FET ratings needed for MX705 monitor

[berniedd]

I'm an amateur hobbyist trying to fix a friend's dead MX705 17-inch CRT monitor. It's made by Top Victory Electronics (Chinese) but Hewlett Packard badged. I found and replaced a shorted HOT. The green LED at the front panel now glows on powering up but I don't get high voltage nor the static discharge from the CRT front face. Connecting a working computer to the VGA input, I measure only 60 volts instead of the normat 200 volts at the HOT collector. It comes from a boost circuit from the low voltage chopper before the flyback. There is a large inductor in series with the rectified output from the low voltage chopper transformer. Beyond this inductor there is a power FET whose source lead goes to ground (drain lead connects to the inductor).Then we have a big diode that goes to the flyback primary. The FET gate is excited by what appears to be a lead coming from a long IC near the yoke connector pins. I can't see the IC marks because it is covered by a protective metal plate. I replaced all 3 large filter electrolytics along the boost pathway but still no dice. I now know the flyback's OK as I got high voltage from it when I had it tested externally with a FBT tester. I'm beginning to suspect the FET is open circuit but I'm having difficulty getting an exact replacement. The marks on the IC are as follows: D8N*25 GK13Y VW CHN502 (where * looks like a Z that's printed backwards). I can't get anything about it off alldatasheet.com nor datasheet4u.com. There's no listing for anything even remotely near those letters/numbers. What type replacement or rating should I use? Thanks for the help extended, guys.

By the way, I scoped the the output of the horizontal driver. After connecting a working computer to the monitor's input, I saw at the output lead of the horiz driver transformer a 31,250 hz 5 volt signal that looked like a rectified sine wave without the negative excursions. I also checked and found the HOT snubber diodes and capacitor to be OK.