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Senior Member
Username: pace

Post Number: 973
Registered: 4-2004
Posted on Wednesday, January 01, 2014 - 3:58 pm:   Edit Post

Ok, I'm trying to swap out tubes as it seems that the gain on each channel is different from the other.... BUT.... How do I remove these two piece shields to get at the tubes??!?
Advanced Member
Username: smuprof

Post Number: 216
Registered: 12-2003
Posted on Wednesday, January 01, 2014 - 5:46 pm:   Edit Post

I'm not sure about the "2 piece" part, but most of them are a canister with a spring in the top to keep the tube seated. To remove, just push down on the top (i.e. push the canister toward the front of the F2B) and twist. The canister is held in place by the spring pressure pushing against a notch in the canister. When you push down and twist, you free the canister/shield from the notch and the spring will help push the shield off. Once you put the new tubes in, just reverse the process.
Advanced Member
Username: xlrogue6

Post Number: 280
Registered: 8-2002
Posted on Friday, January 03, 2014 - 9:55 am:   Edit Post

The upper part slides down inside the lower part. This can be problematic if tubes with the slightly larger glass envelope have been installed. Those shields were designed for old American and western European tubes, which used a slightly smaller envelope than the ones found on some current production tubes. If the top won't slide down try a very small amount of liquid lubricant applied at the top, give it a few minutes to work its way down.
Senior Member
Username: gtrguy

Post Number: 668
Registered: 9-2004
Posted on Friday, January 03, 2014 - 2:20 pm:   Edit Post

JJ tubes work well here and I think Alembic uses them, if I remember right. Many 12AX7 tubes do not fit the shield.
Senior Member
Username: pace

Post Number: 974
Registered: 4-2004
Posted on Saturday, January 04, 2014 - 6:26 am:   Edit Post

Thanks guys, I figured it out only minutes after posting the question, and I posted a thanks Thursday, but I guess that didn't go through…

So anyways, THANKS!!….

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