Dumont RA113 "Burlingame" restoration

[bandersen]

Originally Posted by HighHopes

Bob,

I never worked on a double IF strip set. I hope the engineer who came up with the single strip got a good raise that year. Did you try turning those two adjustments on the top of the tuner?

-Steve
(old fart)

Some of the early, low end sets used a single strip like the Motorola VT-71. I'm pretty sure most used dual IF so they could use amplifiers best suited for wideband AM (video) and narrowband FM (sound).

No, I didn't touch the tuner.

Originally Posted by HighHopes

Bob,

In "Admiral 24C16 restoration part 5 (we have sound!)" at 3:30, you adjust a coil on the tuner which fixes the audio problem. Specifically, it adjusts the output IF frequency of the audio band to properly go through the audio IF stage which you just aligned. You do not re-adjust the fine tuning of the station and presumably the video remains clear (the video IF strip still gets what it needs from the tuner output, frequency-wise).

How can this be without two mixers in the tuner? See my previous post about two mixers.

Steve

I wasn't as knowledgeable about Admiral tuners back then. I'm pretty sure that was the oscillator trimmer capacitor. So all I was doing was shifting the LO frequency a bit - same as adjusting the fine tuning. The passband of the tuner is huge (over 5MHz) with the video and audio carriers being 4.5MHz apart.