hello everyone!
i am new to this forum and i was hoping to get some help on a little problem i encountered!
i managed to fry a component on the pcb inside my spektrum sm1001 ko-propo module mounted on my ex-10 helios..... and it's so burnt that i cannot identify it
these modules cost a lot and i cannot buy another one or find one on ebay.... so i am looking to replace the burnt component on the pcb with my limited soldering skills!
anyway, if someone out there is still using this obsolete module, i would really appreciate some help, like a photo of the back of the pcb showing clearly the components, unfortunately it's my first post and i cannot attach a picture... this component is a small squared black chip/resistor/fet.... that has 4 legs and is located just under the the hm5 94v-0 writing on the backside of the pcb
thank you in advance guys!
p.s: a photo of the pcb is in my photo album! (thx roelof!)

You can put up a photo in your photo album

thank you sir! i just added the photo in the album "parts"

I do not have the KO version but the Futaba, I will take a look if I can find it. It looks to me a voltage regulator but then the question what went wrong, this looks like reversed voltage or a too high voltage.

yep ! it’s reverse voltage! there is a 3pin socket in the battery compartment meant for a 10s nimh, i plugged a 2 pin jst 3s lipo in it and the module smoked! guess i plugged it in reverse!

i guess it's the low-dropout regulator, now i need to know which one to get (sot223, ams117, lm1117....).
what do you think ?

I did not have the time to look it up, will hopefully check tonight

thx a lot!

It is a capacitor, in this case a tantalum. Basically you can put anything in the place or even nothing, so far I could read the print it is a 10uF/16v



The voltage regulator is located on the other side of the PCB in a large DPAK housing. I could not read it all because it is placed between 2 pcb's but it start with LM293.... probably a 2937 and it shows 3.3 so a 3.3v version. You can measure over the other capacitor if the voltage regulator is still alive.

alrighty then! will check also the LM2937, and i don’t think i can leave the spot where the burnt capacitor was empty like you said because when i plug the module in the ko transmitter and turn it on, the battery voltage reading on the lcd screen starts to act weird showing values erratically around 6v and lower…
anyway, thx a million for your time, i really appreciate!

You need to clean the PCB, it is burned and so carbonized, that can give a shortcut or a low resistance. And the PCB traces are damaged so I think when cleaned you need to repair them.

yep i did, i replaced the capacitor and everything is working fine and dandy!
thx again my friend….
btw do you still use you the spektrum dsm protocol?
i’ve been out of the game for 15 years and i just got back to rc recently so i dusted off my ex-10 and restarted using it(when i bought it in 2007 it was the top of the crop!) i guess it has a sentimental value and i am still not ready to let it go….

i looked up the lm2937es-3.3 datasheet ( check my photo album) and it says that there should be an input capacitor and an output capacitor , the cap that burnt on my pcb was the input capacitor and it should have a capacitance of 0.1 mf , as for the output cap, it should have a 10mf minimum capacitance.
how come the input cap on your pcb is 10 mf ? shouldn't it be 0.1 mf since it also uses the lm2937 ldo?

It is a standard design rule that a regulator need a capacitor on both sides and as close as possible. Basically on the input side it is for a better stabilised voltage and with an LDO to be sure with a low input the voltage drops will not affect the working. On the output the capacitor is to prevent a resonance because the output voltage is also feed back into the regulator. The datasheet tells the default stuff but is not needed to hold on. Most of the time they advise a ceramic 100nF and an electrolytic capacitor of at least 10uF because both have a bit different working and do fill up each other. A tantalum capacitor has a bit of both. Today there are in SMS high capacity ceramic capacitors from 1uF up to even 470uF and are now well used to rule out any type of electrolytic capacitors.

No, I do not use it anymore. I have (still) 2 Futaba T3VCS transmitters and with them 2 Spectrum HRS modules and 9 receivers and a normal DSM module with 3 receivers and the telemetry system. But since 4 years I now use a Futaba T7XC and as a spare a T4GRS.