AMI B tube question

wingnut049 · by **wingnut049** » Tue Oct 09, 2012 9:56 pm

I have the black amp in the B that has the tubes marked. I replaced the 6L6's and the sound improved. I replaced the 5U4 with no difference. The amp is also marked for 2 6N7 tubes. I bought one set from Russia and 1 set of NOS locally. Neither of them work altough the tubes from Russia were each missing a post (hope that's the correct word). I'm not buying any more tubes until I find out why the replacement tubes don't work. HELP!

by **Ron Rich** » Wed Oct 10, 2012 6:52 pm

What kind of a "post" ?? I would guess, it was not deemed necessary ??
Ron Rich

wingnut049 · by **wingnut049** » Thu Oct 11, 2012 4:39 pm

The amp has the following tubes printed on the amp: 6L6 (2), 5U4 (1), 6N7 (2). The service manual agrees with the 6L6 and 5U4 but it states that the other two tubes should be 6SL6GT (1) and 6SJ7 (1). I do know that the two sets of 6N7's that I bought don't work. It was suggested that the motor mounts might be bad but I don't see any motor mounts. Hindsight being 20/20 maybe there aren't any and that's why I have the hum. Any advice, short of selling the B, is greatly appreciated.

by **Ron Rich** » Thu Oct 11, 2012 5:31 pm

Well, it's kind of confusing---
You will first need to determine if you have the correct amp. model installed in your juke. After which, you will will need to determine exactly which tubes go where in the amp. ( I would be inclined to think it is a different model amp, and go by the tube marking that you see on the amp.). If you are not able to do this, you will need to contact someone that is familiar with amps. of that age and have him work on it. As for the rubber motor mounts--there are three posts holding the motor in place, and all three should have a rubber grommet on each one. I don't remember what type they used on that model, but I ASSUME it is the same as AMi used in later models. Ron Rich

wingnut049 · by **wingnut049** » Sun Oct 21, 2012 7:23 pm

Hi Ron - Thanks to Bill Bickers and a little careful reading on my part I've realized that the B has an amp that belongs in a D. In addition I've misread the tube number (twice - the problem with getting older) and ordered 6N7 instead of 6SN& which is the correct tube. According to Bill there had to have been modifications made for the B to accept the DD amplifier. Obviously these mods were made. In all fairness to Freddy Bailey I believe this amp was in the jukebox when he acquired it. Needless to say I've ordered the proper tubes and we'll see what happens.