01-16-2022, 12:22 PM
There a a few things to try. First connect your signal generator output to the grid cap of the 24A IF amp tube and see if you can receive the signal. This will eliminate the possibility of a problem in the first IF transformer blocking signal from the 1st detector tube.
Try tuning your signal generator above and below 175 KC while listening for output. Perhaps the IF is way out of tune which is why you are not hearing anything at 175 KC.
Removing the cap wire from the 1st detector tube and feeding signal through a 0.1 uF cap sometimes may present a problem. With no DC path to the control grid, there is no bias on the tube and it may assume any random plus or minus voltage depending on grid emission or gas content. I usually leave the cap wire on and force signal to the grid across the input tuned circuit. If the tube is operating properly, you should get IF signal through easily enough.
This is assuming that the !st detector and IF amp tubes have the proper cathode, screen grid and plate voltages applied and have been confirmed correct.
Mike, WA2YGA
Try tuning your signal generator above and below 175 KC while listening for output. Perhaps the IF is way out of tune which is why you are not hearing anything at 175 KC.
Removing the cap wire from the 1st detector tube and feeding signal through a 0.1 uF cap sometimes may present a problem. With no DC path to the control grid, there is no bias on the tube and it may assume any random plus or minus voltage depending on grid emission or gas content. I usually leave the cap wire on and force signal to the grid across the input tuned circuit. If the tube is operating properly, you should get IF signal through easily enough.
This is assuming that the !st detector and IF amp tubes have the proper cathode, screen grid and plate voltages applied and have been confirmed correct.
Mike, WA2YGA
