Changes in CRTs

[Jeffhs]

I asked this question in at least two different threads, but haven't yet received an answer. Are dark-tint CRTs with aperture grilles and inline electron guns now the industry standard for CRT-based color televisions, or do some very cheaply made Japanese/Korean imports, with manufacturers' names we may never have heard of, still use the old delta-gun tube with a shadow mask? In particular, are there any late-model (1990 to present) Thomson-manufactured RCAs which still are still being made with the old style tube? I realize Sony has used the inline tube in its Trinitron TVs for at least 20 years, and still uses these CRTs in its new Wega sets; I'm just wondering, however, if other manufacturers have jumped on this bandwagon as well. Seems to me the inline tubes produce a much better picture than the original delta-gun tubes did. I would think the inline tubes would also be less trouble from a convergence standpoint.

BTW, where are the convergence adjustments in modern sets? My RCA CTC185A7 doesn't seem to have a conventional convergence board (as I noted when a technician had the back off the set for service a couple years ago). Are the convergence adjustments all in software these days? For that matter, are there any conventional potentiometer controls in today's TVs, or is everything controlled by adjustments in hidden service menus? I think the only standard control on my set is the focus adjustment, and even that is designed to be adjusted with a special hex-head tool. The master G2 adjustment might be directly above or below the focus pot, but I'm not sure. That's probably been incorporated in software as well.

[Chad Hauris]

The last RCA's with delta guns were made in '80 or 81. Most manufacturers quit making these type sets also around that time. No one would make these anymore as the convergence system is more complicated and costly than the inline system.

Almost all of the modern sets do not have any dynamic convergence adjustments...the center and edge convergence are adjusted by positioning the deflection yoke side to side and up and down and also by the permanent magnet adjustments on the crt neck. There are wedges to hold the yoke in place once the convergence is set. Some of GE's inline tubes did have convergence coils and pots back before their consumer line was sold to Thomson, however the convergence adjustments were simplified from the delta gun sets.

[andy]

You won't find any convergence adjustments on a Thomson, or later RCA. RCA for years used a single piece of magnetized plastic around the neck where the center convergence and purity rings would normally be. They either custom magnetized it for the CRT it went to, or had tight enough control over their CRTs to not need any adjustments. Later on, they started literally gluing the deflection yoke to the CRT neck so that once it's setup at the factory no yoke adjustments are possible. The advantage is that the yoke will never work its way out of position, but if the yoke fails you have to replace the CRT.

I have removed yokes from Thomson CRTs to allow me to reuse them in another set, but I had to destroy the yoke to get it off without breaking the CRT.

[bgadow]

The newest delta crt I recall was the 19" Emerson my cousin got in the early/mid-80s. I once had about 4 or 5 used crts for those el cheapo sets, given to me by a local tv repairman. I guess the chassis would die before the tube. I don't know if they were all delta, though.