Originally Posted by bobfa
I messed up big time last night. My Negative wire broke connection on the receiver board. Instead of prying the board off the foam pad, I was lazy and mistakenly soldered from board side to the leg of a tiny diode(??) that is adjacent to the negative connection post. (looks like one of these) .The receiver still binds up, but when you plug in power the tail motor runs immediately wide open. I am pretty sure I fried from heat this little square diode(??). Does anyone have any idea about what and where to order a replacement diode(??). After looking at the price of replacement receivers ($80
) , I went to Banggood and purchased a new V2 for $119 (bgxmas coupon). I have allot of Genius spares, and still would like to try and repair this Genius for backup and try to keep the V2 nice. Maybe I can select a diode out of one of my many non-working V911 boards. Are these diodes pretty generic for 1 cell boards?
If you're talking about the brown device mounted near the positive and negative battery wires then that is a capacitor. Those can be tricky to replace because often they have no markings indicating their value. The one on my board doesn't have any markings.
It's probably a power filter capacitor but I can't really see what it's connected to. Looks most probably connected across the motor(s) power which helps smooth the power and prevent spikes from feeding back into the electronics (brushed motors are especially noisy electrically).
These SMD capacitors are actually pretty tough and resistant to heat but I don't know how much you actually applied. If you just bridged the black wire to the left side (in the picture above) then it should be OK to leave as it is because that side is already connected to the black wire. If you bridged the other side, crossed sides, or burned up the capacitor then you might have an issue.
First try to make sure nothing is bridged to anything else it's not suppose to, fixing those issues may fix it. That capacitor is actually pretty big and relatively easy to access compared to most things so it would actually be easy to replace with the proper tools and skill. You need a very fine solder tip and preferably a temperature controlled soldering iron. SMT devices can be difficult to buy because often you have to buy dozens or even hundreds at a time. I don't know what country you're in but Digikey, Mouser, newark.com, futurlec.com, etc carry these types of things. I usually pull mine off old electronics.
In this situation what I would do is first make sure nothing else is bridged or desoldered because that is the most likely problem. Then try to test across the capacitor looking for a short. Then if no short I would try to measure the capacitance on the off chance I can get a reading. I just tried measuring mine but the positive side has some sort of tough goop on it and I couldn't get a reading (readings with it in-circuit are usually wrong anyway). After that would be removing it for testing. We can only guess at the value, it could be anything but it looks relatively large. However, if it really is a filter capacitor for the motors then the value is not super critical, I would err on the larger side since that looks like a big cap. SMT devices have a package size that says how big they are physically, that one looks like a 1206 (3216 metric) or bigger 1210 (3225 metric) ceramic capacitor. Note that physical size is separate from the capacitor's value.