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I honestly cant beleive i did not give up!, the fairrite core broke when putting apart as i heated it a little, and it seemed to weaken it, although it came out easily, it crumbled quite easy, and then having to guess the windings etc, i even think the wire was a slightly bigger diameter, but who cares, its IT WORKS! **broken link removed** **broken link removed**
I turned it on a few hours ago, and no scan line on the screen.
I opened it, and i think the driver transistor for the transformer may be causing problems, i havnt tested the newly wound transformer to see if it has burnt out, but i noticed that the driver transistor's instuator had got a little melted, and i think the collector may have earthed through to the heatsink and chassis, after testing with a multimeter, it had a low resistance to the earth, so i think this may have been the cause for the transformer to blow up in the first place, although the transistor tests ok, i think i will replace both the transistor, and if i have to, replace the transformer. Anyway, ill keep ypu posted
mvs sarma said:
WoW, We enjoy Nzoomed. Finally You did it. CONGRATS
Hi,
at first, this is an old thread, so I will not have a look at it all the day.
Even your last activity in this forum was end of 2009 I contact you this way.
So if you have an answer please give me a note at a_coloniaatweb.de. (replace at with @)
I've also an OS-7020 and also my transformer was defect.
I tried several combination of windings. For testing I served the circuit by an external power supply. Starting by 0V turning up to 10V.
And what ever windings i tried, the flyback always rich the nominated -1900Volt at 8 to 10 Volt.
The scope works very well then. But the high voltage is very instable. By increasing the intensity the high voltage goes down to -1850 V. In result the deflection (x and y) increase too.
I've checked all around Q628 / Q629, it works in general.
Do you have your 7020 running well now?
If yes, could you send me scope pictures from the collector and basis.
Yes that looks like the transormer!
Unfortunatley with my scope was that it actually had an intermittent internal filament short in the CRT i discovered, which caused the transformer to burn out in the first place. I ended up throwing it out, but was a good learning experience anyway with regard to winding these transformers.
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