Tektronix 465B -- No trace for half the display

[rtg72a]

Hi, I was given a Tektronix 465B in an "as-is" condition. Upon turning the unit on and hooking it to its internal calibrator, I get this:



Does anyone know what could be causing this? Any advice would be appreciated.

Regards!
rtg72a

 

[andre_luis]

Near to the botton-right corner of the screen, there is a position adjustment knob.
Just turning it few turns in clockwise, nothing happens ?

 

[BradtheRad]

Ordinarily the horizontal position knob should cure it. However that probably will not be sufficient, since that's probably the reason the owner got rid of it.

Doubtless the internal circuitry (horizontal plate voltage) needs adjustment. .

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Try turning off the sweep. Turn on X/Y plot. Apply voltages in an effort to bring the beam to the right side of the screen.

 

[rtg72a]

andre_teprom: I have tried that. Adjusting the position knob actually makes the trace go towards the left, and the trace will eventually be off the display.

BradtheRad: Putting the scope in X/Y mode gives me this:

 

[Warpspeed]

Hmmmm....
I have a 465B and its a rather complex beast.
But on the other hand second hand spare parts, whole circuit boards and sub modules are pretty much available and reasonably affordable.

Looking in the 465B service manual trouble shooting flow chart it says:

"Trace off centre horizontally"
"Check Q4455, Q4465, Q4481, Q4482, U4491"
Then,
"Trouble shoot horizontal amplifier" And that is all it says.

The above transistors and flip flop all have to do with selecting sweep A or sweep B. Everything, including X/Y mode appears to have the horizontal shift problem, so its most likely to be on the horizontal amplifier board.

There are a LOT of different power supply rails involved with all this, and I would assume that if one of them had a problem it would have more far reaching effects than just a horizontal shift.

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[BradtheRad]

My scope has plates for horizontal position. They receive a supply of 100 V. You have some horizontal response, but apparently less than normal. And beam position is lopsided.

I believe one plate is not getting sufficient voltage. Or a bad contact might be at fault.

In addition to recommendations in post #5, you must examine the boards for test points, and see what voltage you read. Maybe it should be +100V or -100V, or something similar.