LDR is an abbreviation for Light Dependent Resistor. These were used in TVs of the '60s-'70s (Magnavox comes to mind, though other sets may have used them as well) to automatically adjust the brightness of the picture under various room lighting conditions. This feature was generally found in high-end Magnavox color sets, such as their fabulous 25" three-way entertainment center (TV, phono, AM-FM radio) of the mid-'60s, and a few standalone console TVs of the same vintage. It could be defeated by a switch if the user wanted to set brightness and/or contrast manually.

Thanks :) My first Zenith had this...it was a menu option I could turn on and off called Light Sentry.

The L.D.R. techonolgy is so old? I thought it was from the '90's.
Anyway, since I've seen the title I knew it was about an really wooooooooooow tv set!

The L.D.R. Technology. is recent Telecolor... you can say ' ...so old .. ' 70's and less lolll ... sure, the 90's compared to 2000's it's different.. ;)

I have two of these, which I purchased this year, one from a thrift and the other from Craigslist. They are both Colortrak 2000's, but different. One is a F27155AK June 1988 Thomson Electronics model with a SCART connector and the rest typically found on the Dimensias(?). It has a pincushion effect. Sound is great with external speakers added.

The other is a FLR2522T October 1985 RCA, which has a purity/convergence problem in the upper right corner(haven't tried to degauss, yet, not sure if that's the problem either). The sound on this unit is really nice, without adding any speakers. I may do that later.

I have read that the pincushion/convergence issue could be a pincushion circuit replacement need(maybe?). Since it rarely but occasionally turns off and comes on again - there are some solder joints that need resoldering, most likely(?).

I enjoy these alot, especially the one with SCART connector. They could both use repair and tune - finding someone in this Atlanta area might be in order, since I am NOT equipped with instruments or the tv repair know-how. Hope you enjoy the photos - everyone's contributions here add to the videokarma.org value. Thank you.

The tvs's are at : https://www.flickr.com/photos/41385747@N02/sets

That '85 is especially nice in my opinion.

The both sets use bonded yokes. The yokes are glued on the CRT
& the convergence / purity rings are often unadjustable.
Purity problems are from:
Unglued yoke.
Trim magnet fell off, they are usually V shaped on RCA.
Something magnetic near by.
If a big magnet got near the auto degauss may not fix it,
manual degauss it.
Degauss circuit not working.
Bad CRT, shadow mask moved.
Its best NOT to touch the neck rings. They wont need adjusting unless
it was messed with.

The most common pin problems with RCA of that vintage were
open caps or the pin diode. Also had a few pin out transistors fail.

BTW with RCA use the chassis number. Its on the tag and or
in the set. Starts CTC###.

73 Zeno:smoke:

Jon A. - I felt the same, as the sound and looks are cool looking. Thank you.

Zeno - I hope it was something magnetic nearby. The man who sold me this tv last month said his sons used it profusely for gaming. At the time I was buying it, I noticed the problem, but dismissed it as something that a degaussing ring would cure. But your list is a great reminder to me and others who are looking at tv repair solutions, that there are sometimes many reasons for problems. Thank you so much for taking time to list those. I can certainly do a degauss and will, once I get a degaussing ring. I would like to look inside this 1988 set to find the chassis number and I'll do the same with the other, and make notes. I know from reading videokarma.org that these RCA's are referred to by chassis numbers C140's, so I do need to find those numbers. Thank you for the list, again, and I can do some visual checking, of course, and if I have success with the degauss, I'll be shouting.."yay".