Restoring HP-65

[albertofenini]

Dear All, it's nice to be back again.
I had posted several years ago, then due to personal reasons I had to stop working on our collection.
I also have a new helper, now that my son has turned 11, he has joined me in this passion.
I will post later pictures of our collection.
We are now in the process of restoring three HP-65, trying to get at least one working unit out of the pieces.
We also have noted that although all the calcs had been stored away cleaned and sealed, some of them have developed oxidation when not corrosion, even if none of them was stored with batteries inserted.
I think it was mostly due to non perfect cleaning of the original corrosion.
Before posting I have searched in this and in the old forum, looking for a good recipe to obtain the removal of oxidation, of the corroded parts and to make shine again the contatcs or the soldering joints.
I remember using a dilution of vinegar with water and baking soda but I can't remember the exact composition.
Can anyone please help us ? Take a lok at the green thin lines close to the gold traces.

Thanks in advance to everyone for your support !
Alberto and the young collector Edoardo !