systems

My side project is searching TPS 54331

Spot on. All the best  

One more thing you need to check for...Beer in the fridge or scotch in the bottle...might come in handy when you can't find which solder join ain't working...


If you find some 54331, lemme know, I may barter it with some Scotch

Deal Done sir 

Some of my colleagues visit US frequently. I will try to source from there.

I appreciate your support and guidance.

Thank you,
Atul

Hi All,

I recently burnt my Turnigy 9x transmitter by connecting the battrey with reverse polarity, After switching on within seconds I got smoke and burnt smell from the transmitter. Later I noticed my device has been burnt due to reverse polarity.

I referred many forum and many of them had hit with this problem and the solution was to replaced Voltage regulator(VR), SMD capacitor and 2 more componenet. I replaced all the below listed componenet referring the link

http://openrcforums.com/wiki/index.php/Reverse_Polarity_Brick_-_Fix

1. 78L05 in SOT-89 package in the mainboard
2. replaced with 22uf 25v capacitor in the mainboard
3. 78L05 in TO-92 package in the switch PCB

I have not replaced "78M05 in TO-220 package in the RF module".

During the tranmitter burnt, I was hit with another problem, were my "Rhino 2620mAh 3S LIPO" got bad. One of the cell had gone bad, Now my output from the battery is only 7.24v. When I test my transmitter after replacing the component(with the 2 Cell LIPO), The 78L05 VR input in the mainboard  gets 7.24v but the output is only 0.32v instead of expected to 5.0v. This is unique where none has reports. I have tried replacing 2 nos 78L05 VR in the main board but still the same.

I have attached the photo with input/output marked. Please someone guide me to resolve the problem.

surprisingly, polarity protection is easiest thing to do. I wonder why they do have it: http://www.instructables.com/id/Reverse-polarity-protection-for-your-circuit-with/

There are circuits with 0v drop, but this is simple.

Girish another one for you...... seeing so many cases of wrong polarity I am planning to make and sell a connector for all.....

Please someone guide to resolve....

http://www.rcindia.org/radios-and-receivers/burn-turnigy-9x-transmitter/msg161861/#msg161861

Send him PM --- girishsarwal  ..... he will help you out.

I would recommend you to plug sim cable and see of your TX is working fine.
If yes then replace the VRs in order and after every replacement check the voltage.

girishsarwal is SME on this and he can definitely give you some good advise 

Sorry Purush, I was really caught up with so many things over the past two days...

Glad to hear, Purush has been able to fix his radio by replacing the VR....Sorry Purush, I could not help you in time...

GS

PS: While I've had quite some success in modding and fixing many of these, I am certainly not an SME on 9xs or electronics for that matter...Another hobbyist with a knack to open up things ... Happy flying!

Saurabh sir, banao banao, mere liye bhi ek (actually chaar paanch)...

Finally I was able to fix my transmitter, It looks like the replaced 78L05 VR on the mainboard was also a faulty VR, I replaced third VR and fix all the problem and got beep sound and display....

Some time back I mail you regarding the reverse polarity with my turnigy TX and I was able to fix after replacing the below parts including the RF module.

1. 78L05 in SOT-89 package in the mainboard
2. replaced with 22uf 25v capacitor in the mainboard
3. 78L05 in TO-92 package in the switch PCB
4.  "78M05 in TO-220 package in the RF module".

Now the issue is, when I connect my lipo will full charged, the display show in 10.7v instead of 12.1v. I confirmed with multimeter the lipo has 12.1v. when the display comes to 7.6v after some usage, the TX start to beeps...., at the time if I check with multimeter is only 10v. what is the reason behind.