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  #16  
Old 10-23-2013, 09:27 PM
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N2IXK N2IXK is offline
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This could be explained by the tubes drawing twice as much current on the various anodes, and shifting the voltages on the resistive divider network accordingly. Not really a meaningful data point, I'm afraid...
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  #17  
Old 10-23-2013, 10:27 PM
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I suspect that is what's happening. One way is to confirm by trying that experiment again and measuring the voltages.

In a way that leads me to suspect that if the 5ADP* CRTs are indeed bad it may have something to do with the focus electrode.
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  #18  
Old 10-23-2013, 11:03 PM
bob91343 bob91343 is offline
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I have what I believe to be a good 5ADP1 if anyone is interested.
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  #19  
Old 10-24-2013, 11:52 AM
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This is a very long shot, but I ran in to it on a DC-coupled scope many years ago.

Measure your CRT voltages both with and without a signal applied to the vertical input.

If anything except for the deflection plate voltages change, suspect something is amiss in the DC coupled sweep amplifier that causes it to pull too much current and create a power supply voltage drop that is causing the CRT to go out of focus.

Jas.

Last edited by earlyfilm; 10-24-2013 at 11:56 AM.
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  #20  
Old 10-24-2013, 03:53 PM
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I can try that, but why would the 5CP1A CRT not go out of focus and why would two identical scopes have the same exact problem?
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