In Car TV (CRT, yes CRT) Help. - Page 1
Forum section: electronics / projects

author: derekjay
author_rank: Newbie
timestamp: July 14, 2014, 12:50:25 am
content: BackgroundI am currently working on a project to restore aToyota Soarer MZ12from 1985. It was the first car to have an in dash TV (obviously CRT).Here is a page detailing the TV and Driver system.ProblemThe CRT appears to have given up. When I had the CRT plugged in, I could vaguely see the Multivision display, but it appeared ghostly, and looked like the CRT tube was not happy.SolutionReplace the CRT with an LCD. But to do this, I need an LCD of the right size, LCD driver board, and something to convert what was being sent to the CRT into something that the LCD driver board can use.Conundrum/QuestionHere is what I know so far:http://yojiko.com/yo/ji/ko/pw/EMV_to_LCD-Part_1and Here are the circuit boards:http://mz12gt.com/?p=293The last point of the driver box are two chips.AN5315andAN5352.The AN5315 takes a composite video signal and converts it into "color difference" signals. B-Y, G-Y, R-Y and Y(Y is luminance).The AN5352 takes a teletext character signal in R, G, B and adds it to the B-Y, G-Y, R-Y and Y output of the AN5315. Here is what I see when I run the teletext character signalthrough aJamma boardinto a monitor. There is something.What I want to know is. How do I convert the B-Y, G-Y, R-Y and Y or RGBS to something I can see on a monitor?Here are some things I have tried:I have tried running the B-Y and R-Y and Y signals into the Jamma card, via YPbPr connections, but get junk, I think because the Y is missing the sync. Here is a videoI have tried adding the sync to the Y channel using the circuit described here:http://www.raphnet.net/electronique/sync-on-green/sync-on-green_en.phpbut instead of adding the sync to the green adding it to the Y channel. This did not work, either because, I used the wrong sync (the TV driver board seems to offer 4 syncs, sync for the teletext signal, a combined sync (I think), H-Sync and V-Sync (I think)), I used what I thought was the combined sync, or the circuit doesn't work for adding sync to Y, or my prototype building skills suck. Does anyone know if this should work?I have tried to use the RGB signal that feeds into the neck of the CRT tube as input to the Jamma board. There seems to be a circuit, that adds the Y channel back into the R-Y, G-Y, B-Y channels, with adjustment, just before it is sent to the tube. Does anyone know if this would be a suitable place to source RGB for an RGBS input to the Jamma card? (it doesn't seem to work) Can anyone supply me with a diagram of a circuit that would add Y back to the R-Y, G-Y, B-Y channels? The one on the board before the CRT seems overly complicated as it has adjustments for brightness, which I don't needI have tried scoping the RGBS.http://yojiko.com/yo/ji/ko/pG/EMV_to_LCD-Part_2SyncColour and SyncI have tried feeding the RGBS signal that was going into the AN5352 into the Jamma board. Which occasionally shows a frame grab, but won't lock on.Here is a videoI have also tried using a variety of sync cleaning methods:http://yojiko.com/yo/ji/ko/pY/EMV_to_LCD-Part_3_More_Hardwarenone of which seemed to work. And in fact were worse than not using it. The RGBS signal would occasionally show a frame grab, but running through any of the sync cleaners I tried, I got nothing.TLDR;Does anyone have any experience with hacking TV circuitry especially colour difference circuitry? What is the simplest way to get the output of a AN5315 chip to produce something I can convert to VGA to power an LCD? Alternatively what is the simplest way to get the input to an AN5352 to convert to VGA to power an LCD?Here is a video of an actual working In Car TV from a MZ12 Soarer:Research shows that the AN5352 chip was used in the Commodore Amiga 1080 monitor Manual here The block diagram indicates to me that RGB inputs to the AN5352 work completely independently of the R-Y, B-Y, G-Y inputs that it takes from the AN5315 chip in my board. Which means I can just tap those inputs.The upscalers/converters I have tried are GBS8200 and GBS8219. I have been able to get signals out of the GBS8200 but never managed to get anything out of the GBS8219 (despite it costing more and being advertised to handle a wider range of inputs).

author: amyk
author_rank: Super Contributor
timestamp: July 14, 2014, 10:02:20 am
content: What horizontal/vertical frequency does it run at? Is it interlaced? If it's close enough to VGA timings (and often, even if it's not) multisync VGA scalers will have no trouble with the signal.The AN5352 datasheet has an application circuit at the end that shows it driving a CRT through some circuitry; it might be easiest to take the analog RGB from where it drives the tube (dividing it down to VGA levels) and sync from the horizontal/vertical deflection circuits.

author: Scrts
author_rank: Frequent Contributor
timestamp: July 14, 2014, 10:51:28 am
content: You would need a video encoder, which would have analog inputs. These encoders usually have YUV output (you may find some RGB ones - check the manufacturers like ADI or TI), so then you need to change the YUV back to RGB and supply this directly to the LCD panel. This can be done by FPGA easily.

author: derekjay
author_rank: Newbie
timestamp: July 14, 2014, 10:22:05 pm
content: Thanks for the ideas.I can definitely scope the RGBs signal coming out of the computer in the boot. So far I have tried:GBS8200GBS8219Additionally I have used LM1881 sync cleaners to clean the sync signal.None of these have produced a usable signal.Additionally, it is getting quite expensive trying this stuff, so I would like to know if there is a sure fire solution to the problem. Or even a way I can diagnose what is going on.Do people have recommendations on RGB to VGA converters?

author: amyk
author_rank: Super Contributor
timestamp: July 15, 2014, 12:26:14 pm
content: Quote from: derekjay on July 14, 2014, 10:22:05 pmYou have a scope, make measurements of the signal timing that I wrote above. What you can do next depends on how close to VGA it is/what the montor you'll be using can accept. The conversion circuit could be as simple as a few passives and transistors, or you might need a full framebuffer-type scan converter.

author: derekjay
author_rank: Newbie
timestamp: July 15, 2014, 12:29:59 pm
content: Quote from: amyk on July 15, 2014, 12:26:14 pmOk. Will do.

author: Tantratron
author_rank: Frequent Contributor
timestamp: October 31, 2024, 04:53:52 am
content: Quote from: amyk on July 15, 2014, 12:26:14 pmhelloamyk, I'm having the similar challenge where I'm trying to replace a CRT unit from an Advantest R3361 spectrum analyzer, the video signals are RGBS interlaced at 15KHz.I have purchased an arcade RGB to VGA board which does the rescaling fine then its VGA output connected to a 640x480 LCD driver based on RTD2660 panel chip controller.It seems the RTD2660 found say in PCB800099 board could do the de-interlacing but it requires a specific firmware not easily found.When you wroteyou might need a full framebuffer-type scan converter,do you mean an Arcade conversion board or do you know of another method to de-interlace then produce a valid VGA signal at 30 KHz ?Thank you, Albert