Show us your vintage B&W sets!

Hey msepic, just an update on my 1950 Admiral's resurrection. It's fixed and working and provides better resolution than you might expect from an early set. The only annoying thing is that it can't compensate for the different types of video that it has to process, like a live local newscast compared to an old film. The newscast will be in such high contrast that a lot of stuff just looks black, but change the channel to an old movie and the picture will be so washed out and lacking contrast that the re-trace lines are always there. It's a case of constantly adjusting which was pretty much what I remember with my family's first TV set in the early 50's. I've read that there are fixes for the re-trace lines (Admiral actually put out a service bulletin for it) but the set doesn't get enough use to warrant taking it back to the guy who fixed it just for that. This TV is in a guest room with old furniture but I knew if I didn't make it convenient to use that I'd get protests from my other half. Found a cable box to make it remote but it got fried after the first round of viewing. I'm wondering if it was cable company sabotage. Haven't found another to replace it so am using a VCR and have put the TV on an extension cord with an in-line switch by the bed since the VCR doesn't have a switched outlet. I just keep the volume at a medium level. Two things I've come to realize about a 10-inch round or "double D" screen: 1) It's pretty small for viewing from more than several feet away, and 2) anything that would appear in the corners of a rectangular screen is cut off--really only noticeable when there is verbiage on the screen or with those little "bugs" all the networks superimpose in the lower right corner. But it's a novelty to watch and after it's been on a while that familiar old smell of warmed up bakelite fills the room. I think you'll have fun with your set once you find the time to get it working.

[andy]

...

Thanks Andy. If I need to take the set back to the fix-it guy I will ask him about installing the circuit you've described. I know I've seen mention of an Admiral document that provides instructions on how to do this so it shouldn't be a big deal. Right now it's more trouble than it's worth to pull the chassis just for this one issue but it's nice to know it's not a major undertaking to fix when and if the time comes for some other repair.

[cork]

HI Andy,

Maybe you have some more ideas on the DC restoration in old sets. All the stuff I grew up with, with the exceptiion of Color sutff, had no DC restoration. I assumed they thought they were saving money, or that maybe they thought people didn't like blacked-out scenes. But then when you go back a little further in time, a lot of the really old (1949 and back) sets did have DC restoration, and either RF HV or flyback HV. Because they had DC restoration they didn't need any H or V retrace blanking ckts. But the problem they did have was raster blooming, since they had no HV regulators. Thus on bright scenes the raster would enlarge due to the falling anode voltage. No DC resoration took care of this problem since the average scene illumination was alway the same, and thus the anode current was a constant after the video coupling capacitors settled from scene to scene. But it was necessary to add retrace blanking since the picture black level was all over the place. I am guess this is the reasoning that went on with the mfr's. What do you think?

[Whirled One]

Originally Posted by andy

The contrast problem you're describing is caused by a lack of DC restoration on the video. Basically, the video is AC coupled, so all the DC information in the video is lost. The circuit needed to restore the DC level is actually very simple, but it was usually not included to cut costs.

The problem might be lack of DC restoration, but I would also suspect a lack of video AGC (Automatic Gain Control) on that set. Many/most TVs from that era either had no AGC, or a less-functional form sometimes referred to as "simplified" AGC. [I'm not sure when improved, "keyed", AGC was introduced.] The result is that the contrast level will change as the signal level changes (i.e. as you switch channels or adjust the antenna). If your set does have at least some form of AGC, there should be an adjustment for it on the back of the set somewhere; that might help a little bit, but don't expect it to be perfect.

In any case, if the problem is poor/no AGC, then you'll see the contrast change dramatically if you adjust the antenna or move it around.

An easy way to tell if a TV doesn't have DC restoration is to see what happens during fade-ins/fade-outs between scenes in a show, or any program material that has large areas of solid black or solid white with some other motion (for instance, a white credit scroll/crawl on a black background). If fade-outs fade to a mid-grey instead of black, or white-on-black titles end up looking like white-on-grey (with the background grey level constantly changing as the amount of white text on the screen changes), or black segments between commercials turn grey instead, then you don't have DC restoration. Most TVs made in the mid-50's through the early/mid-60's don't have DC restoration, but a lot of older sets did.

BTW, regarding that GE UHF converter calibrated in MHz rather than channel numbers: I actually have one of those too, and I don't know why GE decided to calibrated the dial like that either. Then again, the FCC way-back-when actually assigned "channel numbers" for all the assignable frequencies on the FM broadcast band (didn't the numbers start with 200..?), but I don't think very many FM radios ever actually had those channel numbers marked on the dial. Did any FM radio stations ever actually announce their channel number duing station IDs rather than their broadcast frequency?

