Hi > On Aug 5, 2020, at 2:55 AM, [email protected] wrote: > > > I would like to share with you my thoughts on two important points that > concern a little all attempts to modify and upgrade the equipment. > > In general I am very reluctant to modify both the electrically and > mechanically, in this case, the HP5065A. Modifying, even completely a board, > I agree if there is a significant improvement, trying to use the existing > pinout and, in the need for additional connection points, use additional > connectors on the board. As regards the space on the pcb, smd components can > be used whenever possible or doughter boards.
Indeed this has been the debate on a *lot* of equipment as it gets old enough to be considered an antique. Do you preserve it in original condition or do you keep it running ( or flying ….). Needless to say, there is a lot of debate about this. > > Remove boards, transformers or anything else I find reluctant, I would > prefer to have the possibility of being able to go back to the original > configuration if necessary. > The area occupied by the optional batteries, which I think almost nobody > uses, can be used for new electronics. > > Using a switching power supply with better performance I agree and since > there is already a dedicated DC input on the back of the 5065A I would prefer > to use the one to connect to an external box that contains the new power > supply and the management of a backup DC input. This eliminates the need to > dismantle anything inside the HP5065A. If you look at the heat generated ( = wasted) running modern <= 3.3V supply parts off of the 20V bus, multiple switchers start to look very attractive. Bringing all that in from “outside” probably isn’t the best / safest way to do it. Using some of the “open space” for a set of supplies is probably a better idea. > > Another important point is that of the certainty of the results of a > change. I mean that most hobbyists who have a 5065A, including me, do not > have the opportunity to measure the proposed improvement effects, first of > all because they do not have a reference such as an HMaser available, nor > even such a refined measuring system to appreciate the improvements made. I > want to remember that between zero and 8kseconds the GPS system (e.g. HP > GPSDO) in our laboratories has an Adev higher than that of the HP5065A and > therefore the measure we do in that range is that of GPS, not that of > rubidium. The most common solution to this is to use multiple reference sources. Finding OCXO’s that are better than a 5065 at 0.1 to 10 seconds is possible in a hobby environment. As mods are done, this is a pretty critical region to examine. A DMTD isn’t a super exotic piece of gear anymore. There are a lot of them in basements. A single mixer setup (which is even easier to build) is quite adequate for a 5065 <-> OCXO comparison. A triple channel setup (still in range for a basement project) would let you do a three corner hat. (with some range to it). If you have a three corner hat setup, the OCXO’s likely can be useful to 100 seconds. Past that a couple of fairly good telecom Rb’s could get you a bit further. There is also the possibility of running more than one 5065 … Not all parameters on the 5065 are at “near noise floor” levels. The close in ( < 20 Hz offset) phase noise is not all that great. One does not need a -170 dbc / Hz floor sort of setup to check it out. As tweaks are done, noise in this region *is* of interest. Comparison against a pretty normal OCXO would be “good enough” in this case as well. Bob > > For this reason I invite all those who dedicate themselves to these very > interesting changes proposed to test the results obtained in depth and to > share them with us with numerical and graphic elements. I take this > opportunity to thank them in advance for their scientific help. > > I want to specify that this is my point of view, it is not a rule and not > necessarily shared by other people. > > thankyou , Luciano > > Luciano P. S. Paramithiotti > [email protected] > www.timeok.it > > Da "time-nuts" [email protected] > A "Discussion of precise time and frequency measurement" > [email protected] > Cc > Data Tue, 4 Aug 2020 13:32:31 -0400 > Oggetto Re: [time-nuts] "The Penultimate HP5065 A15" > Hi > > If a more extensive rebuild is in the works ….. > > +/-20V is (as has been observed) not an ideal voltage for “modern” > electronics. > If you dig into each of the boards, there is a lot of “drop it down right > now” regulation > done on a board by board basis. More or less what might be there: > > A1 Synth > A2 Battery Charger > A3 60 MHz multiplier > A4 100 KHz divider > A5 Digital Divider (= clock) > A6 1 MHz divider > A7 AC amplifier > A8 