Products > Test Equipment
HP 8566B - What to look for?
W4PJB:
Well, mine has a .gov tag on it, so it was probably used twice, put in a storage facility for 30 years, then went to auction for pennies on the dollar :-DD
G0HZU:
My HP 8568B was also a govt owned analyser. The govt donated it to the company when it was about 1 year old.
They also donated a nearly new Advantest TR4172 analyser a few years later and this would have cost them about $60k due to the high cost of the Yen in the late 1980s.
I also now own that Advantest analyser as the company gave it to me about 20 years ago. I had to make a charitable donation for it though. It was a worthy competitor to the HP 8568B. It wasn't as polished as the 8568B in terms of all round performance, but it outclassed it for spurious free dynamic range. That's why it was donated to the company. The 8568B was good, but in terms of SFDR it wasn't good enough for the stuff we were doing for govt back then. The TR4172 also had really low phase noise at 100kHz offset. IIRC it was typically about -128dBc/Hz. It also had a tracking generator and could be used as a crude VNA with an external RL bridge.
If you can get that 8566B fully working, you could probably sell it to a collector for a lot of money as it looks to be in fantastic condition inside.
W4PJB:
Since it looks like I'll be working on the CRT power supply section, any advice on how to ~not~ kill myself? :scared:
Just kidding... mostly. I'm very aware of the voltage levels in CRT circuits, even potentially when unplugged. Do the HP CRT boards typically have bleeder resistors to discharge the capacitors when unplugged? I see nothing in the service manual instructing to manually discharge anything, or wait "x" time before servicing; it simply states to not work on this area of the unit with the power cable connected. I could always cobble together a drain circuit to discharge it in a controlled manner, but it isn't exactly easy to get to HV lead on the CRT on these units.
Thanks!
KE5FX:
--- Quote from: W4PJB on June 12, 2024, 02:26:18 am ---Since it looks like I'll be working on the CRT power supply section, any advice on how to ~not~ kill myself? :scared:
Just kidding... mostly. I'm very aware of the voltage levels in CRT circuits, even potentially when unplugged. Do the HP CRT boards typically have bleeder resistors to discharge the capacitors when unplugged? I see nothing in the service manual instructing to manually discharge anything, or wait "x" time before servicing; it simply states to not work on this area of the unit with the power cable connected. I could always cobble together a drain circuit to discharge it in a controlled manner, but it isn't exactly easy to get to HV lead on the CRT on these units.
Thanks!
--- End quote ---
It is indeed described in the manual:
It's worth following this procedure, as the CRT really will hold a charge for quite some time. Contact with this voltage probably will not kill you but it will hurt. :)
Be sure the CRT shield ground wire is in place. How I know this is a long and boring story, but trust me.
All of that being said, whatever went 'poof' and smoked is probably not in the HV section.
W4PJB:
Edit: Now that I knew what to look for, I found the procedure in a different manual from EMCTEST. Thank you for sharing this!
Also, the manual from EMCTEST is a 1990 printing, so likely more representative of my unit, rather than the 1984 printing from Artek, so added bonus.
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Thank you for your reply. Two things I find interesting here:
1: My manual is completely different, and does not list this procedure at all.
2: HP engineers advise using the wire on a screwdriver trick on a sensitive $60,000 piece of RF equipment :D I would have expected something a bit more.... controlled.
I'll post below the only two pages in my manual that reference a service procedure for the A1A3 or the CRT. The only place I see a reference to a discharge procedure for a high voltage in the A1 section is in the A1A8 section, where it advises, "The time constant of the filter capacitor circuit is about 25 seconds. Before servicing, allow adequate time for discharge after line power cable is removed.". But this is referencing mains voltage levels, not the HV circuit. Even the CRT removal procedure does not have any flags about HV.
Was your manual sourced online? I'm using a manual from Artek, and the page numbers for the A1A3 stop at "A1A3 9/10", which is the schematic diagram for this board. I don't see it in the manual on Xdevs, either.
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