Bartman
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In the last week I've had to expand my skills to include removing and replacing BL's from an Okto XL board and I've also been pulling and replacing SMD components from the BL's themselves. Here's a brief list of what I've come across.......
The little black resistors that are very near the mounting holes on the tops of the BL's are VERY VERY VERY prone to damage when the plastic nuts are being installed and removed. Be VERY VERY VERY careful when mounting boards or removing them because the resistors crack or get knocked off VERY VERY VERY easily. With a cracked or dislodged resistor you'll get blinking red lights instead of the usual solid red light that indicates the board is ready to go.
There are two groups of pads on the bottoms of the BL's for establishing the address or number of the motor controller in the I2c stream. By putting a solder jumper across the various pads the boards are given their identities (#1, #2, #3, etc). If too much heat is used to place the solder jumpers, the solder holding the other SMD components in the area can melt and allow the components to float off their spots. If they move far enough they won't be in position to participate in the circuitry and the BL will not function. Only use enough heat to get the solder to lay out on the pads and then stop.
With the mounting holes for the capacitors the positive points are both on the inside and the negative points are both on the outsides of the board. the inner positive holes on the XL board (not the BL although the BL holes have the same polarity and position) are hard to solder and require a lot of heat. If you've got a BL with a mystery ailment and you're absolutely sure that the components and I2c jumpers are all correct, try putting a dab of flux around the positive legs of the capacitors on the power board side of the joint and re-melt the solder. Even add a little bit of solder if the underlying pad is visible at all.
All of this is in addition to having the capacitors hot-glued to the BL's. MK and some of the dealers use a small dab of black hot glue that is insufficient for the job of holding the BL's in place. THe black hot glue is hard when dry and has little adhesive power to grip the capacitor body. I've been using clear hot glue from the crafts store and it remains soft and sticky enough to keep the capacitors from coming loose. Of course, all of this hot glue makes a bit of a mess if you ever have to replace a FET but that's a bridge I'd just as soon cross when I get there rather than let the capacitors buzz and break off from vibration.
Regarding the FET's, I've had the pleasure of removing and replacing those as well. There's a great video on youtube that shows the task being done on a first-version BL but the steps are the same. If you're going to try it I'd recommend soldering the body of the FET in place before trying to solder the legs. Place the FET on the board with tweezers then just hold it in place while heating things up. The solder will flow under the FET without much effort although it helps to leave a dab of flux under there to clean things up when you apply heat.
I've got another board to fix so I may have a few more suggestions to add. In order of heat required I'd say the positive legs of the capacitors on the power board side require the most heat and the SMD (surface mounted device) components (resistors, FET's, etc.) require the least. SOmewhere in the middle are the motor wire attachments, I2c jumpers, capacitor leg joints on the BL side of the joint, etc. the blade soldering tip that came with my iron is too big for the SMD components but the pointy tip I've got is too small for the capacitor joints.
Getting intimate with the BL's and the power boards has helped me to become a little more assured of the BL's abilities to do their jobs. I'm seeing problems caused by mechanical damage, heat damage, and poor assembly and each problem helps the "MK is just plain bad" fears to subside a little. It's what I've got so I've got to make it work at this point. Besides, they fly really well!
Good luck,
Bart
The little black resistors that are very near the mounting holes on the tops of the BL's are VERY VERY VERY prone to damage when the plastic nuts are being installed and removed. Be VERY VERY VERY careful when mounting boards or removing them because the resistors crack or get knocked off VERY VERY VERY easily. With a cracked or dislodged resistor you'll get blinking red lights instead of the usual solid red light that indicates the board is ready to go.
There are two groups of pads on the bottoms of the BL's for establishing the address or number of the motor controller in the I2c stream. By putting a solder jumper across the various pads the boards are given their identities (#1, #2, #3, etc). If too much heat is used to place the solder jumpers, the solder holding the other SMD components in the area can melt and allow the components to float off their spots. If they move far enough they won't be in position to participate in the circuitry and the BL will not function. Only use enough heat to get the solder to lay out on the pads and then stop.
With the mounting holes for the capacitors the positive points are both on the inside and the negative points are both on the outsides of the board. the inner positive holes on the XL board (not the BL although the BL holes have the same polarity and position) are hard to solder and require a lot of heat. If you've got a BL with a mystery ailment and you're absolutely sure that the components and I2c jumpers are all correct, try putting a dab of flux around the positive legs of the capacitors on the power board side of the joint and re-melt the solder. Even add a little bit of solder if the underlying pad is visible at all.
All of this is in addition to having the capacitors hot-glued to the BL's. MK and some of the dealers use a small dab of black hot glue that is insufficient for the job of holding the BL's in place. THe black hot glue is hard when dry and has little adhesive power to grip the capacitor body. I've been using clear hot glue from the crafts store and it remains soft and sticky enough to keep the capacitors from coming loose. Of course, all of this hot glue makes a bit of a mess if you ever have to replace a FET but that's a bridge I'd just as soon cross when I get there rather than let the capacitors buzz and break off from vibration.
Regarding the FET's, I've had the pleasure of removing and replacing those as well. There's a great video on youtube that shows the task being done on a first-version BL but the steps are the same. If you're going to try it I'd recommend soldering the body of the FET in place before trying to solder the legs. Place the FET on the board with tweezers then just hold it in place while heating things up. The solder will flow under the FET without much effort although it helps to leave a dab of flux under there to clean things up when you apply heat.
I've got another board to fix so I may have a few more suggestions to add. In order of heat required I'd say the positive legs of the capacitors on the power board side require the most heat and the SMD (surface mounted device) components (resistors, FET's, etc.) require the least. SOmewhere in the middle are the motor wire attachments, I2c jumpers, capacitor leg joints on the BL side of the joint, etc. the blade soldering tip that came with my iron is too big for the SMD components but the pointy tip I've got is too small for the capacitor joints.
Getting intimate with the BL's and the power boards has helped me to become a little more assured of the BL's abilities to do their jobs. I'm seeing problems caused by mechanical damage, heat damage, and poor assembly and each problem helps the "MK is just plain bad" fears to subside a little. It's what I've got so I've got to make it work at this point. Besides, they fly really well!
Good luck,
Bart
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