Phase detector > A9 Integrator > A10 OCXO > A11 Rb temp control > A12 Rb assembly > A13 5 MHz buffer > A14 Logic > A15 Power supply > A16 Power for clock > A17 Terminal board > A18 Jumpers ( = alt for A2) > A19 Led Clock board > > For most uses, A4,A5,A6,A16,and A19 are not required. A2 is just a pair of > diodes (A18) rather than > a battery charger. A17 is more part of the wiring harness than anything > else. Looking at what’s left: > > A1 synth, this seems to be a target for various replacement schemes. Right > now, it has a bunch > of positive voltage rails with some circuits running on 20V. Replacement > likely would run on <= +12. > > A3 Multiplier. Again a target for replacement in some schemes. Same supply > as A1 for replacement. > Existing design runs +20 direct to a lot of circuits. > > A7 AC amplifier. Now runs +/-20V. Pretty much begs for a modern op-amp > based replacement > board. +/-12 probably is fine for that board. A *good* -15 would work for > the existing board with minor > mods. > > A8 Phase detector. Replacement probably is all digital. Now runs +20V A9 > Later version of the board runs +/-15. Probably would work fine a good +/-12 > with minor mods > > A10 If it’s a 10811, it’s going to need > +18 for the heater and +12 for > the OCXO. There are other > “at least as good” parts that work fine on +12. > > A11 Unless you want to redo the heater windings on A12, you are stuck with > +20 to +30V. Rest of the board > sort of begs for a modern op-amp approach. > > A12 Lamp assembly is the only load (other than heater windings and C > field). It does run on +20V. > > A13 +20V taken to +9 for everything on the board. Simple mod to run on +12 > (or +15 or +10 …). Replacement > likely runs on +12 > > A14 If the upstream boards get changed, this likely does as well. Sort of > begs for a $1 MCU and a handful of resistors > as a replacement. > > A15 ( the topic of discussion) > > So, there are two “customers” for -20V. Both would be happy with a fairly > good -15V instead. If the replacement > OCXO for A10 tunes 0 to 5V, the need for a negative supply becomes a bit > unclear. > > There are a couple of places you can’t easily get around 20 to 30V. The > heater windings on the physics > package are the biggie. The Rb lamp driver is probably not worth messing > with. > > If you keep A1, A3, A7, or A8, they will need the existing +20V. +12 or +15 > makes more sense for their > replacements. A13 could easily be modified and run on +12 or +15. > > ==== > > So why all this long winded yack? > > The ultimate need for +20 is really pretty small. The lamp still needs it. > The heaters need something > in that vicinity. They don’t need the super regulation or low noise that > the lamp needs. > > The -20 probably does at least as well as a -15 V supply, even as the > device sits right now. > Long term -15 makes more sense. > > A bulk +12 (and maybe +5) likely take up the heavy lifting for most of the > boards once they are > modified. Indeed they would be useful even on the existing boards. > > Does this change anything you do on the A15 right now? Maybe not. It is > worth thinking a bit on though. > > Bob > > > > > >> On Aug 4, 2020, at 6:35 AM, Poul-Henning Kamp <[email protected]> wrote: >> >> -------- >> Magnus Danielson writes: >> >>> If that is the range you aim to improve, then I strongly recommend you >>> do re-read the postings I did about phase noise in detector range, as I >>> have showed that phase-noise get's mixed down to DC and increase the >>> noise there. With very ugly and hand-wavey hack I was able to >>> significantly reduce that noise essentially by cleaning up the >>> phase-noise. >> >> Ohh, absolutely. >> >> My plan is to put a modulated DDS synth in to get a much more modern >> detector system. >> >> But right now the zener on my a15 is better at measuring temperature >> than holding voltage stable, so I'm addressing that first. >> >> See the 3rd graph here: >> >> http://phk.freebsd.dk/hacks/HP5065A/20150908_a15/ >> >>>>> I would go for the LTZ1000 if you can. The LM399 has gone out of >>>>> fashion for a reason: [...] >>>> Yes, I know, being also a volt-nut :-) >>> >>> I have not yet jumped down that rabbit-hole as I am by far not done with >>> the current one. :) >>> >>> I've been looking at the LTZ1000 and one day I may get some. >> >> You *really* want the version of it which is packaged in the attractive >> and *incredibly* useful "HP3458A" cabinet :-) >> >> -- >> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >> [email protected] | TCP/IP since RFC 956 >> FreeBSD committer | BSD since 4.3-tahoe >> Never attribute to malice what can adequately be explained by incompetence. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
