RCA Dimensia 26" TV help!

[RCADIMENSIA]

Would anyone have suggestions or contacts to find replacement parts for a 1985 RCA Dimensia FLC2601T set?

I guess it it is a Color Track 2000 internally with the Dimensia control board added to create this particular model. It is the CTC131 chassis I believe.

The set is currently at a repair shop in Minneapolis, MN and the technician is having a very difficult time finding any parts. He believes it is repairable and let me know that the parts are probably available but it will take time and some luck to find them.

I collect CED's have a near perfect set of 1st generation Dimensia components that go with the tv set. Would like to keep it in working order as long as possible.

Any leads or advice would be great. Looking to keep this piece of RCA history alive a bit longer.

[zeno]

Post the 6 digit part numbers & the whole chassis ##.
You may find it here. If not someone will pipe in with any
distributors with OEM NOS parts.

Most of these got bad connections & bad electrolytic inside
the tuner assy. Also bad main filter cans & a few flybacks.
Not much else, they were a damn good set & looked nice on the outside.

good luck
73 Zeno
LFOD !

[RCADIMENSIA]

Thanks for the heads up! Could you by chance recommend someone who may have these older parts? I called the shop that has the TV and he asked if I could provide any information to him or a contact. Any ideas? Thanks for the quick response.

[Jeffhs]

Originally Posted by zeno

Post the 6 digit part numbers & the whole chassis ##.
You may find it here. If not someone will pipe in with any
distributors with OEM NOS parts.

Most of these got bad connections & bad electrolytic inside
the tuner assy. Also bad main filter cans & a few flybacks.
Not much else, they were a damn good set & looked nice on the outside.

good luck
73 Zeno
LFOD !

These may have been good TVs, but RCA could have done a better job choosing a name for them. After all, the name "Dimensia" is too darn close to "dementia", the latter being the medical term for a certain type of mental disorder. I am very surprised the Dimensia line of televisions sold as well as they did (if they actually did sell that well), with a name like that.

[init4fun]

Originally Posted by Jeffhs

These may have been good TVs, but RCA could have done a better job choosing a name for them. After all, the name "Dimensia" is too darn close to "dementia", the latter being the medical term for a certain type of mental disorder. I am very surprised the Dimensia line of televisions sold as well as they did (if they actually did sell that well), with a name like that.

"Takes one to know one" ..........

[Electronic M]

Originally Posted by init4fun

"Takes one to know one" ..........

[Doug]

As previously mention post part numbers someone in the group may have them.
Otherwise
Moyer electronic's
Talon electronic
Parts-link
Ralph electronics

[rcaman]

need to know what part you are looking for. i have some rca parts and jeff yes Dimensia did sell very well.

[Jeffhs]

Originally Posted by rcaman

need to know what part you are looking for. i have some rca parts and jeff yes Dimensia did sell very well.

I did not mean to imply RCA Dimensia televisions did not sell well, or were "bad" sets. These were probably very good TVs; in fact, from what you said, they must have sold extremely well despite the name. I am not that familiar with the RCA Dimensia series of televisions, which is why, after I finish this post, I will look up more information on these sets. From what you said, this particular series must have been excellent in its day, maybe one of the best 25" color TVs RCA ever made in the 1980s, before today's HDTV.

As I said earlier, RCA, being a pioneer in electronic television, made very good b&w and, later, NTSC color TVs. My family's first television, in fact, was a 1954 RCA Victor console; it served us well until we replaced it with a Crosley Super V 21" set the following year. We would have kept and used the Crosley set for years afterward (it worked quite well for many years, with its original CRT; the only problem that set had, IIRC, was a vertical-hold potentiometer with a bad spot) were it not for my mother all but insisting on a new, all-channel TV in the mid-'60s, a year or so before she passed away. We replaced the Crosley set with a new Sears Silvertone 17" all-channel portable.

We put the Crosley Super V TV in the basement, along side the RCA 21" set; both TVs remained there until the early 1970s, until my dad married his second wife in 1972 and my grandmother moved into our house (long story and OT).

When my grandmother moved in, all the old junk in the basement, including the 1954 RCA console TV and the blond Crosley 21-inch set, had to go. Just as well, I guess, since the RCA set, while it worked very well from the time it was new, had developed some problems which rendered it unusable by the time we replaced it with the Crosley TV.

