skal1
Well-known member
yes the input xfmr for the control amp, i am using DMM to measure voltage at the xfmr
regards
skal
regards
skal
OK, so, apparently it lacks some gain but it shouldn't be a problem really.skal1 said:yes the input xfmr for the control amp, i am using DMM to measure voltage at the xfmr
regards
skal
It was a long while ago, but I took the values from the published curves (input and output levels) and put them in an excel table with the amp gain levels etc.what method did you use to create the Fairchild control amp gain structure chart.
Maybe your B+ is not correct. hwo far are you from 3.6? You should know that voltages in most tube gear are +/-10%skal1 said:well i am still struggling with this project, i feel like giving up :'( , but i will not, anyway enough of my emotional state .
So i am looking at the control amp again , i have strip it back to just the 12ax stage , and the dc threshold pot , my ? are
1)why can i not get the 3.6Vdc at the cathode's of 12ax like on the fairchild schematic without trimming the 18k cathode resistor
Vacuum tubes 101b: dispersion of characteristics for tubes in the same batch is +/-10% at best, +/20% in different batches, +100/-50% from different manufacturers2) why is that when you exchange the 12ax with another one the cathode voltage changes from the 3.6Vdc
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