[R-390] R-309A T503 differences

[Thomas Hoyer]

The T503 in the 390A I'm working on measures 7 ohms on the primary and 13 ohms on the secondary.


According to the signal tracing levels in the Y2K book, with 10mV into the grid of the 6AK6 I should see the line meter at 0 min. I need to input 13mV to get the line meter to 0. 


Backing up - I ran all of the level tests through the AF module and all meet or exceed the levels shown in the Y2K manual.


Back to T503, the Y2K book calls for 6 ohms on both pri and sec windings. I was able to source two other T503's - all three are constructed differently with different resistor and capacitor combinations. One of the three measures 6 ohms as specified. I installed that one into my IF unit and have the same results. 13mV gives me 0 on the level meter.


I did adjust both pri and sec coils for a peak on the line meter with 13mV at 30% modulation.


Chasing a sensitivity issue and this is the first stage I'm seeing issues.........


Tom
W3TA