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  • Lets play with monitors!

    I’m currently repairing a game and getting it ready for Netherworld, but I ran into an issue that has become a pain.

    Basically what happened was I needed to remove the chassis for repair, but found I couldn’t budge the neck board from the tube. It’s obviously never been removed since it was installed, so being as careful as I possibly could, trying not to break either the neck, or the neck board I finally managed to remove it. The only problem was I’d also pulled one of the pins clean out of the tube along with it! Having a closer look I found that resin used to hold the socket must have run down into this one hole binding the pin solid. I plugged my rejuvenator into the tube to confirm the worst, and yep, it was now void of the vacuum all CRT’s need to work, so this CRT’s new home will be the local tip.

    Bugger!!

    This tube belongs to an Electrohome G07 and as such has a CR-23 pin out. These particular tubes are not that plentiful here in Australia, but what I do have quite a few of are brand new 48cm CR-25 tubes. These were commonly found in Nanao and Kaga Denshi monitors to name a few.

    So what to do....

    I guess this is as good a time as any to adapt a new tube to work.

    Firstly, I need to rewire the neck board socket to suit the new tube, easy, right!

    My test tube will be an old 510UKB22 that was originally paired to a Nanao chassis. I’ll also need to rewire the yoke plug to suit the G07 chassis.

    On power up for the first time I got a picture, but I quickly found I couldn’t get it to focus. In fact, adjusting the focus knob too far in one direction caused the spark gap that I had installed to start arcing, so I quickly backed it off. So my problem seemed to be the focus voltage was too high for this type of tube. Now we are talking about 5.2 to around 6KV+ here, and from what I could work out, I’d need about 5KV to give a nice sharp picture.

    So a little experimenting later, and close on 45 meg of resistance gave me a suitable voltage range for focus, and I now had a nice bright clear picture.

    So what’s next?

    Here’s my first thrown together modified board with the voltage divider fitted to lower the focus voltage.

    Neck board double adaptor, and other mods.

    Click image for larger version

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    In the mean time I’d been talking to [MENTION=974]dezbaz[/MENTION] about his tube adaptors, but he never produced a CR23 – CR25 adaptor, although he did have a prototype board and a spare socket, so these arrived today (Thanks mate!!)

    After a quick mod, and re-wire I fitted his board and fired up the monitor. I’m happy to say it’s working!

    What about the deflection yoke?

    The G07 shares the same principals with the Nanao here, both use a high impedance yoke. The only mod needed to the yoke is the plug, but I simply used a 4 way Molex connector to overcome this problem which also lets me swap between plugs.

    So what does this all mean?

    Well, unless you’re into using CRT monitors in your video games, it doesn’t mean much at all really. For those that do, 12 pin replacement chassis are no longer available from Joey [MENTION=204]Jomac[/MENTION] unfortunately, and I have also been trying to have the Nanao KZ-20EN LOPT (flybacks) reproduced, but without success so far. There are still a lot of 20” Nanao monitors in use, but once the LOPT’s fails, that’s it, and they are failing at an increasing rate. What this means is you can theoretically replace your non working Nanao with a G07 chassis and use your original tube. G07’s are available from the USA second hand and new LOPT are also available, and cheap.

    I guess for the average person this exercise is a lot of mucking around, but for me, it’s enable me to potentially build 14+ new monitors. I doubt I’ll ever need that many, but it's always good to have lots of redundancy.

    I’m also working on a replacement neck boards so I can more easily use these tubes (Thanks to Mike at [MENTION=4228]Homepin[/MENTION] for your help here!)

    Still lots to do, and remember, don’t try this at home unless you know what you’re doing. We are talking about some very high voltages here!!


    That mess in the first picture replaced with dezbaz proto board. This board made it so much simpler to work on!

    The high voltage probe serves 2 purposes, firstly to monitor the EHT (around 23KV) and it also discharges the tube on power down.

    Click image for larger version

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    Test picture of the monitor running. The picture is quite sharp, the photo isn't

    I have a more suitable resistor on the way, so once this arrives, I'll give the monitor a longer test run.

    Click image for larger version

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    Regards,

    Johns-Arcade.

  • #2
    Some great achievements made there.
    This knowledge is slowly disappearing and it's such a shame.
    Great to see forums like this and people like you keeping it alive

    Comment


    • #3
      Great write up John, thanks for sharing.

      I'm currently working at reviving one of those chassis atm and have a couple of spares with dead flybacks..

      Good to know there's another option.
      Namco Starblade - Taito Cocktail 14" x 3, 20" x 2 - NZ SI PtII Upright - Chase HQ DX, Taito Top Speed - Taito Grand Champion - Taito Safari - LAI SI Head to Head Cocktail - SI Cocktail Clone x 2, Pong Clone x 3

      Comment


      • #4
        Originally posted by toads View Post
        Some great achievements made there.
        This knowledge is slowly disappearing and it's such a shame.
        Great to see forums like this and people like you keeping it alive
        Thanks toads!

        It's more through need than anything else, but I an enjoying mucking around with this monitor.


        - - - Updated - - -

        Originally posted by Kaizen View Post
        Great write up John, thanks for sharing.

