I got a very nice condition Triplett 630-PL Type 5 from estate sales for $25. Everything works well except the 10VAC and 3VAC range don't work well. I found because the rotary switch doesn't make good contact at those positions. At first the 2 positions didn't work at all but after I spray some deoxit in the switch it works but sometimes I still have to move the switch back and forth a bit to get it to work. I wonder how to clean the switch better? Can it be taken apart? How tough is it to do so?