04-08-2025, 10:58 PM
The shield is on the 6H6.
It was, in fact, a missing jumper to connect the main chassis ground to the RF chassis ground. Just like that, all of the tubes lit up. But still no sound. I did a complete test of the audio output section, and it works great. The quality of sound reproduction is amazing if I feed a signal into the J200 port used for audio input testing. I then began testing the IF section. I could initially inject a 20mV IF signal into the input of the second IF amplifier, and heard an output tone. I used a 500 Hz signal on a 455 kHz carrier. The next step in the documentation is to input an IF signal into the input of the middle IF can by connecting the generator probe to the plate of the first IF can. I tried that, and immediately heard a loud pop. After that I was unable to get an IF signal to pass through, even if I went back to the first step which worked. I see no signs of damage, but something obviously happened.
I am wondering if I got lucky the first time when I tried feeding a signal into the grid of the second IF can. The documentation says to use a “moderate” level signal. I’m wondering if 20 mV is actually too low.
I can still inject audio to the audio section and hear it through the speaker. So that’s good news.
It was, in fact, a missing jumper to connect the main chassis ground to the RF chassis ground. Just like that, all of the tubes lit up. But still no sound. I did a complete test of the audio output section, and it works great. The quality of sound reproduction is amazing if I feed a signal into the J200 port used for audio input testing. I then began testing the IF section. I could initially inject a 20mV IF signal into the input of the second IF amplifier, and heard an output tone. I used a 500 Hz signal on a 455 kHz carrier. The next step in the documentation is to input an IF signal into the input of the middle IF can by connecting the generator probe to the plate of the first IF can. I tried that, and immediately heard a loud pop. After that I was unable to get an IF signal to pass through, even if I went back to the first step which worked. I see no signs of damage, but something obviously happened.
I am wondering if I got lucky the first time when I tried feeding a signal into the grid of the second IF can. The documentation says to use a “moderate” level signal. I’m wondering if 20 mV is actually too low.
I can still inject audio to the audio section and hear it through the speaker. So that’s good news.
Joseph
Philco 46-480
Philco 49-906