[wiseguy]

I have one of those sets, and had several over the years
you need to rsolder the pins on the CX-104 IC and anything around it that may look like cracks in the solder joints, there is also a few small Caps to replace ,the cx-104 is the horiz osc control and other things, there is a small pot to adjust h freq you need to clean it and rotate it then center it, also on the sweep section look for "GREEN" mylar type capacitors, the upgrade back then was new ones of the same value but they were Blue in color, Sony told us back then that if any capacitor is green in color it's mean, and if its blue in color its cool, in other words the blue versions were the updated ones, the green ones would short intermit and blow out the sg-613's, you should check for horiz osc by connecting a I think 15 volt Dc power supply to the test point they show in the manual and hookup a scope and look for proper waveform,
also there is a type of glue all over the board that becomes conductive and will kill the H-OSC which in turn kills the SG-613, you need to scrape off all of that brown glue on the boards,
its been a few years but I do remember servicing these things.
also that brown glue can cause the H-Freq to double and increase HV intermitly and kill the picture tube, you would hear the crack then arcing in the CRT
also this set has a HOT chassis ,use an isolation transformer when you have the cover off, anything with a ground or even a CATV connector touches the chassis will blow out the SG613's,
Good luck!
those are nice sets, really slim and flat