Re: Tektronix 465 No Trace, No Dot


On 11 Apr 2016 13:19:10 -0700, you wrote:


Vertical and Horizontal deflection plate voltage: If this were too high or too low (i.e., "very negative"), the beam would deflect into the plate or off-screen, correct? What's a reasonable range, differential, between a set of plates? I seem to remember applying 20 volts in my undergraduate physics class to a CRT on a table.
For the horizontal plates it is about +/- 80 volts differential for
full deflection. For the vertical plates it is about +/- 32 volts
differential for full deflection. These numbers can be worked out
from the schematics, control settings, and waveforms shown in the
service manual. Maybe someone can double check me on this.

With no input, a single channel active, and a slow sweep speed, a
voltmeter can be used to verify that the horizontal and vertical CRT
outputs are doing what they are suppose to do.

CRT Heater voltage: Is there an easy-access test point for this 6.3 volt AC point? Should I try and read the current too? Or maybe ohm it out? Barring the above, time to check the cathode and anode voltage, correct? Thanks very much. The last scope I took apart had tubes in it and was larger than a mini fridge, so I really appreciate any insight you folks might have.
The resistance will be the safest thing to measure.

Check fuse F1419 on schematic 10.

If you have a secondary working oscilloscope, the collector of Q1418
on schematic 10 will show if the high voltage inverter is operating.
Another good way to test the inverter is measuring the voltage at the
collector of Q1404; it will be much lower than the indicated +4.4
volts if there is no negative high voltage cathode supply.

I would not bother checking the anode voltage for now since the
oscilloscope will show a recognizable display without it.

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