another model t question ( feedback )

[sunnslaughterer]

when i put a guitar pickup close to the preamp tubes...my second gen model t makes this crazy feedback...and reacts sort of like a theremin

i sort of like it...but im curious if it is in need of service

its got new(er) preamp tubes installed

any ideas?

[jaywalker]

Congratulations Sunnslaughterer! You have apparently discovered the original "Easter Egg" that resulted from a clandestine meeting between Mr. Theramin and Mr. Sundholm just prior to his (Theramin) being spirited away by the KGB. It's true; the model "T" is in fact the code name for what this wonderful device is: a Theramin (!!!) cleverly disguised as the ultimate tone weapon of the cold-war era. It's a well-known-fact that it was the use of this secret weapon, cranked to 10, that caused The Wall to fall.
 

[JoeArthur]

First of all, you're not supposed to put your pickup close to the preamp tubes!! 

Several things come to mind.  The first is microphonic pickups.  A microphonic pickup will squeal like a pig if brought too close to a speaker - the magnetic fields will interact.  This can also happen if you get too close to the output transformer for the same reason. 

You didn't mention if it just started happening after the tube change or not.  One thing I know for sure is that the Model T doesn't like people that leave the metal shield off it's tubes.  If you didn't put them back on, and it just started happening with the tube change, this is the most likely cause.

[sunnslaughterer]

the feedback/squeel has always occured. not just since the tube change. when i received it, there were no tube shields. any advice on where to find some. thanks, it's greatly appreciated.

[JoeArthur]

http://www.tubesandmore.com/

Look under vacuum tube accessories.