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Personally I like to do voltage checks rather than component checks. Improper DC voltages in a circuit will point you in the direction of the bad component. A lot of the time the old electrolytics are fairly good, but it is the paper caps that need to be replaced. Shorted bypass caps can damage other parts such as resistors...this often results in no plate voltage to a tube. It only takes ONE bad cap in the "wrong" place to completely disable a stage.
Remember that power supply filter problems will cause hum in the speaker even if the volume is down. If the hum can be shut off by turning down the volume the trouble is likely somewhere else. Maybe a cap shorted in the sound IF or discriminator stage and took out a plate load resistor, causing a stage to be inoperative.
A trick for vertical testing is to take 6.3 vac filament voltage (the ungrounded side) and hook up a .047, or .1 or so 600 volt cap. This prevents high voltage from going back on the filament lines. Take the other end of the cap and hook it to the grid of the vert. output stage. If you get vertical deflection then the output stage is ok. Then move it back to the grid of the oscillator stage. If you get deflection here, the tube is getting voltage but there is a problem with the feedback loop causing the oscillator to not oscillate. This method has helped me find vertical problems that appear tough at first.
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