[zenith2134]

Having owned a number of RCA Dimensia 25 inchers, I think they were a fine set of their era. That being said, the previous gen with the CTC-121 chassis (Lyceum) had a better pic on it to my eyes. I once read that those used proper I-Q color demod like an early color set would use.

My last remaining 26" RCA is not as sharp as it once was but, in its defense, it was used when I got it and has never had the back off. It's the MTS stereo model with OSD from 1987.

[old_tv_nut]

Originally Posted by zenith2134

... That being said, the previous gen with the CTC-121 chassis (Lyceum) had a better pic on it to my eyes. I once read that those used proper I-Q color demod like an early color set would use.

Here's some discussion:
http://www.videokarma.org/archive/in...p/t-35530.html
http://www.videokarma.org/archive/in.../t-247011.html

If I can find the long post of mine about the RCA chassis with an IC I/Q demod and its shortcomings, I'll post a link to that too.

[old_tv_nut]

Here's what I posted, about 80% down the page, and repeated here verbatim.

http://www.videokarma.org/archive/in...p/t-23924.html

"That Dimensia IQ demod design was ingenious in that they found a way to make an I channel delay line with only one IC pin (plus one external transistor). As an analog IC designer, I thought that was one of the neatest tricks I ever saw. Essentially, they tied the input of the delay line to ground, then drove the delay line output and what would normally be the delay line ground up and down with the input "I" baseband voltage. They then used the same driving pin to sense the output current!

Despite my admiration for the IC design, When I tested one of those sets for chroma resolution (working at Zenith), it was essentially no better than the R-Y/B-Y sets. The I channel high frequencies were quite attenuated. It appeared that there was too much phase distortion in the IF to allow the I channel high frequencies to be boosted to a useful level. I went through some effort to design a better IF for a possible wideband design myself, but concluded that the NTSC got away with their system design partly because tests were done on small screens. My basic conclusion was that NTSC needed a more symmetrical Q filter in the transmitter - it should have traps on the upper and lower edge that match the 4.5 MHz sound trap (+/- 900 kHz from the chroma carrier). If the Q sidebands transmitted would be sharply curtailed beyond +/- 500 kHz, there could be no quadrature crosstalk from Q into I, and it would behave like the NTSC intended - but NTSC Q filter specs were too broad, and any reasonable IF would show quadrature distortion and therefore the I response could not be boosted to the theoretical value. I proved this by modifying the filters in an NTSC encoder -and when we saw how well it worked, we gave up trying to design an I/Q set, since there was no way to go back and modify every encoder out there."

[zenith2134]

Great information,thanks! A fascinating level of engineering went into color, as we all know.

The takeaway for me is that if the old NTSC standard was the limiting factor, then why did RCA attempt this; and how come in the 80s? Surely, modifying the IF stage on all new sets was out of the question, no?

I'm in the minority who actually prefers proper color rendition over all else. I mean, I don't even think standard definition television was all that bad, since I watch zero sports and never watch a screen size bigger than 27".

Having seen proper Conrac broadcast phosphors being fed from a live camera, nothing can top that at home. I have attempted to compile a bunch of analog studio-grade video gear for at home use. The limiting factor is always the source material.

[old_tv_nut]

The problem was not solvable by modifying the receiver IF, only by modifying the Q channel filter in the encoder. If the Q channel bandwidth would be more sharply limited to 500 kHz, there would be no lower Q sidebands (symmetrical to the 4.5 MHz sound trap) to produce quadrature crosstalk.

The encoder Q filter circuit originally published by RCA had some phase correction for better transient response. It's possible that the coupling could also have introduced a sharper high frequency rolloff than the NTSC spec or even a partial null, but there is no mention of this in the literature. I have never seen service info for the early RCA encoder and have no idea what the alignment instructions were, if any.

You also have to realize that NTSC specs were predicated on a flat-top IF with sharp sound carrier trap. The phase/group delay characteristics of this standard IF were built into the FCC spec by a phase-compensating "Fredendall" filter at the transmitter. However, set manufacturers soon abandoned this IF design for a "haystack" response that had some of the standard phase response (especially near the sound trap), but was not identical. PAL specs did not include a phase compensation at the transmitter, expecting that phase distortions on color transients would be cancelled by the PAL technique.

[zenith2134]

What I'm trying to figure out is how much of a perceptible improvement would it have made to modify the encoder spec; then changing the IF scheme to accommodate the change in bandwidth. RCA was engineering for engineering's sake, since they had to realize that the FCC was not about to allow modifcation of the spec, which was so widely used worldwide at the time.