Andy, thanks for all the great info on DC restoration. There's a 1951 Capehart model 325F over at my parents' place that has been retired since 1962 except for a brief period around 1970 when I had the picture tube replaced, but it needed more than that, as everbody looked like a conehead on it, and this was a good 5 years before NBC Saturday Night came up with the concept! I recently checked the owners manual for it and it does have AGC so now I'm tempted to get this one recapped. Trouble is, I have no place to put it. It also needs the on/off and channel knobs so I will need to find exact replacements for those before bothering to have any chassis work done. Thanks again for sharing all of your knowledge with us on this subject.

[sean]

Here is a set that I used to have. This is a 1951 Zenith H2250R 12" porthole. The set was a basket case when I bought it. I have a webpage up showing the restoration: http://www.angelfire.com/electronic2...R/porthole.htm
I ended up selling it when I bought a 1950 G2350. You can browse around my page and find another page on the restoration of that set.

[Big Dave]

I finally bought a real digital camera. Here is a screen shot of my Philco 50T1403. I need to experiment with lighting and such. But I finally got a useable screen shot...

[Jeffhs]

Originally Posted by Whirled One

BTW, regarding that GE UHF converter calibrated in MHz rather than channel numbers: I actually have one of those too, and I don't know why GE decided to calibrated the dial like that either. Then again, the FCC way-back-when actually assigned "channel numbers" for all the assignable frequencies on the FM broadcast band (didn't the numbers start with 200..?), but I don't think very many FM radios ever actually had those channel numbers marked on the dial. Did any FM radio stations ever actually announce their channel number duing station IDs rather than their broadcast frequency?

I can't speak for other stations elsewhere in the country, but I do seem to remember a station in Cleveland that used to announce both its frequency in MHz and the FM channel number at the top of each hour, during the FCC-required station ID. This was an NBC-owned and operated station (WKYC-FM); it used this particular automated station ID at the top and bottom of every hour ("This is WKYC-FM, 105.7 megahertz, channel 289, Cleveland, Ohio"), when the network's own programming would pause for commercials and local affiliates' identifications. Also, another Cleveland station would announce both when signing off for the night (this was in the '60s-'70s, when FM and some AM stations would go off the air for maintenance late Sunday nights or early Monday mornings).

Yes, the FM broadcast band began with channel 201, IIRC, and ended with 300, 201 being 88.1 MHz and 300 being 107.9 MHz.

There were some very early American FM radios which had the FM channel numbers listed below the frequencies in MHz; in fact, there were even a few very old FM receivers which had their dials calibrated only in channel numbers. Some European FM sets, like Grundigs and others, marked their dials in frequency and channel numbers for years, until everything went digital.

[John Folsom]

As this is the Early B&W and Projection TV forum, here is my RCA TLS-86 "Television Receiver / Projector System" Circa. 1948. This unit was adapted from the RCA model 648PTk, according to the RCA Instruction Booklet. The unit is designed to project up to a 6'X8' image. The photos show the unit operating with a NOS 5TP4 CRT. Sorry, I did not have the unit quite focused properly when taking the photo.

[Eric H]

Originally Posted by John Folsom

As this is the Early B&W and Projection TV forum, here is my RCA TLS-86 "Television Receiver / Projector System" Circa. 1948.

There's one of these sitting in a local Junque Shop. It's been on display in the window for several years now, I've given up on them ever selling it.

I was looking for more info on the Web about this set and found this interesting item:

http://www.terramedia.co.uk/cinema-t...levision_2.htm

[ChuckA]

Originally Posted by Eric H

There's one of these sitting in a local Junque Shop. It's been on display in the window for several years now, I've given up on them ever selling it.

Eric,

You need to throw more money at them.


Chuck

[Marlin Mackley]

Hey guys, the base of that thing is the base for the RCA record cutting lathe. Guess it made sense as transcription records were being phased out and I bet they had a bunch of them around the factory.
Marlin

[Chad Hauris]

Originally Posted by Eric H

There's one of these sitting in a local Junque Shop. It's been on display in the window for several years now, I've given up on them ever selling it.

Just wait around a little while...sooner or later the shop will most likely close down or at least be hurting for money and will give you a fair deal to make some cash. I have seen things sit around shops for YEARS, like 5 years or more, and when it's been there that long, the shop will usually come to their senses that YOU are the only real hope of making any money on the item, and will deal with you.

That projector is awesome, I bet it eats CRTs for lunch ! Modern units are rated 10k hours so with 40's technology I wonder what that one gets, 5k ? Whats the HV on it ? You can probably check for broken bones with its xray output heh. I didn't know anybody had a working one, I saw some original photos of one on a TV site a few days ago.

Now you just need to get 2 more, some color filters and a demodulator for the worlds largest color projector