12au7 in place of 12at7 in tuner

[Carbsandcaps]

I’m up to my eyeballs in 12au7’s. There’s alot of tuners and receivers out there that use 12at7’s in the fm mixer/ oscillators. What happens if I put a 12au7 in place of the 12at7? Yes I’m aware that I can get a 12at7 for $10 but I’m just curious what happens.

 

[gadget73]

the internal capacitance is a fair bit different so expect it to run off frequency. It might function but I doubt it would function overly well.

 

[Buck Rogers]

12AT7 is a High Frequency triode, 12AU7 is not.

Originally designed for TV tuners.

They will usually not work or only work on the low end of the dial.

 

[Tom Bavis]

6DT8 is a good sub for ECC85/6AQ8. 12AZ7 is near exact sub for 12AT7, though it draws more heater current. 12AT7s (and other FM front end tubes) have a hard life - they have to be biased hot to work well at 100 MHz.

 

[gadget73]

yeah I've replaced a number of weak 12AT7 tubes in tuners. Often bad only on one side though.

 

[egellings]

I’m up to my eyeballs in 12au7’s. There’s alot of tuners and receivers out there that use 12at7’s in the fm mixer/ oscillators. What happens if I put a 12au7 in place of the 12at7? Yes I’m aware that I can get a 12at7 for $10 but I’m just curious what happens.

Not recommended if it's used in the tuner's front end.

 

[Mr Boochie]

Just use whatever type that the manufacturer originally used. This is usually the safest path.

 

[peterh]

I’m up to my eyeballs in 12au7’s. There’s alot of tuners and receivers out there that use 12at7’s in the fm mixer/ oscillators. What happens if I put a 12au7 in place of the 12at7? Yes I’m aware that I can get a 12at7 for $10 but I’m just curious what happens.

There is no shortage of 12AT7 tubes NOS or new production.
If You have a surplus of 12AU7 then i suggest you sell some of them to pay for the correct tube.