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Electrosil69
Electrical
- Jan 20, 2013
- 2
thread240-221138
I worked for Electrosil from 1969 to 1971 and remember the TR type resistors. They were glass "cane" coated with tin oxide. A "thread" like that on a bolt was cut into them to create the resistance value and then they were covered in paint. The final coat of paint was the resistor code BBROYGBVGW. The resistance value was determined by the pitch of the cut thread. The TR numbers were the physical size of the resistor body. I think I still have a tin of the in my garage! I hope this helps original poster awood.
I worked for Electrosil from 1969 to 1971 and remember the TR type resistors. They were glass "cane" coated with tin oxide. A "thread" like that on a bolt was cut into them to create the resistance value and then they were covered in paint. The final coat of paint was the resistor code BBROYGBVGW. The resistance value was determined by the pitch of the cut thread. The TR numbers were the physical size of the resistor body. I think I still have a tin of the in my garage! I hope this helps original poster awood.