View Full Version : World's smallest color CRT


etype2
04-27-2014, 11:40 AM
I just completed a little project of turning the tiny Hitachi 1.25 inch color viewfinder into a video monitor. I know some of the viewers have already done this, thought it would be fun to try. Want to thank Jerome Halphen, John Folsom and jr_tech for their help.

Instead of posting a load of photos, easier to check this link: http://www.visions4.net/journal/time-line/page-two/page-two-a/page-three/page-three-a/indextron/

Is there UV or radiation danger from this CRT?

The image is reversed on the CRT screen, but corrected by the mirror which reflects the image out the magnified eyepiece. Is it possible to reverse the image to normal on the screen so text can be read?

http://i184.photobucket.com/albums/x117/etype2/imagejpg1.jpg (http://s184.photobucket.com/user/etype2/media/imagejpg1.jpg.html)

EdKozk2
04-27-2014, 11:56 AM
Hi,
Try reversing the horizontal deflection coil connections. That should change the scanning direction. Make sure the connections are isolated from The B+ and ground, that way you won't burn any thing out.

EdKozk2
04-27-2014, 12:11 PM
Cool website, lots of info on the kind of equipment that may turn up in thrift stores these days.
Ed

etype2
04-27-2014, 12:34 PM
Thanks for the info. Gives me a start, Will try to figure it out.

Elkhorn WI? I used to work there from 1972 to 79.

jr_tech
04-27-2014, 01:25 PM
Hi,
Try reversing the horizontal deflection coil connections. That should change the scanning direction. Make sure the connections are isolated from The B+ and ground, that way you won't burn any thing out.

That *should* get the scan going in the proper direction so that the printed material will be correct, but the beam will be crossing the color stripes in the wrong sequence relative to the "index stripe" so the colors will likely be wrong. Perhaps rotating the tube 180 degrees in the yoke after swapping the horizontal deflection connections will restore the proper stripe indexing sequence. :scratch2:
jr

etype2
04-27-2014, 06:47 PM
That *should* get the scan going in the proper direction so that the printed material will be correct, but the beam will be crossing the color stripes in the wrong sequence relative to the "index stripe" so the colors will likely be wrong. Perhaps rotating the tube 180 degrees in the yoke after swapping the horizontal deflection connections will restore the proper stripe indexing sequence. :scratch2:
jr

Thanks for that.

There are two index stripes, green and UV, and there are two photodiodes to "read" them. Do you know which one reads the UV index emission? The amber or the black one?

EdKozk2
04-27-2014, 07:22 PM
Sorry, I've never worked with a view finder circuit. I see where JR Tech brought up a good point about the correct color stripe being scanned first. If you had a monochrome tube it wouldn't have mattered.
ED

colorfixer
04-27-2014, 09:22 PM
If one were to swap the two photodiodes in addition to the horizontal deflection coil connection polarization, it would change which photodiode was used as the "start" index, and which was used as the "stop" index?

etype2
04-28-2014, 09:13 AM
If one were to swap the two photodiodes in addition to the horizontal deflection coil connection polarization, it would change which photodiode was used as the "start" index, and which was used as the "stop" index?


I have two of these CRT's, one is to experiment on. I could remove the photodiode module and turn it 180 degrees to see what would happen. Edit. Whoops .... That would be impossible. The module would face the wrong direction.

centralradio
04-29-2014, 03:21 PM
Thanks for sharing .I forgot about the Indextron format.

For awhile I thought the Panasonic CT-101 was the smallest color CRT TV set.I have the CT-101 which has a problem with a vertical line on the screen.

etype2
04-30-2014, 09:15 AM
Thanks for sharing .I forgot about the Indextron format.

For awhile I thought the Panasonic CT-101 was the smallest color CRT TV set.I have the CT-101 which has a problem with a vertical line on the screen.


I have the CT-101 as well, very nice set. I measured them both, the Panasonic appears to be 1.4 inches viewable.

The vertical line, probably bad leaking caps. There are several threads on the set here.
http://www.videokarma.org/showthread.php?t=255690

colorfixer
05-01-2014, 12:23 PM
I have two of these CRT's, one is to experiment on. I could remove the photodiode module and turn it 180 degrees to see what would happen. Edit. Whoops .... That would be impossible. The module would face the wrong direction.

Well, not exactly: you would want to swap the connections from the respective photodiodes: the "start" diode would be connected to the "stop" photodiode's connector, and vice-versa. Thus the "start" signal which would be referenced by the first index phosphor would be generated from the first stripe the beam hit as it scanned, and the "stop" would therefore be generated and detected by the beam hitting the second index phosphor. Remember that the index order would be reversed if we forced the beam to sweep in the opposite direction by reversing the yoke connections.

wa2ise
05-01-2014, 03:45 PM
You could leave the horizontal alone, and reverse the vertical yoke connections. Then the indexing is still valid.

jr_tech
05-01-2014, 11:53 PM
You could leave the horizontal alone, and reverse the vertical yoke connections. Then the indexing is still valid.

Slaps forehead !
I think that you have nailed the best solution!

jr

etype2
05-02-2014, 09:37 AM
Thanks. Can you you explain so that a person who has never done this before could understand. So just reverse the vertical yoke connections and nothing more?

Electronic M
05-03-2014, 06:35 PM
Reverse the vertical connections and flip it upside down and you will see a viewable picture with readable text.

Before I read wa2ise's post that was what I was going to advise you to do....Now it's more of a clarification than advise.