[Heathkit] SB-220 socket question

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Is there a problem with  SB-220 tube sockets?  I found this note in the 
warranty info on the RF Parts web site

"Tube Pin Heating or desoldering resulting from defective sockets (i.e. 
SB220) are not considered a warranty item. We recommend examination of 
original tubes for signs of this problem."


What are the indicators of defective sockets and is it just better to 
routinely replace these 30 yr. old sockets rather than risk the tubes??

Thanks
KA9CCH