Re: [volt-nuts] 3458A reference boards on ebay
RE: "One seller, with the two high stability reference boards at $750, claims that they come from working and recently calibrated 3458As. Why would anyone wreck a working and recently calibrated 3458A? " Some contracts may require the more stable reference and the standard reference is pulled to make room for the option 002. I know I have done that at lest 30 times. On Thu, Jan 29, 2015 at 12:59 PM, Dr. David Kirkby (Kirkby Microwave Ltd) < drkir...@kirkbymicrowave.co.uk> wrote: > On 27 Jan 2015 09:47, "Orin Eman" wrote: > > > > There is a seller letting a slow trickle of them out there... they seem > to > > be going for about $165. The current batch of two is around $100, but > will > > probably be bid up. > > I am puzzled why there are so many reference boards that are supposed to > come from 3458As on the used market. It makes me wonder if they are > genuine. > > One seller, with the two high stability reference boards at $750, claims > that they come from working and recently calibrated 3458As. Why would > anyone wreck a working and recently calibrated 3458A? > > It is not beyond the bounds of possibility that a 3458A might be worth more > in parts than as a complete unit. I know this is true for some HP items, > but I doubt that is the case with a 3458A. > > Another seller, who has them at $395 "or offer", has sold 17 and has 11 > left. > > Although expensive, having two and monitoring the difference between them > would probably allow their stability to be measured with a DVM of modest > specification. > > There are lots of counterfeit components around, and I fear that it could > be some of these boards could fall into that category. This makes the > building a board from new components more attractive. In the short term it > is likely to be less stable than an old reference, but at least one would > know the history of it. If the components were sourced from reliable > sources, it would get around the potential counterfeit problem. > > Dave. > ___ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > -- *John Phillips* ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] 3458A reference boards on ebay
On 27 Jan 2015 09:47, "Orin Eman" wrote: > > There is a seller letting a slow trickle of them out there... they seem to > be going for about $165. The current batch of two is around $100, but will > probably be bid up. I am puzzled why there are so many reference boards that are supposed to come from 3458As on the used market. It makes me wonder if they are genuine. One seller, with the two high stability reference boards at $750, claims that they come from working and recently calibrated 3458As. Why would anyone wreck a working and recently calibrated 3458A? It is not beyond the bounds of possibility that a 3458A might be worth more in parts than as a complete unit. I know this is true for some HP items, but I doubt that is the case with a 3458A. Another seller, who has them at $395 "or offer", has sold 17 and has 11 left. Although expensive, having two and monitoring the difference between them would probably allow their stability to be measured with a DVM of modest specification. There are lots of counterfeit components around, and I fear that it could be some of these boards could fall into that category. This makes the building a board from new components more attractive. In the short term it is likely to be less stable than an old reference, but at least one would know the history of it. If the components were sourced from reliable sources, it would get around the potential counterfeit problem. Dave. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] [Bulk] Re: 3458A reference boards on ebay
Well, sounds like you already prepared against some of my suggestions. Still there are possibilities to troubleshoot it - i cannot neither see that you checked everything I listed nor that my list is complete and you had much bigger ideas. The datasheet gives some figures telling how much some influences, like R variations (and as a result I variations) get supressed on the output - I would go hunting for nodes where the noise bursts are biggest if all preventive actions failed. Up to a certain point, troubleshooting is fun. Hendrik Am 29.01.2015 18:22, schrieb Randy Evans: The reference module is in a metal box and uses an external linear PS with internal separate regulation. I don't think its external EMI, but anything is possible. Randy On Wed, Jan 28, 2015 at 10:28 PM, Hendrik Dietrich wrote: Am 29.01.2015 04:07, schrieb Randy Evans: I bought two HP-3458A ref boards from John Daly (he no longer has any more) and they worked fine but have intermittent noise bursts. I suspect they were rejects from HP/Agilent. At some point I will probably replace the LTZ1000As and reduce the internal temperature set point for better stability. Has anyone else had any issues with these units? BTW, I packaged the units in an enclosure for a stand-alone reference and, except for the occasional noise bursts, seem very stable according to my HP 3458A and fluke 732A/ESI RV722 KVD. Randy Hi Randy, Noise bursts, especially if they get back on track again, sound like electromagnetic interference from your short description. If applicable, turn of the CFL or LED lighting, replace the switch-mode power supply with a linear one or even better a battery, try a known non-reject in place of the ebay reference module, spread some capacitors on/around the module and/or invest in a metal box. Hendrik ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] [Bulk] Re: 3458A reference boards on ebay
The reference module is in a metal box and uses an external linear PS with internal separate regulation. I don't think its external EMI, but anything is possible. Randy On Wed, Jan 28, 2015 at 10:28 PM, Hendrik Dietrich wrote: > > Am 29.01.2015 04:07, schrieb Randy Evans: > >> I bought two HP-3458A ref boards from John Daly (he no longer has any >> more) >> and they worked fine but have intermittent noise bursts. I suspect they >> were rejects from HP/Agilent. At some point I will probably replace the >> LTZ1000As and reduce the internal temperature set point for better >> stability. Has anyone else had any issues with these units? >> >> BTW, I packaged the units in an enclosure for a stand-alone reference and, >> except for the occasional noise bursts, seem very stable according to my >> HP >> 3458A and fluke 732A/ESI RV722 KVD. >> >> Randy >> >> > Hi Randy, > > Noise bursts, especially if they get back on track again, sound like > electromagnetic interference from your short description. > If applicable, turn of the CFL or LED lighting, replace the switch-mode > power supply with a linear one or even better a battery,, try a known > non-reject in place of the ebay reference module, spread some capacitors > on/around the module and/or invest in a metal box. > > Hendrik > > > > > ___ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/volt-nuts > and follow the instructions there. > ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