        I'm currently working at reviving one of those chassis atm and have a couple of spares with dead flybacks..

        Good to know there's another option.
        Thanks Adam,

        Give me a yell if you need a hand.

        Regards,

        Johns-Arcade.

        Comment


        • #5
          good stuff I'm about to attempt something vaguely similar, and will no doubt need to scan through in detail

          Comment


          • #6
            Your tube sockets arrived this morning:

            Click image for larger version

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            Comment


            • #7
              Originally posted by Homepin View Post
              Your tube sockets arrived this morning:

              [ATTACH=CONFIG]114205[/ATTACH]
              Very happy to see these!

              So from my PM inquiry 2 days ago as to whether you "might" be able to find me some, to here they are John!

              Who said things move slow in China!!

              Cheers Mike!

              Regards,

              Johns-Arcade.

              Comment


              • #8
                Great work John !!

                In effect the GO7 is an antique Kaga KZ20-ES which as you know has the same CR23 socket , so what you are doing in basically converting a KZ20ES to the KZ20EN.
                Knowing the flybacks are different between the 2 versions , the ES is the same spec as the G07 , hence why the focus voltage is to high , reducing the focus voltage is basically converting to a EN flyback spec.

                The G07 is a combination of both ,because while it has the CR23 neck board and is suited to a high impedance yoke like both the EN and ES it also has the pin correction transformer T503 and associated components , this is why you get a picture without pin cushion distortion ( hour glass ) .
                So basically you can plug the G07 directly into the standard Kaga , Nanao CR23 CRT and remove T503 then put 2 wire links in place of it.

                Plenty of different things can be done but as you have no doubt found it takes a lot of time and isn't a commercially attractive solution not to mention placing yourself as a business in a very tricky liable situation if someone hurts themselves or worse following even the most carefully produced instructions.

                I honestly believe there is still and will continue to be a big demand for a 12 pin CR25 chassis solution , plug a play that is

                Comment


                • #9
                  Originally posted by Jomac View Post
                  Great work John !!

                  In effect the GO7 is an antique Kaga KZ20-ES which as you know has the same CR23 socket , so what you are doing in basically converting a KZ20ES to the KZ20EN.
                  Knowing the flybacks are different between the 2 versions , the ES is the same spec as the G07 , hence why the focus voltage is to high , reducing the focus voltage is basically converting to a EN flyback spec.

                  The G07 is a combination of both ,because while it has the CR23 neck board and is suited to a high impedance yoke like both the EN and ES it also has the pin correction transformer T503 and associated components , this is why you get a picture without pin cushion distortion ( hour glass ) .
                  So basically you can plug the G07 directly into the standard Kaga , Nanao CR23 CRT and remove T503 then put 2 wire links in place of it.

                  Plenty of different things can be done but as you have no doubt found it takes a lot of time and isn't a commercially attractive solution not to mention placing yourself as a business in a very tricky liable situation if someone hurts themselves or worse following even the most carefully produced instructions.

                  I honestly believe there is still and will continue to be a big demand for a 12 pin CR25 chassis solution , plug a play that is
                  Thanks so much for the reply Joey.

                  It's great to know I have an alternative to my dilemma, and your post added a lot of info I was wondering about.

                  As you say, a commercial solution this certainly isn't, and it's certainly not a mod I'd recommend the average hobbyist tried. I do hope a solution for a replacement 12 pin chassis is found that is commercially viable, and plug and play, it really is needed.

                  Again, thanks Joey for the info you provided here, very much appreciated!!

                  Cheers!

                  John-Arcade.

                  Comment


                  • #10
                    Hi John! Great to see the mad scientists of the world are still at it. It seams I've been racking my brains for a solution to this. Was looking at doing similar but it's all theories at this stage and glad to see some results in this direction.

                    I read the thread a few times, did you have to remove the T503 that Joey spoke of?

                    Also, where did you put the resistor? (Physically). I can't make it out from the photos?

                    Cheers!
                    Last edited by taito; 3rd August 2017, 03:15 PM.

                    Comment


                    • #11
                      Originally posted by taito View Post
                      Hi John! Great to see the mad scientists of the world are still at it. It seams I've been racking my brains for a solution to this. Was looking at doing similar but it's all theories at this stage and glad to see some results in this direction.

                      I read the thread a few times, did you have to remove the T503 that Joey spoke of?

                      Also, where did you put the resistor? (Physically). I can't make it out from the photos?

                      Cheers!
                      The resistors are shown circled in the picture below. As Joey mentions, the transformer should only need removing if you were plugging a G07 into a Nanao CR-23 CRT set-up


                      Click image for larger version

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                      Regards,

                      Johns-Arcade.

                      Comment


                      • #12
                        Thanks for pointing out the resistors John.

                        I thought the test tube was from a nanao setup..510UKB22? I got me one of those.

                        Comment


                        • #13
                          Originally posted by taito View Post
                          Thanks for pointing out the resistors John.

                          I thought the test tube was from a nanao setup..510UKB22? I got me one of those.
                          It is, but a 510UKB22 is a CR-25

                          Regards,

                          Johns-Arcade.

                          Comment

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