I have HP 853A mainframe with HP 8557B (the 75 ohm version) plug-in. The 853A CRT has no display light output at all, at any intensity/focus setting. If I plug an external scope set to X-Y display into the rear X-Y outputs, the analyzer plug-in appears to be functioning normally (and the same plug-in works fine in another 182 mainframe.)
I've downloaded manual 00853-90010 and checked DC voltage test points on A3 (all were in spec), then went to section 5-13, and with a Tektronix P6015A 40 kV 1000:1 scope probe, I verified HV cathode (test point A4TP1) is close to the voltage marked on the module (-2467 volts). Step 5-13-8 it tells me to measure A6TP2 (which I think is a typo; there is a test point on A4 called A4TP2 and after this test point is checked, instructions tell me to put the cover of the HV section back on.) A4TP2 measures 27.3 volts at any setting of the front panel intensity control (the text in section 5-13 step 8 specifies 30.0 +/- 0.2 volts, and tells me what to do if the voltage is too high, but not too low.) I tried setting the 8557B to manual sweep to get a dot on the display, but no light seen. As the manual at this point anticipates that the CRT should be emitting light (and is mostly worried about too much intensity), I think I'm not looking in the right place.
Any idea where to look next?
Thanks!
