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Author Topic: Hantarex MTC900E yoke reading too high  (Read 2071 times)

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snappleman

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Hantarex MTC900E yoke reading too high
« on: August 19, 2021, 06:18:46 pm »
Doing a tube/yoke swap and the yoke on this hantarex 900e is reading 27.1ohm/300mH vertical. Horizontal is correct. I can just use the yoke from the donor tube but as far as I know this is not right for this yoke, yes? I found a repair doc by Ken Layton that reads:

Yoke Resistance:
Vertical (15 ohm) Pin 1 Brown and pin 2 Red
Horizontal (2.5 ohm) Pin 5 Orange and pin 6 Yellow

so I assume something's gone wrong. Any way to repair this if it is busted?

princess prin prin

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Re: Hantarex MTC900E yoke reading too high
« Reply #1 on: August 21, 2021, 01:18:54 pm »
Looks like one of the vertical coils went open as resistance is double what a normal one is supposed to be. Is it an Orion tube?

snappleman

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Re: Hantarex MTC900E yoke reading too high
« Reply #2 on: August 21, 2021, 03:32:31 pm »
The tube is a Sharp, I'm pretty sure this was already swapped when I got it. Maybe I should explain more:

I got the monitor not working, chassis in need of repair. Powered it on, nothing.

I plugged the monitor into another identical good chassis to test it, heard a pop, powered it off, inspected things, no visibly damaged components.

Started testing the tube, noticed the yoke readings were uncommon on the vertical, found Ken's guide.

Put that good chassis on its good (but extremely burned in) tube, image is now very washed out with retrace lines, flyback still adjusts the brightness but doesn't go black, and the retrace lines are there even at the lowest screen level. Also has excessive high voltage to the anode (huge pop on discharge when this monitor barely makes a tick usually). So I'm guessing the shorted yoke took out some components, maybe a voltage regulator or even damaged the flyback. Not sure but it did smell, and not the popped flyback ozone smell but more of a burnt diode/resistor/IC smell.

I'm guessing the yoke is what took out the bad chassis (or the bad chassis took out the yoke, chicken+egg), and it's taken out the good chassis now too. I have no idea what a shorted yoke does to the rest of the monitor so I would appreciate advice on where to check.
« Last Edit: August 24, 2021, 12:14:25 am by snappleman »