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Well, I think I gave this thing my best shot. If anyone out there is considering buying a Ramsey TV-6C, I'd be inclined to say, "Don't waste your money".
The source of the major problems seems to center around Q5, the 2N3866 output transistor. The power-supply is a rock-solid regulated 9V with no ripple whatsoever, which is great. The audio and video amplifiers do their job perfectly, and the two are mixed appropriately, which is also great. The local oscillator, tuneable to channels 3-5, puts out a very nice sine wave at the proper frequency of choice (mine being 62-ish MHz, or channel 3), which is great too. 90% of the "squirreliness" appears to be at the output stage. The Q5 transistor is a brass button type, presumably for shielding and heat dissipation. It does neither well. The collecter is connected to the case, but in this circuit the emitter is grounded, so the case is free to collect stray radiation and rebroadcast it in something of a feedback situation. It also runs uncomfortably hot, and its characteristics change with temperature, which leads to drifting and inconsistent performance. On no video/audio input, it also doesn't reproduce the oscillator's sine wave all that well (ramps up faster than it ramps down, a "wiggle" halfway down). This leads to harmonics, such that when tuned to channel 3, channel 8 also has the signal, almost as strong. And there's a mess on channels 2 and 4 and even 5, so there's no hope of buying several units and broadcasting all your favorites on more than one frequency.
If you moisten a finger and place it on top of Q5 (and let the pain subside as you bring its temperature down), then tune the various trimmers for best picture, you get a very stable situation. Take your finger off and all hell breaks loose. Obviously a guy can't use it that way. Applying your finger does two things, it sinks all the heat, and it damps out all the transients floating around the transistor's case. There's an immediate catastrophe when you remove your finger, which worsens over the 60 seconds that the transistor takes to heat back up. Replacing your finger removes the worst of it, then after 10 or 20 seconds, as the temperature subsides, you get back to "tuned". Pretty unacceptable.
I tried cold-water-pipe grounding the case, no improvement. Couldn't think of much else to try there, outside of digging up a cadaver and permanently mounting its finger to Q5.
I removed the onboard antenna and soldered a 25-foot piece of 75-ohm coax in its place, then placed the (removed) antenna at the other end of the coax, across the basement, and tuned the trimmers to that configuration (after Q5 heatup). This actually improved things almost to the point of satisfaction. I guess operating Q5 an inch away from the antenna is the TV6C's biggest flaw, and perhaps the reason for an external-antenna jack on back.
However there's one other flaw, I can't trace down nor explain, in that there's a slight, sudden increase in amplitude at the antenna, then a slight decrease, at a specific period (60 Hz?) that results in a series of lighter vs. darker blocks of picture, about half the picture height each, which slowly "walk" up the picture as you're watching your program. It's noticeable-to-annoying, and no amount of tuning removes it completely. Like I said, the regulated 9V is rock solid, but I don't know, maybe the regulator is radiating something?
It's also disturbing that the video and sound are both xmitted at the tuned frequency (they should be separated by 4-5 Mhz). They seem to count on "bleed" to get both to the TV set. I'm guessing that's why it's so hard to get clean sound AND clean picture at the same time, although rather easy to get one or the other.
So that said, I'm s__tcanning the project. The guys at Ramsey didn't do their homework.
Save your money. Not worth the price of admission.
-k
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