I recently got a Magnavox CR-192 FM tuner that had been restored. I did an alignment, but didn't have a way to do the discriminator properly. Took it to work and did the discriminator alignment, but while trying to get it just right I suddenly lost the ability to adjust it right and found when I connected anything to the grid of the mixer tube I got a 10.7 MHz oscillation. I could also connect to a couple other pins and get the same oscillation. Now I did have to fix the discriminator transformer when I got it as one nut holding the trimmer cap had come loose. Had to resolder a wire inside as it had come loose when I removed the transformer cover. I doubt an issue with that transformer could be causing the oscillation. I can remove any if tube or the mixer tube and the oscillation stops. There is one original electrolytic cap still in use which I will replace Monday. Any idea what the problem could be? Here's the schematic http://www.nostalgiaair.org/Resources/327/M0010327.htm I won't be able to do further troubleshooting until Monday. Tuner had worked well, but had some distortion which according to the alignment instructions was to be expected if the discriminator wasn't adjusted properly.