Philco FM1000 very strange circuit experts needed
Ok, here it goes. I am currently working on a 1948 Philco AM/FM/SWL set, and have all the filter caps replaced, a lot of the paper caps replaced, all tubes tested, etc. I have also followed the chaotic alignment procedure as well which is very different than typical alignment instructions from sets of this day. (worked on MANY MANY SWL sets including zenith, hallicrafters, collins) On FM though it uses a tube called an FM1000 for the discriminator, and in FM mode it "motorboats" although when tuning the dial it will pull in stations which can be barely heard very faintly in the background way below the noise level of the motorboating. For the life of me, I have checked all voltages, and signal levels, and cannot figure it out. Also, the FM circuit is very different from what I am used to. Is anyone familiar with this problem, or an expert on the older Philco FM designs?
What is the model number?
The Philco Single-Stage F-M Detector. There has recently appeared an F-M receiver which utilizes a locked-in oscillator in a manner somewhat similar to the Beers receiver. However, due to the nature of the feedback between the mixer section of the unit, and the oscillator, no discriminator is required. Instead, the audio output is obtainable directly from the plate-current variations of the mixer tube.