CED VideoDisc and Player Discussion

[PapaPolynomial]

Hi all,

Just acquired my first Selectavision, a SJT-090. It looks to use the same circuit boards as the SJT-400. Indeed if you take the bottom cover off, solder points to the Composite Video and L/R Audio (plus "Control" signal) are visible on the circuit board right where the AV outputs are located on the SJT-400.

First thing first, I'm going to RCA outputs for each of these, but while my attention is fixed, I also want to run the Chroma & Luminance signals to RCA outputs.

I've read in the archives some other folks bringing this question up, some good information is contained within these threads, specifically regarding the use of the CA3216E video converter in all RCA models.

The datasheet for the CA3216E is handy to consult;

http://www.datasheetarchive.com/dlmain/Datasheets-112/DSAP0051429.pdf

Looking at the block diagram you can see the 3.53mhz Chroma signal is output from Pin 10. From there it is band-pass filtered, DC coupled & fed back into Pin 4. Inside the CA3216E it is then buffered/amplified but there is nowhere to tap this signal. So Either the Chroma signal at Pin 4 or Pin 10 needs to be amplified, I did some research and found a useful S-video amplifier on Ebay cheap; The Kramer PT-102S, which has indepedent gain controls for both luminance and chroma channels;

http://www.kramerelectronics.com/products/model.asp?pid=77

Rather than adding a amplifier internally, it seems to me to make more sense to run the Chroma and Luminance signals to some RCA jacks (I'll be installing a 6 jack board for Composite/Audio AV anyways), and amplify it externally.

So first question; Would it be better to tap the 3.53mhz Chroma signal at Pin 10 or Pin 4 of the CA3216E?

Moving onto Luminance, Pin 20 is where the Low-pass filtered signal of the "Combed Luminance" signal is fed. It is then amplified/buffered & clamped internally, and this resulting signal is available at Pin 21.

So Second question; Would it be better to tap the Luminance signal from Pin 20, Pin 21 or before the signal is Low-Pass filtered? It is my understanding, the LPF is needed to prep the signal for conversion to composite, and the luminance loses sharpness as a result. So if this is the case, should the raw Combed Luminance signal be used instead for best quality?

One final question, looking at the service manual for the SJT-400, the block diagram shows some noise reduction (called "Noise Coring") being applied to the video signals at some point. Does this happen after converting to composite? The Service Manual calls this signal "Player Video" (Vs. Composite Video).

Obviously, outputting the 3.53mhz Chroma is more straight forward. It may make sense to only add an output for this signal and to strip the luminance signal from the composite out, thats a 3rd possibility. That at least would give far better color rendition out of the Selectavision.

Looking forward to some nerdy discussion on the subject, surely something is possible!

Service manual for the SJT-400 can be found at;

http://arcarc.xmission.com/PDF_LaserDisc_Players/RCA%20SJT%20400.pdf

Using that in combo with the datasheet is useful.

Thanks All.

*I just found this should suit the purpose of taking the Chroma/Luma from RCA jacks to convert it to a standard 4-pin S-Video cable.
http://www.ebay.com/itm/141190918868

[kitchensynch]

The quality of the CED picture is good, but you'd be better off simply enhancing it. You are not likely to see a huge difference.
_________________
A New Vista of RCA Victor COLOR!

[PapaPolynomial]

Unlikely the RF output doesn't degrade the picture quality quite a bit, component outputs are a noticeable improvement, and s-video is one notch above.

s-video is like lab color, luminosity is sent seperate from the color channels it's sharper and has greater dynamic range and the color less muted.

I'll start hacking around to see if I can get at least a signal out, then I'd be happy to do screen captures for comparison.

[kitchensynch]

Remember that you need to host your images, there is no other image insertion routine for this board.[/img]
_________________
A New Vista of RCA Victor COLOR!

[PapaPolynomial]

I'm still trying to make this work. Pin 21 is the luminance output of the video processor "CA3216E", but the signal looks scrambled when trying to view it via my TV capture card via it's s-video input. *you can barely make out some video data. I should also note i experimented with an s-video amp with no success.

The datasheet i posted a link to above says that the IC "provides the primary functions of converting a "buried subcarrier" video signal to a standard NTSC format". That tells me the signal is not NTSC until the final composite output @ pin 2.

Not to be deterred...

The next thought i had was that I could cut the trace leading to pin 4 (3.58mhz Chroma Input) and run the b&w composite out (pin 2) to the luminance pin of my svideo capture card. This actually worked, though i think leaving pin 4 floating is causing the video signal to be a little shaky now, think i need a tie-down resistor to ground.

Haven't tried the chroma signal yet, but i'm hoping i can just use the 3.53mhz chroma signal that used to go to pin 4 for the color, since the sync data is on the luminance channel.

Anyone else familiar with this?
_________________
SJT-090, SJT-300