[Chad Hauris]

Here are some additional suggestions:

1. Use a neon bulb tester to check for AC high voltage. Hold the
bulb (attach to a pen or other non-conductive device if needed to keep the HV leads away from your fingers) against the insulation of the HV output lead (plate lead of rect.) and the horizontal output tube--no direct connection. There is enough RF radiation from the leads to light the bulb if there is AC HV.

2. If no AC HV is indicated, remove the plate cap from the horiz. output tube. Attach the voltmeter to the disconnected plate lead. You should get the B+ voltage. If you do, the damper and flyback are working well enough to pass DC plate voltage on to the tube.

3. If plate voltage is indicated at the HO tube then hook the plate lead back up and measure the negative grid voltage. No negative grid voltage equals no input signal from the oscillator.

If none of this turns up anything then I would check the flyback w/ohmmeter...from the horiz plate lead to the HV plate lead is usually 400 ohms.

Another thing I do is to use a lamp bulb in the HO cathode circuit--from cathode to ground...a 200 MA 6.3 volt if I remember correctly. This will act as a fuse if there is a heavy overload and also allows you to set the cathode current in sets with horizontal efficiency coils by adjusting for minimum lamp brightness. If the lamp is positioned where you can see it glow through the back, you can also check it periodically and therefore detect abnormal increases in current by an increase in lamp brightness.

I think the biggest cause of flyback fry-ups is excessive HO current. Sets made in the 60's generally have no overcurrent protection in the HO circuit. A lot of 50's sets have a fuse in series with the damper and some 70's sets use a thermal fuse, circuit breaker, or more rarely a fuse in the HO cathode circuit.