Bryan many thanks great images...they tell all, "the rude Gemini"hahaha Imgur does this just to cover their legal ass .? Its like a bug has got in and done its thing all around the bottom of the board.? Really needs a good clean bottom half.
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U6 pin 8, "the black pin" goes to R44 and is "R1in" which is Pin 3 of J7.??? Pin 4 of of J7 is "T1out" from U6 pin 13.?? I think its just been marked with a black permanent marker to identify.?? But there is a lot of detritus and dirt on the PCB...use a and cleaner spray (electronic or Isopropyl 70%/Distilled water 30% mix)?
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Clean the board replace that socket.?? Cut away old as much of the socket as you can with side cutters.?? Don't worry...its going, so don't be nice about it.?? Leave the pins sticking up? though.?? Then heat these pads to melt (with solder iron), pull pins out, one at a time (with pliers, tweezers).? If any solder is left, clear holes with soder wick dipped in flux or rub flux on it....it sucks solder up much more quickly when heated with an iron.?? Ensure iron tip is clean and a little solder on it to start the process of "wetting" sucking up the old solder.?? If any solder "is still left" in holes...small hand drill and 0.7mm drill out.?? Clean up as above with flux cleaner or Isopropyl 70%/Distilled water 30% mix and brush.
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Seat new socket "fully so tabs go thru PCB"...solder in...use flux!?? Then with an air heat gun (or what ever you have) ....heat those little black tabs underneath and once they soften, stick a small screwdriver blade in between "its slit" and press or force this slit apart till it cools.?? This helps the tabs grip the PCB better so it won't move!??
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Oh the bottom part near the PWR sockets and fuse F1...looks a little like corrosion on bottom half F1 and maybe around the base of the board...just check...if so get back I can help how to clean fix.?? F1 check it...looks dull on bottom upper pad.?? Just sayin, if it works, leave it.?? Lastly the motor sockets are wearing around the top plastic.?? Be careful plugging in Plugs as twisting trying to find the location lug, tears at the plastic.?? I do have "new sockets".....but not many (6) and these are not available anywhere, and i mean anywhere, unless you want to buy them by 10,000 lots.??
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Lastly the RV1/2/3/4 are looking slightly "been hot".?? They are to protect the the encoder lines.?? They are varistors and can go bad.?? FTM, if its running ok...leave them.? But if you get any runaway drive or drive issues...take them off or replace them. ?? V5.5MLA0805L.? Frankly I usually take them off (if they short out they can damage motor encoders) , but as said if you don't have any drive issues...leave them
Anyway...lets see how you go....the board isn't in bad condition just looks like some critter been using it as a play area around the Serial port and socket!?? Thanks for great images...they really help
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Cheers
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Get back if any help needed, only happy to do so
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Brendan
