Thanks to you both crtrue and Steven. I want to ask the wider group if you can spare your time to help.
I found time yesterday night to do a second cleaning with isopropyl. The end result is the same, i.e., the phone works: calling, messaging, youtube, etc. Two things I want to check which I observed in the course of the cleaning:
(1) I checked the battery with a digital multimeter. With the setting on DC and placing the negative point of the multimeter on the top end of the li-polimer terminal and the positive end at the lower end of the terminal, the voltage shown is 4.09 volts. When I switch the ends (positive to top, and negative to bottom), the reading is never in volts, always goes to microvolts (mv). Does that give any indication that the battery is defective, and needs to be replaced?
(2) In the Samsung Galaxy A10, there are two tiny wires (not the black strip and yellow strip both of which nicely snap into place) which run from the bottom to the top and they don’t properly snap into the sockets both at the top ends in the motherboard and the lower ends in the bottom chip panel. During this second opening and cleaning, I found them quite loose, and when they appeared to be just in place I placed the top cover plate and the small bottom cover plate very carefully and screwed them. Do you think that these wire-ends not being - and therefore any short circuiting - could be the problem? Does this need a professional to do it? Or is there a right way to gently put them in place? The Youtube videos I checked don’t have such open wires to contend with.
I am undertaking this out of interest to revive the A10, and want to be prepared to deal with any issue that might happen in the future with the costly Samsung A8 that I am now using. There is no guarantee that the structure and connections of the A8 will be similar to the A10 to easily apply any knowledge and tips presently gained. Yet, I want to be in touch with experts and diy-ers like me.
Thanks in advance to those who have something to offer from your expertise and/or attempts.