Wiz
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Sep 10, 2005, 11:56 PM
Post #5 of 14
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When I did it, I just used a bit of mains wire, wraped around the flyback, underneath the ferite core. Only do 2 winds though, even though the output of these leads is much less than 6v when measured on AC meter. This is because the wave form of the flyback isn't sinusoidal. The ends of the wires, you connect to the heater track of the tube board, between the pins and the break in the track.
Disconecting the heaters, and puting them through your own 'mini transformer' completely isolates the heaters from ground. This will fix the problem because the 200v on the cathode, is being pulled down to 6v, thereby making the difference between the cathode and anode greater, and therefore making one colour very bright. By isolating the heaters, when the short occurs, the heaters will be brought up to the 200v. Because this is 200v has no current, the heaters see the 200v as 0v, so to them the alternating 6v from the 2 turns is still as normal.
Hope this helps,
Oliver
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Toshiba 2987DB
Thanks for that. Can you give me some more information as to how to 'wrap 2 loops around the flyback transformer? (Insulated/bare, what gauge, what part of transformer), and where to reconnect? I may be misreading your post, but if I isolate the heater pins, then attach a wire which only loops twice through the flyback, surely the heater pins would be redundant? 
Brilliant. I think I've got most of the procedure clear in my head. Before I cut the heater tracks though, Can I just confirm that they are the 2 uppermost pins on the 'circle' of pins attaching the CRT to the PCB , and both marked 'H'. 
OK, I did this today. The good news is it still powered up and I got a picture. The bad news is it only lasted a couple of minutes, then the screen went blue with diagonal white lines, and it powered off again. Back to square one.