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Old 4th Jul 2013, 1:26 pm   #58
davidgem1406
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Join Date: Feb 2011
Location: Sheerness, Kent, UK.
Posts: 936
Default Re: Tektronix 465B Scope - Some problems.

I have now disconnected the plates from the output stages, Y1 and Y2 are joined and X1 is joined to X2.
That really hasn't changed the problem, the spot is fairly large with a lighter glow round it and will not focus down.
The focus and astig controls have much the same effect as before, just distorting the spot as shown by the images in post #39.

Don't know if putting some + voltage on the plates may help, say from the +55V rail. I seem to remember from many years ago that CRT's did not like the plates to be floating, maybe different CRT's back then.

I will put the X connections back and see what gives then.

I forgot to mention that the spot is pulsing at a regular interval. Just realised, whilst writing this, it is something picking up the timebase frequency as reducing the time period pulses the spot faster. Turn the timebase off and it stops.

May be relevant, may not.

Dave
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