Quote:
Originally Posted by miniman82
You say it works 'reasonably well' right now, what exactly is keeping you from giving it the ole siskel and ebert?
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Well, I suspect it would benefit from a video IF alignment, but I'm not equipped for that, so the question is how well it can perform without realignment. (Or, if you know anyone within a 3-hour drive of Seattle who would like to align a Dumont RA-102, please send me that info.)
In light of that, here are the remaining issues:
1. Weak audio. Sounds OK if you crank it, but you shouldn't need to turn volume halfway up before hearing anything. When I injected audio on the RA-102, it was strong like my RA-103. (Yes, I did tweak the audio adjusters to get best (under the circs) volume & fidelity at the "best video" tuning point.)
2. The tuning is twitchier (narrower?) than my RA-103, and the tuning meter is pretty unresponsive. The needle does move a bit while you tune, but way less than I'd expect. Again, if bad alignment equals weak signal, I guess these symptoms aren't surprising. (I have cleaned the devil out of the tuner, its tube sockets, etc., and both tested and tried subbing all of those tubes.)
3. Vertical jitter. There is still a
slight jitter, even after I replaced a vertical xfmr and most other vertical components. Not noticeable when watching ordinary program content, but visible if you display something like a cable TV program guide with lots of horizontal lines. Dumont published a service note with a modification to reduce jitter; I have read that, but not tried the mod.
4. The picture blooms and loses focus if you have set the contrast/brightness to correctly display ordinary content, and then the station displays a very bright scene, like a white ad screen with small dark lettering. Poor HV regulation? In the course of getting the HV to work at all, I replaced nearly every related component on the p-s chassis.
Quote:
Originally Posted by miniman82
I ask because there's a good chance that what's keeping it from being outstanding now will likely still keep it from performing it's best later
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True, problems usually don't cure themselves. I'd be happy with this set if I only improved 1, 3, and 4 in the above list. If I
could inject video, that might help to evaluate these issues. For example, is the jitter present when injecting video vs. receiving signal through the antenna? And so on.
Regards,
Phil Nelson