Elesta Visulesta 4 crt replacement with LCD panel
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    Default Elesta Visulesta 4 crt replacement with LCD panel

    I have an Elesta Visulesta 4 DRO with Heidenhain scales on a Swiss made Scheu surface grinder I am refurbishing. The crt in the Visulesta is beginning to flicker and change brightness and I suspect the crt driver section. I am investigating replacing the crt with a LCD panel. I have two options. A company in Germany sells a plug-in replacement which is a 6.4” lcd and a conversion board for about $1200. That is too much for my budget so I am looking into rolling my own. I am curious if anyone else has crossed this bridge and has info on doing this?

    My next step is to put an oscilloscope on the back of the circuit board edge connector that goes from the digital display section to the analog crt driver board to figure out what signals are on the 10 pins there. It would be nice if someone has already done this so thought I’d check first....
    -Tom

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    Well, ok then. For the record this is how the 10 pins on the edge connector (all black wires) read from top to bottom. On my unit they are labeled on the circuit board as A,B,C,D,E,F,H,J,K,L.

    A. Ground

    B. -12 VDC

    C. -50 VDC

    D. -12 VDC

    E. Ground

    F. Signal Amplitude about 3.4 VDC @ 24.51 kHz - This is Horizontal Sync signal...

    H. +12 VDC

    J. Signal Amplitude ~4.0 VDC - Digital Video Data signal...

    K. Signal Amplitude ~3.4 VDC @ 58.82 Hz - This is Vertical Sync signal...

    L. Ground

    A horizontal sync frequency of 24.51 kHz is not one of the old standard graphics sync rates. Not MDA (18.432kHz), not CGA(15.75kHz), etc. So next is to find a solution for the conversion of that to VGA to feed to a generic 6.4" panel...

    -Tom
    Last edited by tome9999; 01-15-2019 at 02:05 PM.

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    To continue talking to myself on this project...

    I purchased a XVGA Box: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
    This is based on the GBS-8219 board. You can find the GBS-8219 board alone, or even this same one, cheaper from China. In the end I will end up removing this from the case to mount inside the DRO. This board decoded the video from the Elesta Visulesta 4 with ease. From what I have seen/read about these boards the cheaper GBS-8200 board will not work with TTL video output so don't be fooled into buying the cheaper board - or if you do and it works please do tell.

    I tried a couple different LCD screens. I am going to go with this one: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
    It is cheap, works great and is the right size for the display and to fit in the enclosure. The driver board is the same one used on many small VGA monitors out there with the same software menus. Again, I don't need the plastic cases, speakers, etc., that come with other more expensive monitors so this bare bones display was a good find.

    I can connect my video to any individual R,G, or B input or any combination of them. I think green looks best. White or yellow are also not bad, but I will probably just go with green. RGB are additive colors so combining G and B gets Cyan, R and B is Magenta, and G and R is Yellow. The original CRT was Amber.

    It turns out I am able to drive the LCD as well as the XVGA decoder board from the Visulesta +12VDC and GND pins. I don't know how much current the DRO supplies on the 12V rail but it had no problem powering these two devices. I believe the display needs about 1 amp max, and the decoder requires a max of 400mA.

    I removed the CRT and it's driver board from the DRO enclosure today. It was kind of a pain. There isn't much space in one of the corners to get to the nuts that need to be removed. There are 4 M4-0.7 threaded rods screwed (and apparently glued) into studs that are on the back of the face plate that are used to mount the CRT and hold it against the bezel and front of the enclosure. I was able to get two of the them out but the other two broke off inside the studs. So I wont be using those to hold my display down. I will have to improvise. I didn't discharge the CRT because I didn't want it damaging the other electronics in the DRO so I had to be careful not to touch or short the high voltage connections on the crt and driver board. That also didnt help to get out.

    I am now working on the cabling, bezel, and brackets to hold the screen and the circuit boards in place. I took measurements from the current bezel and will draw something up in cad and either 3D print it or figure out some other way to fab it up.

    Attached are some pictures. I circled in red the connector on the video board that I will be connecting to. Another pic shows the wiring off that connector from top to bottom.

    -Tom
    Attached Thumbnails Attached Thumbnails img_7468.jpg   img_7470.jpg   img_7491.jpg   img_7483.jpg   img_7482.jpg  


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    Congratulations Tom, you are now this forums world wide expert on this DRO. All future questions about it will be sent to you. You didnt know that was a side benefit from this forum did you? I hope you get it all working to your satisfaction, it has been fun to read even though I dont need to know any of it. You did a great job explaining what you were doing.

