Rare field sequential color device

[etype2]

1993

Mitsubishi HSCX6 Field Sequential Color Monitor.

Just found this rare oddity, a field sequential color monitor attached to a camcorder! I have little interest in the camcorder and quickly removed the monitor from the body of the camcorder and opened it up to find out how it works. I may need the camcorder as a backup to power the monitor, but it’s my goal to create a stand alone miniature monitor curiosity for display purposes. It requires a 6 volt power supply or 220 volts mains supply. It uses a 6 segment color cone which is angled in front of a 0.7 inch monochrome CRT, quite possibly the smallest CRT made. The cone is attached directly to a motor by drive shaft which spins at high speed to fool the brain in seeing a flicker less full color display. Mitsubishi claims this approach offers higher resolution and brighter images compared to the beam index or LCD methods, because there is no shadow mask or color dots used.

For a small-sized high quality color monitor using this system, the NTSC video signal (simultaneous signal) was converted into the video signal of a field sequential color display system. Mitsubishi decided to separate the NTSC signal into three primary color video signals, and display them sequentially in each field to achieve the field sequential primary color video signal . The frame frequency of the signal is 10 Hz (1/3 of that of an NTSC system), less than that formerly used in the 1951 CBS system, 24 Hz. So it is not acceptable because color flicker is conspicuous . In order to reduce the color flicker to the same level in NTSC, Mitsubishi decided to display the separated primary color video signal sequentially in each field after time compression by 1/3 , and increased its frame frequency by 3 (three) times (to 90 Hz). Using this method , the same level of frame frequency as that of an NTSC signal is achieved.

We will update this post after we get the monitor operating. We have full schematics and hopefully the monitor components are not damaged. Stay tuned.

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Scroll down to bottom of this page to see all photos. https://visions4netjournal.com/page-five-trinitron/

[old_tv_nut]

It would be interesting to know the sampling frequency and bit depth of the digital processing for the field store.

[etype2]

I don’t know the answer, but under the brass cover, we find three identical Ram chips. We believe they process each primary color. I found the data sheet which may offer a clue.

https://visions4netjournal.com/wp-co...TSS08971-1.pdf

https://visions4netjournal.com/wp-co...F15D85BCB0.png

[old_tv_nut]

It appears that the bit depth is 6 bits (18 bits per pixel). It's not directly stated whether rows/columns correspond to TV samples/lines or vice versa, but the number of each implies rows = samples and columns = lines. So, 320 samples per line and 256 lines. This is plenty of lines for NTSC, and about 11% short for PAL/SECAM. 320 samples per line cuts the horizontal resolution to about 45 to 50% of broadcast resolution, depending on how much aliasing you accept. However, since this a VHS-C device, it's analog resolution is already in that range, so the sampling is not a significant limitation.

[etype2]

Here is a block diagram.
https://visions4netjournal.com/wp-co...7BC41CED0.jpeg
They used a cone to save space and Mitsubishi claims “color breakup” (rainbow effect on edges when the display is juggled) has been reduced and a shorter interval time between switched colors reduces flicker.
https://visions4netjournal.com/wp-co...104514518.jpeg

[MadMan]

I guess it was just that damn important for them to have a color viewfinder, and LCD's kinda sucked back then. Always amazing the crazy crap engineers can come up with when they're stuck in a hard place like that.

[etype2]

I think so. A challenge and a game of one ups man ship I think, as the Hitachi index viewfinder came 8 years earlier. These oddities are interesting to me.

Mitsubishi advanced the art on paper with this thing, but it will be a challenge to get it working, not going to lie.

[AlanInSitges]

Originally Posted by etype2

https://visions4netjournal.com/wp-co...104514518.jpeg

That is one beefy yoke.