I was biasing my amp, and for some reason both of my 5881 tubes won't get bais close to .038mA. If I bais 1 tube at .038mA the other will read 52. So I tried my new pair of el34 and try to bias them again and the same thing happen 1 will read 38 and the other 1 will read 52 if anyone knows what is wrong plz help me out.