I got a HP8754A recently that mostly works but seems low on available trace intensity. Maybe it just needs some internal adjustment, or maybe the CRT is weak on emission. Now that I have this one, I've cancelled a project I was planning to fix an old HP8407 VNA with 8412A CRT mag/phase display. I junked it all out and it turned out to be the right choice, since I found all sorts of corrosion in places inside, and broken items, which would have been a PITA to restore anyway. I would have also needed to acquire or build a suitable source for it. The 8754A has everything in one unit sufficient for mag/phase transmission measurements on RF parts. It will be committed to the component testing dept.
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I saved the CRT from the 8412A. It seemed to be pretty decent in brightness, so maybe it could be a spare for the 8754A if ever needed, with certain limitations. The screens appear to be basically the same except for marking details, and the 8412A one does not have the circular or radial graticule lines for polar display. In the manuals I found the CRT pinouts appear to be the same, but the listed cathode supplies differ by 100V - could just be typos, or different design choices, or maybe due to different phosphors (P39 v. P7?).
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I believe they are both the same basic CRT, just with different faces, so should be interchangeable. I found some CRT info here in the files department. It says the 8412A used 5083-9081/P7, and the 8754A used 5083-1890/P31. The manual for the 8754A says its standard CRT is P39, while the 8407A doesn't say anything about the phosphor. I know they're both green, and would have gone with long persistence for this application. Anyway, I can accept the differences if something should happen to the original CRT, and the spare is close enough.
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Does anyone know details of the HP CRT lines, or where more info can be found to clearly determine (electrical) interchangeability?
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Ed
