| Electronics > Repair |
| removal of 7-segment displays from PTH board |
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| unseenninja:
Yeah, I don't even see a ground plane to make life harder. De-soldering something like that display is easy! Just give each pin some new fresh solder and then de-solder them. It will work fine with a good quality tool like your Pace. Don't forget to wiggle the Pace a little as you suck up the solder. All that's needed afterwards, if there is any sticking, is to just grab each pin with some fine nosed pliers and give them a wiggle. That will separate the pin from the side of the plated trough hole and when you wiggle the last stuck pin, the display will simply fall out. When you solder in the new displays, do better than the last person and clean the flux off properly afterwards. |
| BurningTantalum:
Thanks, UnseenNinja. I have had the Pace for decades so am quite familiar with component removal, but was worried as I suspected the holes in the pcb would be very tight on the pins. Experience is that one, two or three pins are relatively easy to keep heated with a single wide chisel tip and remove the component but multiple pins are more difficult, but if the pin is tight in the hole there is no chance of clearance around the pin even if the solder is removed with vac. The faulty control and display board is back in the equipment for now until I modify the brightness of the displays on the spare board before installing it. I didn't want any more display failures as they are not cheap. I think the displays are from Kingbright (LSD582AEGR-20 dual common anode Red/Yellow) but can only find SBA56-21EGWA Red/Green. Not at all important as I am swapping all of them. I intended to reduce the 16v supply to the anodes via two red/yellow drive switches (3-transistor flip flops driven from the Atmega,) to lower the drive current to segments but due to the pcb layout it is very difficult to isolate that supply. I will have a try but may have to resign myself to changing the 57 1206 1k resistors hence the Talon query in 'Repairs'. Thanks all, BT |
| unseenninja:
If the pins are really tight and you can't clear the solder, the best alternative is some nice thick copper wire. Wrap it around the pins, flood everything with solder. The wire distributes the heat to all pins and you can get the solder liquid on every pin all at the same time. Good luck with isolating that 16V supply. I really wouldn't enjoy having to replace all those SMD resistors. |
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