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40-201 Output Xfmr Issues
#10

I decided to add the negative feedback circuit similar to what Philco used in their late 1940 sets. That approach involves adding a 4.7ohm resistor and a 68 ohm resistor in series across the secondary of the audio output transformer. I did not have a 4.7 ohm resistor, but I did have over 100 10 ohm resistors, so I paralleled two of them to make a 5 ohm resistor. I soldered a 68 ohm resistor in series with the 5 ohm resistor across the secondary of the output transformer. I added a terminal strip alongside the transformer to hold these two resistors at their junction. Then I added a yellow wire back to the terminal strip where the black wire from the volume-tone control circuits came from the top of the chassis to a terminal strip underneath. At the same time, I removed the wire that was added that grounded that point. Now the negative feedback will be restored and keep distortion to a minimum as the designers intended.

Joe
   


Messages In This Thread
40-201 Output Xfmr Issues - by Joeztech - 12-14-2013, 05:14 PM
RE: 40-201 Output Xfmr Issues - by morzh - 12-14-2013, 05:24 PM
RE: 40-201 Output Xfmr Issues - by Joeztech - 12-14-2013, 07:08 PM
RE: 40-201 Output Xfmr Issues - by Ron Ramirez - 12-14-2013, 07:20 PM
RE: 40-201 Output Xfmr Issues - by morzh - 12-14-2013, 07:23 PM
RE: 40-201 Output Xfmr Issues - by Ron Ramirez - 12-14-2013, 07:25 PM
RE: 40-201 Output Xfmr Issues - by Joeztech - 12-15-2013, 06:37 AM
RE: 40-201 Output Xfmr Issues - by Mondial - 12-15-2013, 12:55 PM
RE: 40-201 Output Xfmr Issues - by Joeztech - 12-16-2013, 04:03 PM
RE: 40-201 Output Xfmr Issues - by Joeztech - 12-22-2013, 10:49 AM
RE: 40-201 Output Xfmr Issues - by codefox1 - 12-23-2013, 03:03 PM
RE: 40-201 Output Xfmr Issues - by Mondial - 12-23-2013, 04:57 PM
RE: 40-201 Output Xfmr Issues - by Joeztech - 12-24-2013, 07:21 AM
RE: 40-201 Output Xfmr Issues - by Joeztech - 12-24-2013, 08:48 AM
RE: 40-201 Output Xfmr Issues - by Joeztech - 12-24-2013, 04:19 PM
RE: 40-201 Output Xfmr Issues - by Joeztech - 12-24-2013, 07:22 PM
RE: 40-201 Output Xfmr Issues - by Joeztech - 01-08-2014, 07:41 AM
RE: 40-201 Output Xfmr Issues - by codefox1 - 01-08-2014, 08:27 PM



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