    Charles

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    By the way Tom a few years ago there was a big discussion about changing out CNC screens. This was in the Deckel subforum and it was also interesting. I dont know if any of that information is still relevant but as you seem to have found your solution it probably wouldnt really help you anyway.

    Charles

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    I realize that this is late to the game but did you give any considarashion to just replacing the CRT? I have had a lot of luck finding weird electronic parts on eBay punch in the part number and see what comes up.

    Reading your first post again I see you think your problem is with crt driver section. Try punching in the part number for that board in eBay and see what comes up.

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    Quote Originally Posted by CBlair View Post
    Congratulations Tom, you are now this forums world wide expert on this DRO. All future questions about it will be sent to you. You didnt know that was a side benefit from this forum did you? I hope you get it all working to your satisfaction, it has been fun to read even though I dont need to know any of it. You did a great job explaining what you were doing.

    Charles
    Ha. Yeah, expert...? Once I get it back together I still need to figure out how to operate the thing :-)
    -Tom

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    Quote Originally Posted by SIP6A View Post
    I realize that this is late to the game but did you give any considarashion to just replacing the CRT? I have had a lot of luck finding weird electronic parts on eBay punch in the part number and see what comes up.

    Reading your first post again I see you think your problem is with crt driver section. Try punching in the part number for that board in eBay and see what comes up.

    Nah, I went straight for the more difficult approach! I have a friend who could probably diagnose and repair the existing CRT issue, but what fun is that :-). Sometimes once you start down a road it's hard to go back...

    -Tom

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    Built the wiring harness using the connector that was there. Just needed +12VDC and GND to power the two boards, and Vertical Sync, Horizontal Sync, and Video signal. I mounted the video decoder board (out of its case) onto the metal plate where the CRT driver board was previously mounted.

    I played with putting a potentiometer on the green signal and connected that and the red signal up to the video input and tuned the pot to get amber. But in the end green or white has better contrast so I am going with green.

    I drew up a bezel in Autodesk Fusion 360 and 3D printed it on a Formlabs Form2 printer and am in the process of painting that. I am currently printing the bracket that attaches to the back of the bezel to hold the screen down flush and provides a place to mount the circuit board.

    Once that is done the only thing left will be figuring out how to keep the bezel in place since 2 of the studs that were used to hold the original CRT in place are plugged up with broken off screws. I will also need to shorten the VGA cable or find a ribbon cable or very short one some where.

    -Tom
    img_7550.jpgimg_7554.jpgimg_7553.jpgimg_7552.jpg

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    Nearly ready to reassemble the DRO. The 3D printed bracket is complete. I am going to use silicone caulk to glue the bracket to the metal frame. The fit is very good and I think the silicone will hold it in there tightly. Attached are some pics of the bracket.
    -Tom

    img_7564-.jpgimg_7576.jpgimg_7573.jpgimg_7574.jpgimg_7569.jpg

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    All back together and operating. I used silicone caulk to glue the bracket to the metal shell. Works well and is very secure. I had white caulk laying around that I used. In retrospect I should have gotten some clear. You can see the white caulk around the bezel. Will have to touch it up with a Sharpie or something.

    Now on to figuring out how to operate this machine!

    Thanks for listening 😉

    -Tom


    09c08503-f17a-4ca3-93e2-0edb6af031d8.jpg62cc8925-8962-41df-9d23-caa682b83a1e.jpg

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    Great thread.I have a turnvision that's going to need a crt conversion, very interested in how you did this.

    I didn't discharge the CRT because I didn't want it damaging the other electronics in the DRO so I had to be careful not to touch or short the high voltage connections on the crt and driver board.
    Can you elaborate on how to do this? If the DRO has been dormant for a long time do you still need to discharge the CRT?

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    Quote Originally Posted by Mud View Post
    Great thread.I have a turnvision that's going to need a crt conversion, very interested in how you did this.



    Can you elaborate on how to do this? If the DRO has been dormant for a long time do you still need to discharge the CRT?
    Most CRTs, unless they are very old, will usually have a bleed resistor to discharge the tube. Mine probably does as well but I don’t know for sure. If there is no bleed resistor though a crt can hold quite a charge for a very long time. You can search YouTube for “discharge crt” to see how it’s done.

    The easiest way is to slip a long screwdriver under the rubber cap on the side of the tube and short it to the frame. We always did this when we worked on Telray Terminals back in the 80s at the Univ. I attended and worked at. The downside is that the spark can potentially damage any nearby electronics. In practice I don’t think that ever happened but I didn’t want to take the chance on the Visulesta...

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