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Broke key guide on 6sn7 how to keep using tube

I broke off the key guide on a black glass Sylvania vt-231 and a black glass RCA while using a Garage 1217 tube adapter. The key hole is very tight on these adapters and so are the pin sockets. I know the tube is still good just don't know how to orient the pins withe correct socket holes. If I can figure this out I can just use a paint pen on tube and socket for the future. There are no numbers in the bottom of the tubes so where do I go from here? I have more of these tubes but hate to throw in a junk drawer. Thanks for any help.
paulcreed
elliottbnewcombjr
5,108 posts
 
I've done this.

With strong light, magnifying glass, careful look by young eyes, see where the positioning tab was broken off the tube center post. Scratch a vertical line in the tube base where the tab was. Line up the scratch with the key slot in the tube socket, insert.

The whole center post snapped off? Still have the piece? Figure out where the tab would be if the broken piece was re-attached, scratch the outside of the base like above. 
imhififan's avatar
imhififan
2,108 posts
 
You can use a keyway replacement from Tube Depot,

https://www.tubedepot.com/products/octal-tube-keyway-replacement

The filament pins of 6sn7 are 7 and 8, you can use a DMM ( digital multimeter ) to identify the filament pins by using ohm meter, other pins will show open circuit except pin 7 and pin 8 have resistance reading.

https://i.pinimg.com/originals/d7/c6/e4/d7c6e4adc921afe65ab6af7ebeec279e.png

paulcreed OP
533 posts
 
Thanks imhifan, got it, put meter on pins and found 7 and 8 and key is located between 1 and 8. Your awesome thanks for the info, you saved some sweet old vt-231 tubes.
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