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My last ditch trick is to alternate spraying the tube with Trifluoroethane and PB Blaster. A cheap source of Trifluoroethane or Difluoroethane is just getting a can of Liquid Air or Dust-Off used for blowing out dust from electrical parts. Just hold the can upside down and spray to freeze/chill the tube. There is also CRC Freeze Off but it does not get as cold.
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