Bad solder on ESC/RX-crazy servo behaviou

[flydiver]

Just discovered my 2nd problem with cracked solder joints on the ESC/RX box. This is evidenced by one servo (generally) that exhibits strange behavior. It may seem to be OK on bench testing but on flight that channel makes the plane fly erratically. A new flier will swear they are a victim of 27mHZ glitching and immediately go out an buy a Spectrum something-or-another. It's OK-it's a good excuse-you'll need it in the future anyway since 27mHz is a dead end. ;D

The solder joint where the servo socket connects to the PCB board cracks (back underside). Those little buggers fit in there really tight (thanks PZ) and it only takes a few removal cycles to flex and crack the joint.

The 'resting' joint (unstressed bench test) may work fine but under flying stress and vibration the joint opens and closes and that servo goes nuts. Elevator is particularity bad, so that's the one that seems to go.

You can see the crack under STRONG magnification or reproduce it by wiggling the base of the wire while it's powered. A good joint won't do anything when you move the wire base-a bad one makes the servo jump all over. If the servo jumps around that's likely the problem.

Don't confuse this with a bad/worn POT on a servo or servo binding. A worn POT will jitter a little but not react to moving the wire. A servo that is binding will settle right down if you remove the control link and won't move either if you jiggle the wire.
A bad joint makes erratic large jumps and quits when you stop messing with the wire or giving control inputs.

Replace the ESC/RX or re-solder. I've re-soldered both now with a VERY fine tipped iron and strong magnification. Just baaarrrreeellly touch it to re-melt the solder with an extremely small blob of new solder to add. If you solder adjacent poles together I think you probably blew it. Same if you slop the solder on.

Once confirmed as fixed again epoxy the hell out of the solder joint and servo socket. DON'T get epoxy in the opening or you've ruined all your work.

fly

[admiralev]

hey fly i took a look at my old servos and realized that was my problem! it took a magnifying glass to get the complete picture. wish i would've known that earlier...o well

[flydiver]

Swore it was a glitch and went right out and bought a Spectrum - didn't you?
Took me 2 days to figure it out the first time-a very frustrating and scary 2 days. Plane would test OK on the ground, take off, then go up or down at random. Crazy making.

fly

[admiralev]

the specktrum was still something i would've ended up getting anyways, so it doenst really bug me

[flydiver]

Completely good. The 27mHz stuff is a dead end. Need to get out of it sometime. I've just noticed that there is actually a whole lot less glitching than people claim. Maybe I'm fortunate where I fly but I'm had very little, most of that with low end RX's.
Now, I have a buddy that has a LOT at the same field. It doesn't seem to matter what RX he uses. I think maybe his TX could be off frequency a bit or something.

Addendum - my buddy turned out to have a bad TX crystal in his Futaba. He got a JR7202 and all his problems went away. Months later he replaced the Futaba crystal (same frequency) and now that one works OK.

fly

[admiralev]

if he's flying 72 he should have a look at the crystal and possibly swap it out for a new one or a different frequency

[flydiver]

He's done a bunch of RX swapping along with different Xtals. The only thing left is the TX Xtal or TX itself. He's had RX's fail on him to the point of crashing. I've put my Xtal in them and flown them for months without issue. The only thing that seems to work are Bergs or DC Coronas.

How do you validate the function of a TX? Only way I know is to send it in.

fly

[admiralev]

o honestly i have no idea. i was in my hobbyshop once when a guy came in with TX problems and they took a look at it, swapped the crystal and then took it out in the parking lot to test it and he was fine.

[duck9191]

hey at least yours had solder lol, the rx for one of my nitro trucks (sportwerks) only had 2 of the 5 wires for the steering servo soldered to the board, rest were untinned pads and tinned wire.

[airphotoky]

Blows a huge sigh of relief

I thought I as was going crazy. At first I thought it was interference. Then I thought it was my new battery. Then, I was just thinking it was a short of some kind in the wiring. Now I know. Thank you so much for sharing the information you posted here. I have a new replacement cub on the way because I thought it was something wrong with mine. Now I can fix my old one and I will have two!

Here is a link to my original description of my problem.

supercubclub.proboards.com/index.cgi?board=crash&action=display&thread=2580