[Vintage-Audio] Tracking Weight

[Duane Fischer, W8DBF]

In days of old, when cash was Gold, And music came on a disk. When needles
tracked, and static cracked, Then X grams equaled Y risk. 	
	
What was the depth of the groove on the 33 1/3 rpm records? Was the needle
supposed to track at 3 grams for a depth of 1 mil?	
	
And to think, some of us Scotch taped a 4.11 gram Lincoln penny on the tone arm
to prevent skipping!	
	
When did the depth of the grooves decrease and the tracking wight drop to 1 gram
or less? The middle sixties?	
	
thanks.	
	
Duane w8DBF