Here it is, a 1950 Emerson 7" TV model 639 resurrection/restoration attempt. It was an eBay find, not cheap but I thought very unique. I hope I can get this finished before I "retire"
It looks to be in very good condition visually and has almost all original tubes. It is series strung using mostly a mix of octals and 7 pin tubes. It uses a 7JP4 picture tube which is electrostatic deflection. It looks largley unmolested, and seeing almost all original tubes, may be a low hour set. It could also have failed the picture tube or something that put it out of service. I need to test the big tube and hope it isn't shorted or has an open cathode or heater. It's full of leaky paper caps and some bumble bees but isn't a recappers dream. It kinds resembles a large radio with a picture tube. I kinda liked it because it is a little different than what I have seen around. So far I have found an open fuse/resistor off the selenium rectifier. I bypassed and am beginning a slow power up using a dim bulb to see of the caps will reform or anything shorts. Here a few pics of the project so far:
If I could find the place called "Somewhere", I could find "Anything"
Tim
Jesus cried out and said, "Whoever believes in me , believes not in me but in him who sent me" John 12:44
Hello, TV MAN. Is this TV superheterodyne or direct amplification? Which company is the manufacturer of this kinescope? How many reception channels is this TV tuner designed for and what is the frequency range? These three questions are of great interest to me, because I have two Soviet-made TVs of 1948 and 1952, and I will be very interested in comparing their circuitry, assembly and used components.
I'm going to check and see of I have the Sams on it today. I found a date code of August 12 1949 stamped on the tuner. It has Emerson written on the picture tube base, but I'm sure RCA or someone else made it.
If I could find the place called "Somewhere", I could find "Anything"
Tim
Jesus cried out and said, "Whoever believes in me , believes not in me but in him who sent me" John 12:44
(This post was last modified: 03-27-2023, 11:19 AM by TV MAN.)
It looks very much to be along the same lines as one of the Motorola VT-71 style sets, though Emerson probably put their own spin on it, like only using a single selenium rectifier rather then two. The 6 KV caps in the vertical circuit will all have to go before it will do much. I think Bob Andersen may have one of these but hasn't done a restoration on it yet, he is working on one of the earlier ones with the five 25Z6 tubes and a transformer. These basically use a scope tube with a white phosphor rather then a green one, I think the largest electrostatic sets use an 8 or 9'' tube, I've heard of 10'' ones but have never seen an example, not even in a book, after a certain point the resolution hits a limit I think.
Regards
Arran
(This post was last modified: 03-27-2023, 01:54 PM by Arran.)
Peter;
I don't know if they ever manufactured a television, in the U.S or Canada, that used "direct" TRF amplification, outside of maybe some of the very early mechanical TVs. As for frequencies used that was pretty much set down for the post war period, some early postwar sets had a channel 1, the rest had tuners with channels 2 through 13, none were fix tuned like the British TVs, and it stayed that way until sets with built in convertors cam out in the late 1970s. I can't give you the frequencies used for these channels, but they were all VHF, and the info is posted pretty much everywhere.
Regards
Arran
Thank you Arran. I asked this because the first mass TV in the USSR was TV KVN49, which was direct amplification, not superheterodyne. It had a small screen with a diagonal of 18 cm, 16 radio lamps and could receive only three TV channels. And I think that his kinescope was developed in RCA
This TV, KVN, was in my aunt's parents' room, and they were watching it all the way into end of 70s, when they died.
It had a water-filled magnifying glass in front of the CRT, and so the pictuire was of a decent size.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Mike, Peter;
Was the KVN49 the receiver that looked somewhat like an RCA 621TS, but with a fabric covered front panel? Did it have electrostatic or electromagnetic deflection?
P.S I looked up the KVN-49, yes it is the one very similar in layout to an RCA 621-TS, not as stylish but I would not turn one away either. Curious how many articles I saw commenting on the magnifier, seemed to use that as evidence of the Soviet Union being technologically behind, though screen size was irrelevant to the technology of the set. Having a TRF front end probably says more, but then again these were built to a price, not unlike a Motorola VT-71 series TV of the late 40s, or the Emerson that started this thread.
(This post was last modified: 03-28-2023, 01:04 AM by Arran.)
Arran, KVN had an electromagnetic deviation. The visible part of the screen was rectangular, but the kinescope itself was round, measuring 7 inches. The magnifying glass was not included in the set of the TV and was sold separately, and there were quite a few options for such glasses from different manufacturers.
In the middle, the KVN is very different from the RCA 621-TS, I don't see anything in common, but ... it seems that the kinescope in the KVN is a copy of the RCA, they are very similar.
I had a rare opportunity to stay inside this evening so I headed to the radio room and decided to see if there was any life in this 1949 Emerson TV. I connected the tube filaments to full 120v and the B+ through a diode off my variac. I brought it up slowly and I could get a little light on the screen (1st pic). On the 2nd attempt I could only get a vertical line. I was quite surprised I had a full 5000 volts on the high voltage, some sync but in the 2nd picture I can clearly see the horizontal died. I'm sure the output caps are leaky or shorted. I do have sound (I can buzz it from the detector cap) but no static or signs of it passing a signal from the tuner. I had to add a couple filter caps to get my power up enough, the originals are dead) but I think this is stunning for a 74 year old TV do do this with very little help! I'll get some parts ordered and see if I can bring this old set back to full life!
If I could find the place called "Somewhere", I could find "Anything"
Tim
Jesus cried out and said, "Whoever believes in me , believes not in me but in him who sent me" John 12:44
