Model D board maintenance

Not often I remove the boards on my model D (ser.nr. 11966), but I have to change glide potentiometer, and there isn´t much space to do it with the boards in place. So, while I have two boards removed, should I clean the contacts or anything? If so, what should I use to do that?

You can clean the gold “fingers” with a soft swap dipped in 90%+ pure isopropyl alcohol but it’s probably more important to make sure all the fingers still have a firm grip on the boards and are in good alignment. Whenever you open up old gear it’s also always good to remove any debris inside and to fix any loose connections, dangling unconnected wires, and bad solder joints.