Ed: I see what appear to be good voltages from the mothor board into the A17 video driver board, that is Gnd, +12VDC, V Sync, HSync, and video (Intensity)
Have a possibly good A17 board, on the bench along with a CRT, removed from instrument. Am testing voltages, waveforms, and Electrolytic Cap values for base line. It functions with just +12V drive from bench supply. I have a raster scan that varies in intensity with voltage level (0-5v) applied to video input. Have two more (not good) boards, with some known bad caps, that then can then be repaired to the baseline. Will then try A17 and CRT on the 5372A itself. Lester B Veenstra K1YCM MØYCM W8YCM 6Y6Y les...@veenstras.com 452 Stable Ln (HC84 RFD USPS Mail) Keyser WV 26726 GPS: 39.336826 N 78.982287 W (Google) GPS: 39.33682 N 78.9823741 W (GPSDO) Telephones: Home: +1-304-289-6057 US cell +1-304-790-9192 Jamaica cell: +1-876-456-8898 -----Original Message----- From: time-nuts [mailto:time-nuts-boun...@lists.febo.com] On Behalf Of ed breya Sent: Tuesday, June 30, 2020 4:40 PM To: time-nuts@lists.febo.com Subject: Re: [time-nuts] FW: HP-5372A operation with no CRT display. Looking back at the OP, it appears the display is at least partially working, since there is some HV to light a dim spot on screen. I don't know what this display looks like inside, but imagine it's one or two small boards mounted open-frame on the CRT mechanical assembly, and connected to the instrument by one or two cable/connector assemblies. It should be possible to remove the whole thing onto a bench, and run it out in the open for better access. The first thing to do is close inspection, looking for any obvious problems like puffy or leaky capacitors and burnt parts, loose/broken connections, and possibly fuses open. Power supply problems are the most likely culprits, so if you can figure out the internal power distribution at least somewhat, you can make some measurements. These kind of units likely run on a single bulk supply at a standard voltage like +12 (most likely since most magnetic raster CRTs use 12V heaters) or +24, and you should be able to find out from the schematics for the rest of the system. Are the signals in the interconnections labeled? If so, the power should be identified, and also try to figure out what each signal is supposed to do. You already know the sync and video, etc, but also look for anything else like an enable or standby signal. What I'm getting at here is that depending on the overall supply architecture, when the 5372A is in standby (keeping the OCXO on) it could be that a lot of stuff is actually powered, but disabled. Related to this, is there a GPIB or other command that can turn off the display and lock out the front panel when in remote-only mode? If there is some form of on/off provision, a signal failure here could shut it down even if the rest is OK. There are lots of possibilities, but it narrows it down a lot if you can proof the supplies and external controls. Ed _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.