BK 9920, fixable ?

Hey all. I got a BK 9920 off fleabay a while back. It took a bit of work but I finally got it running. The wires for the servo plug were all bare where it connects to the ESC, and the orange wire was nearly pulled off the esc. Not just the wire, but the contact patch. There was also a resistor busted off the back of it. I resoldered the wires to the ESC, and replaced the missing resistor. It worked great for a week or two, and finally the orange wire gave up and pulled off the ESC taking the rest of the solder tab with it. I can't seem to locate the trace that the solder pad made contact to.

Anyone have enough experience working on the 9920 to determine where I could solder the orange wire to ? Is the ESC just shot ? I can put up a pic tonight if it would help.


J.

Nobody probably knows.

If anyone has a bk 9920 and a multimeter, let me know! If you could find a spot on the PCB that has continuity to the original solder pad that is missing from mine, I could possibly solder the wire in a new location. there isn't any of the pad left on mine for me to check, and the trace does not appear to be visible from the surface.

[BrianG]

If the trace doesn't seem to go anywhere, there is probably a tiny hole near that patch. This electrically connects the traces on both sides of the board. If you can't solder to a nearby trace, you might have to pull the boards apart for closer investigation and get to the other side of the PCB. Once you do get it fixed, I would put a bead of hotglue or something on the wires to the PCB to act like a sort of strain-relief for those small wires.

sweet, I found the trace, and it's in good shape. I scraped off enough of PCB to get good contact with it. I'll try tonight to get a wire soldered to the end of the trace, and see what happens.

J.

success!!

The trace actually went left from the pad very close behind the caps. I guess I had just overlooked it before. About 1/4" of it was pulled up from the PCB, but still connected. Since it didn't reach where the solder pad was anymore I guess it was easy to overlook, all tucked up behind the first cap like it was.

Anyhoo, the little bit that was pulled up off of the PCB was perfect to tin and solder a wire to. It made for a very secure connection, which I then glued down to the PCB. I'll use some hot glue or rubber cement to secure all three of the wires so they don't get strained so badly in the future.

Thanks for the encouragement Brian!!

/me is happy

J.

[BrianG]

Congrats!

[Toyman]

Good job, I broke the little jumper pins off the circuit board that are used to program the transmitter, I ended up with a jumper wire soldered to the little spots that were left visible. Man talk about stressed out, but i got it done.

Kind of a bad design with the contact points all at the edges and so fragile. After what I'd read on the 9920, I was hesitant to buy it. I'd heard a lot about cogging issues, and terrible customer service. I'm really impressed with the performance of it though. The acceleration is incredible, with very little cogging at low speeds, and the brake/reverse strength is spot on. Runs nice and cool compared to both my MM and 125B as well. Besides, I picked it up used and damaged for $75. Not much to loose on a good ESC. I'm ecstatic.

I think I'll pick up one of those HXT hybrid motors and pair it up with the 125b in the e-revo, run the bk and 8xl in my e-savage, and then I have the MM and 5700 in my Tamiya DF-03. Plenty of fun to go 'round. My poor models that are still on brushed setups never get used, lol.

J.

[Toyman]

Ya I agree, I really like the 9920 with 7XL and 8XL in my maxx on 14 cells, wish I could find a couple more of them. Steve