#31
|
||||
|
||||
"BTW those two 12K resistors in parallel is how it was originally built and shown on the schematic. Two 12K, 1W in parallel
I'm thinking 5.6K or 6.8K wasn't close enough?" Can you post the circuit? If the original resistors were 10% or 20% tolerance, there wouldn't be much advantage in using two for a nominal intermediate value. More likely they had 1 watt components available cheaper than small quantities of 2 watt - but that could depend on the particular circuit. |
#32
|
||||
|
||||
#33
|
||||
|
||||
Series dropping resistor for screen grids and DC restorer B plus - no reason for precision that I can see. I note there is only one 2 watt resistor in the bill of materials - cathode bias for the horizontal output. There are a few higher wattage wire-wounds, but all the other composition resistors are 1/2 watt or 1 watt.
The peculiar thing is that there is only 1/6 watt dissipated in each of those two 1-watt resistors (see Fig. 41). Maybe this was to keep a low temperature rise and prevent the value from drifting - I'm thinking the actual DC restorer B plus is not critical because brightness control setting takes care of it; unless it drifts, requiring readjustment of brightness. You could test this theory by connecting/disconnecting a 100k or so resistor across these two and see if the black level changes. See Fig. 30, where it appears to be so. |
#34
|
||||
|
||||
Another thought - I wonder how well the DC restoration tracks with line voltage changes.
|
#35
|
|||
|
|||
Another Interesting fun fact, Philo Farnsworth (the man behind the Capehart and Farnsworth Radio and TV Company) actually was a pioneer in early TV manufacturing and had many patents in TV development which RCA ripped off from him, and when Philo tried to sue RCA for patent infringment they took him for a ride and drove him into bankruptcy.
So the majority of those Patent Nos. refrenced to on the back of these TVs that are claimed by RCA are actually Farnsworth Patents NOT RCA Patents. |
Audiokarma |
#36
|
||||
|
||||
Quote:
Popularly attributed to David Sarnoff/RCA.
__________________
Goodness comes from getting the basics right, glory is to be found in tending to the details. |
#37
|
||||
|
||||
Quote:
Capehart was a separate company known for luxury phonograph and Jukebox equipment. Their turnover changer that started as a a jukebox mechanism became the standard for premium home audio both in the high end consoles Capehart sold (which with add on remotes and amps became whole home radio and music systems) and paired with other high-end radios like E. H. Scott. The 2 companies later merged since Capehart wanted into emerging Television Tech and Farnsworth needed the backing of a financially solid company to deal with RCAs nonsense.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#38
|
||||
|
||||
You guys have the timeline and facts a bit off. Philo goes back much further. He filed his patents in the 20s and had his battle with RCA in the 30s. He won in 1938 with RCA agreeing to pay royalties.
Then the war broke out and production was halted. Unfortunately for Philco, by the time the war was over and TV resumed, his patent had expired. Farnsworth Television and Radio Corp was based in Fort Wayne and operated from 1938 to 1951. It was bought out by ITT in '51. Farnsworth bought Capehart in 1938 using the money he won from RCA. Last edited by bandersen; 04-07-2023 at 09:54 AM. |
#39
|
||||
|
||||
Legend has it the RCA lawyer was crying when he was signing the settlement papers. Probably because he knew Sarnoff was pissed.
How many times did someone take on RCA and win? |
#40
|
|||
|
|||
Quote:
hence why RCA was considered a dirty operator for many years was because they basically held a monopoly over the patents for many various electronics technologies including ones that weren't originally theirs to begin with, which is why if you look up some of the patent numbers on the back of many old RCA and RCA Clone/licensed TVs you'll see that they are actually patents originally assigned to Philo Farnsworth and then in small print under the original patent assignee is the words "reassigned to RCA". |
Audiokarma |
#41
|
||||
|
||||
Quote:
on the picture. Even today they make really good pictures in bright sunlight, for example, in a camera made by a guy in Japan using a solid state preamp. In broad daylight even my WWII bomber camera make quite OK pictures. |
#42
|
||||
|
||||
Quote:
|
#43
|
||||
|
||||
old_tv_nut: well, yes, what you say is important for the history.
But the important thing is being first to get a great idea, get it to work even a little, and then get it to market. For example, the Plumbicon works great, but it was an incremental idea. And it was the trailing edge. Comb filters were great, but trailing edge. Digital was a great idea for great pictures. But its big deal is allowing stuffing 8 channels of utter crap into the space on one, not quality for that one. |
#44
|
||||
|
||||
#45
|
||||
|
||||
The contrast control in this set is really odd. They feed the output of the detector from the back of the set to the front through coax, use a potentiometer to vary the level, and run another coax line back to the video amp.
That's what the tube is running down the middle. Wouldn't it be much easier to just vary the bias/gain on the amp? |
Audiokarma |
|
|