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I believe it is a Wei-ya 814sr model.
It's a Rodo Tron. Note the "CH-203" printed at the corner by the flyback.....that's a Rodo Tron model number.
Rodo Tron made "generic" replacement chassis....as well as other companies "re-branding" them, as mentioned Pentranic.....and also Eygo, Promax, and a slew of other here today-gone tomorrow companies.
Edward
OK, it's a generic replacement chassis of some sort. Used by an unknown number of fringe monitor manufacturers. Next step is figuring out how to use it on a monitor; Is there a way of determining the output impedance to match it up with a yoke or should I just hook it up and watch for smoke?
OK, boys...I dug thru my piles of crap and pulled out a new Happ 1901MG that doesn't work. I hooked her up to the chassis and fired it up. I get a gorgeous picture (man I miss new crt monitors) but the picture is too short. Max vertical height only fills about 2/3 of the screen. Has to do with yoke impedance, I'm sure. Any ideas on how to fix this? The flash doesn't do the picture justice but here's what I got............
Out of interest, if you measure the resistance on the Vertical yoke, what's the reading come out at ? My notes say the MTG-1901 measured 14 ohm vertical with the stock yoke.
- James
Let's say the chassis has a higher output "impedance" of 50 ohms. I mate it to a low "impedance" 15 ohm yoke. The chassis cannot put out enough current to match the yoke and creates something of a brownout. The result is not enough current going through the yoke and therefore not enough vertical deflection. Is this thinking sound?
I have the exact chassis sitting in an old Go7 frame and tube..
That should give you a good idea on what yoke to use![]()
Also the inductance of the vertical yoke also comes into play. But basically the impedance and inductance of the yoke need to be close enough for the vertical drive to end up with enough current in the yoke.
Both the impedance and inductance of the yoke effect the voltage across the yoke from the vertical drive, which has a fixed supply voltage. This will have been designed to produce a peak current in the yoke for the maximum deflection. If either is way off the calculation fails and yoke doesn't get enough current for complete/correct deflection. Adjusting the vertical drive supply and feedback for the vertical amp ultimately effect the current in the yoke and the deflection that's possible. I think I'm saying that correctly. I'm sure someone will correct me if not![]()
There were/are some application notes from Philips in the 90's detailing the calculations for their TV semi's and how resistance, inductance, voltage and current all factored in to the design for a given yoke.
- James