Nanao MS-2931

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    • I tried one of these new replacement flyback transformers on a working MS-2931 chassis yesterday.

      Before installing the new replacement flyback I tested the chassis with the original Nanao flyback first. Everything looked fine.

      Desoldering the original Nanao flyback went smoothly.

      And it came out without much fuss.

      New replacement flyback was soldered in. Note the three circles in red. These are actual pins on the orignal Nanao flyback and on the new replacement flyback they are stiff wire which you have to carefully position into place whilst aligning the pins of the flyback through the holes on the board.

      New replacement flyback installed. Note one of the stiff wires bottom right of the flyback.

      I connected everything back up on the chassis and carefully powered it on, ready to turn it off immediately if I heard any high pitched squeals or buzzing, but instead I was greeted with this disappointing image.

      I then remembered that I would need to adjust the focus pot on the new replacement flyback. I got out the mirror and was able to get the focus nice and sharp.

      Looking good, but I noticed the vertical and horizontal sizing was off. I reduced both vertical and horizontal sizing to zero via the OSD menu which produced this result :

      Vertical size is about spot on, but the horizontal size is still too wide and probably needs to be reduced by another 5% or so.

      I then tested B+ and it read a little low at 178.4V. I adjusted this up slightly to 180V but made no difference to the horizontal sizing. I then went into the "FACTORY" menu and played around with the vertical and horizontal limit size, but this didn't seem to make any difference. Perhaps I'm missing something... One other thing that I tried (and I STRONGLY recommend against trying this as it can kill your chassis) was adjusting the Horizontal Drive pot slightly, this also made no difference.

      I then turned everything off, discharged the CRT, removed the chassis, desoldered the new replacement flyback and soldered back the original Nanao flyback and connected everything back up again. Using the same horizontal and vertical size settings, you can see the difference compared to the original Nanao flyback.

      I adjusted the vertical and horizontal settings back to their original settings for the original Nanao flyback.

      So to summarise, these new replacement flybacks do exist and do appear to work (I ran the chassis for about three hours with the new replacement flyback) without any squealing or buzzing, however they don't appear to be a 100% match due to the vertical and mainly horizontal size issue. Someone smarter than me might be able to suggest a change of value with a resistor or capacitor on the MS-2931 chassis to improve the horizontal sizing when used with the new replacement flyback. Perhaps this would be easier to solve with a MS-2930 chassis as I imagine you could change the value of the h-size pot to fix the issue.

      I'd be interested to hear how other people go with their new replacement flybacks and if they run into the same issue I had.