[Mondial]

Eric, I was just doing the alignment on my 48-482 today, so maybe I can give a little guidance. You need to input an IF signal at exactly 9.1 MHz at a low level, just enough that it can be heard. You place a jumper wire between the plate of the FM1000 and the 47K load resistor, effectively shorting out the secondary winding of the FM detector transformer. Then carefully adjust the trimmer capacitor (not the slug) until you hear a squeal. You then need to turn the trimmer back and forth until you find the silent spot in the center of the squeals. This is the zero beat. The frequency of the squeal will decrease as you approach zero beat, if you continue to turn the trimmer it will increase again. Use the minimum signal which will still produce the sound for the most accurate adjustment.

The procedure then says to remove the jumper and then adjust the detector transformer slug to achieve zero beat again. Here I was unable to get a real zero beat, rather I adjusted the slug for best audio with a FM modulated signal. Perhaps you will have better luck. Finally I got out my sweep generator and adjusted the slug for the most linear slope on the detection curve, which was a pretty critical adjustment.

After this alignment the FM reception sounded great and the stations tuned in without distortion, which was not possible previously. The FM 1000 detector can perform really well, but the alignment is very critical.

Here is a link to an explanation of how the FM 1000 detector works, with drawings of the response curves obtained with proper and improper alignment.

http://www.philcorepairbench.com/tube/fm1000.htm

Let me know how you make out!