Fortune 1 Video Board Blowing Fuse

[Gunk]

Howdy,

Have an F1 (I think) that's currently hard broke.  Starting with getting the CRT up and running so I can diagnose the rest. The large, ceramic resistor (15W/220 ohm) on the 1401 board was trashed/crumbled.  Hard to find but finally got a few from China I suppose.  Fuse was wrapped in foil, go figure.  Replaced resistor, fuse, and all capacitors.  No apparent lifted traces or bad solder joints.  Board very clearly got hot at some point (see pics).  Fuse blows and of course no screen.  Any ideas on what next?  Thanks 

[Badbaud]

That is a RGB monitor board. Suspect the transistors and regulators on the heatsink and the large flyback drive transistor and the diode in front of it.
Finally check the fullwave bridge for a shorted diode inside.

[Chris-socal]

My personal experience with RGB1401's is not the best, most of them have a lot of heat damage. You can find 220 ohm or 225 ohm resistors no problem, either is fine. But the wattage does need to be 15W or higher.
Exactly what Badbaud said, check all those transistors for shorts using the diode setting on your DVM. None of the legs should read completely shorted to another. Also, look VERY closely at traces on the bottom of the board. Once they get hot like that you get broken traces that you cannot find without a magnifier. I don't care how young or good your eyes are, the traces break right at the base of the solder joint and they look perfectly fine. The last one I worked on had several broken traces and solder joints on components that looked like they were connected but they were not.

If the flyback is shot you are probably out of luck.

Chris