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HP8756A possible CRT subs?

ed breya All Messages By This Member #151796 I fired up this 8756A I've had for many years and never used because it didn't seem to work. The CRT is very dim and with poor focus. I tried to tweak it up a bit by guessing at various pots in the display module, with little improvement. I think the CRT is at its EOL. ? I can't find any (free) service manuals or info to work on it or even ID the CRT, and I don't think it's worth buying any since I'm very near to getting rid of it anyway, unless I see some potential goodness. ? Does anyone happen to know if the CRT is the same as in the 8566's IF/display unit (85665 I think)? I have some of these so it might be any easy swap if so, then I could see if it can be fixed. The faces appear to be the same size, and both are electrostatic deflection with drawn graticules, and similar application, so it would make sense to use the same CRT. I know that the over the years the 8566 displays had two different possible CRTs (and support HV circuitry) used - I'm hoping for either one to be a possible sub. ? Ed ? ?
tom_iphi All Messages By This Member #151797 Hi Ed, ? ever thought of regenerating the CRT cathode? Might be easier than replacing the unit. ? Tom
Robert G8RPI All Messages By This Member #151799 What would you use a scalar analyser for these days? The only place I've seen them still in use in recent years is older microwave antenna measurement ranges. Those were old existing facilities. ? Robert.
ed breya All Messages By This Member #151800 Yes Tom, I have done CRT rejuvenation before with some success. About ten or so years ago I did experiments on some junkers, and an actual fix on a Tek 576 CT that's still working well. ? I was hoping to not have to fool around with all the details and grief, just doing a quick swap and see what happens. ? After some more investigation I found that the 8756A uses an HP-made OEM type display - a 1345A apparently. I have found the manual for that, so now I can at least work on the display aspects. It's quite complicated with built-in digital storage, vector drawing, and character generation. With proper info (and time and patience) I can find out what the deal is - maybe the CRT is OK after all, just way out of adjustment or with a part failure in the circuits. At least I should be able to ID the CRT now and compare against ones in other HP gear, just in case. ? Ed
Harke Smits All Messages By This Member #151801 开云体育 Easy: if you do not have a vna to 20+ GHz for example. Like me.... I use it quit often. Harke On 10/05/2025 21:29, Robert G8RPI via groups.io wrote: toggle quoted message Show quoted text What would you use a scalar analyser for these days? The only place I've seen them still in use in recent years is older microwave antenna measurement ranges. Those were old existing facilities. ? Robert.
Jeff Kruth All Messages By This Member #151802 Interesting. Scalars are MUCH quicker to use and my first choice. I have 8720, 8510C, 8722A, even old 8410C stuff, but I hardly use them because I rarely need to measure phase. My go -to is an 8757C with a 83650A sweeping synthesizer - most handy with a plotter to capture S21 work. VNA's are great, but tedious. Jeff Kruth In a message dated 5/10/2025 4:22:15 PM Eastern Standard Time, yrrah@... writes: ? Easy: if you do not have a vna to 20+ GHz for example. Like me.... I use it quit often. Harke On 10/05/2025 21:29, Robert G8RPI via groups.io wrote: What would you use a scalar analyser for these days? The only place I've seen them still in use in recent years is older microwave antenna measurement ranges. Those were old existing facilities. ? Robert.

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