EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: Daxxin on December 31, 2017, 03:39:35 pm
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I was planning to DIY this CRT rejuvinator , it was for sale as KIT from italian
magazine , they now close theyr business from years and that kit no longer
available from years too. The main problem its the T2 transformer they never
reveal the specification so its hard to guess , they called it in the article
modulation transformer , labeled TM1298.
At pin 12-13 of IC1 SG3524 we have 80khz squarewave thats driving mosfet MFT1
with DS1,Z1 and C13 forming an switching psu with an output beetween 8v and 20v
regulated by R15 used to modify the amplitude of squarewave , pin 3 signal
goes to TR3 that invert and drive IC2 that divi de by 2 circa 40khz this signal
this signal drive the half bridge IC4 and then this last one driving MFT2 and MFT3
connected to the primary of T2 at the secondary we get 400Vpp filter by C16-C17
and Z2 making it sinusoidal better as possible.
So hopefully someone can help me to identify and find an adequate transfomer
to replace it.
(http://oi65.tinypic.com/j6q0eg.jpg)
(http://oi68.tinypic.com/53s5dz.jpg)
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Rejuvenating CRT's involves blasting cathodic interface off by momentary traumatizing the CRT with a high positive voltage on the grid relative to the cathode. Ways to accomplish this can be fabricated very simply, but many B.S. circuits pretend to do this in some magical way and they are sold as something working superior to all other B.S. rejuv. circuits.
If you want 400V P-P just have one power transformer supply the necessary heater voltage to light the jug, then use one or more filament transformers with their secondaries in series(depending if you have 120V or 240V mains) stepping up the filament voltage to 240VAC again and then you will have an approx. magical 350-400VAC P-P at the secondary and this will be a just as good 400VAC sinewave as you will get from this B.S. circuit you post. All else that is required is a push-button switch and a current limiting resistor on the grid wire of the jug you wish to abuse.
I have accomplished rejuving CRT's just by simply charging a 10uF cap to 400V +/- 200V or so and discharging this cap through a current limiting 100-ohm to 1K resistor on the wire connecting to the grid, minus of the cap to the cathode. Works just as well. Put this simple circuit in a fancy box you can start your own crowd-starter entrepreneurship career and sell them and make millions.
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Oh, great. Looks like another Nuova Elettronica project, yeah? They were big for using custom transformers which only they sold. Of course they didn't publish voltage/material/winding details...
I helped someone a few years ago with a bit of reverse-engineering one of their projects using the "same" transformer part # - an electric fence controller, IIRC. Based on what I can find of the email conversation, I think we decided it was a laminated EI core @ ~400kHz (?!), 1-2-3 was ~400v p-p CT, the feedback winding 4-5 was 3~5v p-p, and 6-7 was ~15v p-p.
As I recall there were 4 or 5 projects that used that part number, and we figured out the above from hints/details spread across all of them. Try googling them for more info.
(edit: "same" in inverted commas because the guy I help suspected they used the same part # for different transformers using the same core. I wasn't convinced, but it may be true.)