Quote:
Originally Posted by jhiesey
On channel 3, both modulators behave the same (weak, smeary color). That means there's definitely an alignment issue in the tuner, right?
The modulator I have isn't a Blonder Tongue; it's a Standard SCM550HP, but it also has an IF loop. Part of the reason I got it was so I could hook the 45.75Mhz IF output directly up to the IF stage of the TV, but I haven't actually tried that yet. I'll do that tonight.
The audio IF oscillation is using a tuner signal. What I observed is that if I tune the IF transformer it goes smoothly from kind of working to oscillating wildly at a bit over 4.5Mhz.
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Yes, must be the tuner, but only on the tuned RF amp stage(s) for the bad channel(s).
Don't know what to say about the oscillation. Maybe use the scope probe as a handy capacitor and poke around looking for a sensitive point that is supposed to be bypassed and quiet but isn't?