Definitely K4900 series. Model will be 19K49xx or similar. Cap kit is always a good idea, but start with the fuse near the AC line in. If that's good, perform a diode test on the HOT (bottle cap transistor on the RH side - TEST W/O POWER). If case-gnd is not open, the HOT is dead. If the HOT is dead, the fly may be as well.
Repeat diode test (case-gnd) with the voltage regulator on the left hand side. If it's open, test B+ next. For that, look at your picture where it says "FACE". Near that will be a test point (TP 9, IIRC) for your B+. Check that with the monitor running (be careful), it should be 123V to gnd for a 19" and 130V for a 25" tube. If not, your VR may be dead anyway. Start troubleshooting the power supply section until you have proper B+ at TP9